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Thin Film Partnership Program

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Amorphous and Thin-Film Silicon

Search the Thin-film Resource Database for more articles, news, and reports.

Amorphous silicon (a-Si) was heralded as the "only" thin-film PV material in the 1980s; a decade later, many people wrote it off for its instability and low efficiencies. Multijunction cell configurations have helped solve these problems. In the near term, look for modules with 6% to 8% efficiencies, as well as the construction of multi-megawatt a-Si facilities.

Press Releases, Articles, Pictures/Tables/Figures, Other Items

Journal Articles

Conference Papers

Post Date	05/30/2008
Title	THE ROLE OF POLYCRYSTALLINE THIN-FILM PV TECHNOLOGIES IN COMPETITIVE PV MODULE MARKETS
Link	(PDF 351 KB) Download Acrobat Reader.
Authors	B. Von Roedern, H. S. Ullal
Description	This paper discusses the developments in thin-film PV technologies. It provides an outlook on future commercial module efficiencies achievable based on today?s knowledge about champion cell performance. It also provides a relative cost comparison of thin-film and wafer/ribbon based Si PV modules. In 2007, about 65% of the modules produced in the US were thin-film modules when amorphous silicon modules are also considered.
Venue	Presented at the 33rd IEEE PVSC Conference, San Diego, CA 05/12-16/2008
Source	National Renewable Energy Laboratory
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	05/2008

Post Date	09/28/2007
Title	THIN FILM CIGS AND CDTE PHOTOVOLTAIC TECHNOLOGIES: COMMERCIALIZATION, CRITICAL ISSUES, AND APPLICATIONS
Link	(PDF 725 KB) Download Acrobat Reader.
Authors	H. S. Ullal, B. Von Roedern
Description	We report here on the major commercialization aspects of thin-film photovoltaic (PV) technologies based on CIGS and CdTe (a-Si and thin-Si are also reported for completeness on the status of thin-film PV). Worldwide silicon (Si) based PV technologies continues to dominate at more than 94% of the market share, with the share of thin-film PV at less than 6%. However, the market share for thin-film PV in the United States continues to grow rapidly over the past several years and in CY 2006, they had a substantial contribution of about 44%, compared to less than 10% in CY 2003. In CY 2007, thin-film PV market share is expected to surpass that of Si technology in the United States. Worldwide estimated projections for CY 2010 are that thin-film PV production capacity will be more than 3700 MW. A 40-MW thin-film CdTe solar field is currently being installed in Saxony, Germany, and will be completed in early CY 2009. The total project cost is Euro 130 million, which equates to an installed PV system price of Euro 3.25/-watt averaged over the entire solar project. This is the lowest price for any installed PV system in the world today. Critical research, development, and technology issues for thin-film CIGS and CdTe are also elucidated in this paper.
Venue	22nd EC PVSEC, Milano, Italy Sep 3-7, 2007, paper presented
Source	National Renewable Energy Laboratory
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	09/2007

Post Date	01/03/2008
Title	EFFECT OF SURFACE PASSIVATION ON SI HETEROJUNCTION AND INTERDIGITATED BACK CONTACT SOLAR CELLS
Link	(PDF 69 KB) Download Acrobat Reader.
Authors	U. Das, R. W. Birkmire
Description	Excellent surface passivation (?eff > 1 msec) and high VOC in SHJ cells are achieved by both RF and DC plasma process with hydrogen dilution. Any epitaxial / nanocrystalline growth of i-layer reduces ?eff and cell VOC. The structure of deposited thin Si:H layers strongly depend on the Si substrate orientation. The front emitter SHJ cell efficiency approaching 19% with VOC of 694 mV was achieved on textured Cz wafer using DC plasma deposited i-layer. The exploratory heterojunction cells in IBC structure reveals importance of surface passivation in the rear to achieve high VOC (683 mV) and JSC but demands further optimization of i-layer for improved carrier transport across it and cell FF.
Venue	Institute of Energy Conversion, U. Delaware. Presented at the 17th Workshop on Crystalline Silicon Solar Cells & Modules: Materials and Processes (Vail, Cascade Resort, Vail, CO, Aug. 5 ? 8, 2007).
Source	University of Delaware
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	08/05/2007

Post Date	05/30/2007
Title	METASTABLE DEFECT FORMATION IN TRITIATED A-SI:H
Link	(MS Word 128 KB)
Authors	G. A. Williams, P. C. Taylor
Description	We have shown direct evidence for the diffusion of hydrogen to heal the production of a large density (approximately 10^21 cm^-3) of silicon dangling bonds in tritiated a-Si:H,T. Some of the network healing mechanisms, which follow tritium decay, are essentially athermal and occur even at very low temperatures.
Venue	paper from the DOE Solar technology Review Meeting, Denver, CO 04/17-19/2007
Source	University of Utah
Document Type	Conference Papers (Word document)
Resource Date	04/2007

Post Date	10/11/2007
Title	DEPENDENCE OF THE ELECTRONIC PROPERTIES OF HOT-WIRE CVD AMORPHOUS SILICON-GERMANIUM ALLOYS ON OXYGEN IMPURITY LEVELS
Link	(PDF 113 KB) Download Acrobat Reader.
Authors	J. D. Cohen, Y. Xu, A. H. Mahan, H. M. Branz, S. Datta
Description	We report the effects of intentionally introducing up to ~ 5×10^20/cm^3 oxygen impurities into hydrogenated amorphous silicon-germanium alloys (of roughly 30at.% Ge) grown by the hot-wire chemical vapor deposition (HWCVD) method. Deep defect densities determined by drive-level capacitance profiling (DLCP) indicated a modest increase with increasing oxygen content (up to a factor of 3 at the highest oxygen level). Transient photocapacitance (TPC) spectra indicated a clear spectral signature for an optical transition between the valence band and an empty defect level, with an optical threshold around 1.3-1.4eV. This feature becomes stronger as the concentration of oxygen is increased. This transition results in a negative contribution to the TPC signal, and this initially led us to believe that the bandtail for the higher oxygen samples was much narrower than it actually is. Surprisingly, this additional oxygen related defect level appears to have only a very minor effect upon the estimated minority carrier collection fraction. The effects of light-induced degradation upon some of these oxygen contaminated samples were also examined in detail. We infer the existence of a significant thermal barrier to explain the observed spectral signature of this oxygen impurity defect.
Venue	MRS Spring Meeting 04/2007, San Francisco
Source	University of Oregon
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	04/2007

Post Date	04/30/2007
Title	OUTDOOR MONITORING AND HIGH VOLTAGE BIAS TESTING OF THIN FILM PV MODULES
Link	(MS Word 64 KB)
Author	N. G. Dhere
Description	Limitations of accelerated testing to predict all possible degradation modes and mechanisms in the photovoltaic PV modules necessitate that actual outdoor monitoring and testing of PV modules be performed out-doors. For this reason, thin film PV modules from leading US thin film PV manufacturers namely, First Solar (Glass/CdTe/Glass), Shell Solar Glass/CIS/Glass), Shell Solar New (Glass/CIGS/Glass), United Solar (a-Si:H on flexible substrate), Energy Photovoltaics (Glass/a-Si:H/Glass) and Global Solar (CIS on flexible substrate) with additional one crystalline silicon module are being tested. The goal is to assess their performance in the hot and humid climate of Florida and to correlate the PV performance with the meteorological parameters namely, solar irradiance, temperature, relative humidity, wind speed, etc. Statistical data analysis of the recorded data is carried out on a daily basis and on a monthly basis with PVUSA type regression analysis. Current-voltage characteristics (I-V) of module arrays taken on a regular basis complement the results obtained with continuous data monitoring. Moreover, high voltage bias testing of the modules is carried out to study behavior of leakage currents and detect any packaging material and processing flaws and consequently the module reliability.
Venue	DOE Solar Technology Review Meeting, Denver, CO, 4/17-19/2007
Source	FLorida Solar Energy Center
Document Type	Conference Papers (Word document)
Resource Date	03/2007

Post Date	10/26/2006
Title	BOS COST SAVINGS NEEDS AND POTENTIAL FOR LARGE SCALE GROUND BASED PV SYSTEMS UNTIL 2010
Link	(PDF 495 KB) Download Acrobat Reader.
Author	M. Bachler
Description	More and more large scale ground based systems were implemented with thin-film modules in the past years in Germany. Based on module pricing thin film modules appear to be very attractive for this type of application. However there are quite significant differences in balance-of-system (BOS) costs within different c-Si and thin film (TF) module types, which have a high impact on total system costs. The BOS cost portion is significantly higher for systems with TF modules compared to c-Si modules. Existing c-Si modules and BOS components were developed and optimized to achieve cost savings in the past decades already a lot. TF modules as well as the related BOS components are at the very beginning of this development so the cost saving potential ? especially for BOS costs is considered to be significantly higher for TF module based systems. Since a 6.5% degression in the feed-in tariff is required in the German EEG for ground based systems a high cost reduction pressure is imposed on total system costs. The results of BOS cost savings achieved already will be demonstrated for a sample thin-film module.
Venue	Dresden World Conference
Source	Phonix SonnenStrom AG
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	09/2006

Post Date	05/22/2006
Title	TECHNOLOGY CHOICE AND THE COST REDUCTION POTENTIAL OF PHOTOVOLTAICS
Link	(PDF 116 KB) Download Acrobat Reader.
Authors	J. E. Trancik, K. Zweibel
Description	We use a combination of system component analyses and individual experience curves for crystalline silicon (x-Si) modules, thin-film (TF) modules, and the balance of system (BOS) components, to compare future growth scenarios for photovoltaics (PV). The growth rates of TF and x-Si technologies are varied, while overall PV growth is held constant at 30%. For each of these scenarios, we estimate the total investment required for PV to reach a break-even point with fossil fuel based generation; and we investigate the intrinsic/lowest achievable costs from an analysis of potential materials, processing, and efficiency improvements. Our results show that a high growth rate (50 to 70% per year) of new technologies with low intrinsic costs could decrease the total investment required to reach break-even by up to 70 billion USD, as compared to a scenario where x-Si continues to dominate the market. Furthermore, the system component analysis indicates that existing TF modules can reach the low cost levels assumed in the experience curve model. These results suggest that the future growth of photovoltaics (PV) is dependent on which PV technologies grow most rapidly. New, low intrinsic cost technologies that are successfully able to enter the market could dramatically increase the potential for PV to become a globally significant energy conversion technology within the next two decades.
Venue	Trancik and Zweibel, WCPEC-4 2006
Sources	National Renewable Energy Laboratory; Santa Fe Institute
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	05/2006

Post Date	09/19/2006
Title	CSG-1: MANUFACTURING A NEW POLYCRYSTALLINE SILICON PV TECHNOLOGY
Link	(PDF 378 KB) Download Acrobat Reader.
Author	P. A. Basore
Description	Crystalline Silicon on Glass (CSG) is a polycrystalline silicon PV (photovoltaic) technology that requires less than two micrometers of silicon thickness. At the time of this writing in April 2006, production of CSG solar panels is just beginning in a full-scale factory known as CSG-1. It was only 14 months ago, in February 2005, that groundbreaking for this factory occurred. At that time, the technology had only been demonstrated in 900-cm laboratory samples. This article discusses some of the challenges faced in taking a new PV technology from R&D into production in such a short period of time. Photos of the equipment used for each of the key steps are shown and the experience of commissioning the process is discussed.
Venue	Presented at the 4th World Conference on Photovoltaic Energy Conversion, Waikoloa, Hawaii, 9 May 2006
Source	CSG Solar
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	05/2006

Post Date	06/02/2006
Title	ULTRA-LIGHT AMORPHOUS SILICON CELL FOR SPACE APPLICATIONS
Link	(PDF 140 KB) Download Acrobat Reader.
Author	N. Wyrsch
Description	For space applications, solar cells should be optimized for highest power density rather than for highest efficiency. In this context, relatively low efficiency thin-film solar cell may well surpass multi-junction III-V based solar cells if they can be made thin enough. In thin-film solar cells the power density is mostly limited by the substrate. The introduction of ultra-thin polymeric substrates is the key for decreasing the cell mass. In this work, a very thin polyimide film LaRC?-CP1 was used as substrate or superstrate for amorphous silicon solar cell fabrication. CP1 films were either fixed on a glass carrier or spin coated onto a glass carrier coated with a release agent. By depositing amorphous silicon cells on 6 µm thick CP1 films, a power density of 2.9 W/g under AM1.5g and of 3.9 W/g (estimated) under AM0 illumination spectra was achieved, in substrate (n-i-p) configuration (for a cell area of ca. 0.25 cm2).
Venue	4th WCPEC May 2006
Source	University of Neuchatel
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	05/2006

Post Date	12/23/2005
Title	PATHWAYS TO THIN FILM POLYCRYSTALLINE SILICON USING AMORPHOUS SILICON PRECURSORS
Link	(MS Word 482 KB)
Authors	O. Ebil, S. S. Hegedus, R. W. Birkmire
Description	Multiple pathways to producing large grain Si films on low cost substrates have been investigated. A-Si films deposited by Hot Wire CVD (HWCVD) on glass have been crystallized by in-situ Aluminum-induced crystallization (AIC). The AIC occurs during the a-Si growth at 430°C eliminating the need for a separate AIC step. Both the Si/Al thickness ratio and Si thickness are critical to give optimum poly-Si films. Maximum a-Si and Al thicknesses of 0.6 and 0.5 µm resulted in continuous films with grains ~10 µm.
Venue	Solar Technology Review Meeting, Denver, CO, 11/7-10/2005
Source	University of Delaware
Document Type	Conference Papers (Word document)
Resource Date	11/2005

Post Date	10/20/2005
Title	FABRICATION AND CHARACTERIZATION OF TRIPLE-JUNCTION AMORPHOUS SILICON BASED SOLAR CELL WITH NANOCRYSTALLINE SILICON BOTTOM CELL
Link	(PDF 147 KB) Download Acrobat Reader.
Authors	X. Deng, et al.
Description	Highlights of recent research activities and results on the project ?The Fabrication and Characterization of High-efficiency Triple-junction a-Si Based Solar Cells? at the University of Toledo (UT) under the NREL TFPP Program are briefly reviewed in this paper. Using VHF PECVD, new growth regimes have been established at UT for preparation of high quality a-Si, a-SiGe and nc-Si i-layers at rates of 2-15 Å/s. Initial efficiencies of 7.2%, for VHF nc-Si n-i-p single-junction solar cells, 9.6% for a-Si/nc-Si tandem cells, and 11.0% for a-Si/a- SiGe/nc-Si triple cells have all been achieved. The progress of our research on high-rate nc-Si deposition using high pressure (8 Torr) PECVD is also reported.
Venue	DOE Solar Program Review 2005, Denver
Source	University of Toledo
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	10/2005

Post Date	10/20/2005
Title	A REVIEW OF RISKS IN THE SOLAR ELECTRIC LIFE-CYCLE
Link	(PDF 642 KB) Download Acrobat Reader.
Authors	V. Fthenakis, H. C. Kim
Description	Early studies of risks in the life cycle of solar electric technologies do not represent their current stage of development. Our study updates the data used in previous studies and also accounts for the full life-cycle of photovoltaics. We show that the non-radiological risks of the solar electric- and nuclear-life cycles are approximately equal. This contradicts the conclusions of some earlier studies according to which the former presented much greater occupational and public non-radiological risks than the latter.
Venue	Brussels 2005
Source	Brookhaven National Laboratory
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	10/2005

Post Date	09/13/2005
Title	AMORPHOUS SILICON- FROM DOPING TO MULTI-BILLION DOLLAR APPLICATIONS.
Link	(PDF 342 KB) Download Acrobat Reader.
Author	A. Madan
Description	In this paper, we recount the history leading up to the landmark paper by Spear and LeComber in 1975, which showed, contrary to thought at the time, that it was indeed possible to incorporate substitutionally pentavalent and trivalent impurities into a tetrahedral amorphous semiconductor. This work provided the basis for a multi-billion dollar business with products which are ubiquitous.
Venue	Invited talk: presented at ICANS21, Lisbon, Portugal, Sept. 2005
Source	MVSystems
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	09/2005

Post Date	07/26/2005
Title	DEVICE PERFORMANCES AND SIMULATIONS FOR SEVERAL KINDS OF LARGE-SCALE THIN FILM SILICON SOLAR CELL MODULES -INTRODUCTION OF SUPER SEE-THROUGH THIN FILM SOLAR CELL MODULE AND APPLICATIONS
Link	(PDF 219 KB) Download Acrobat Reader.
Author	Kishimoto
Description	We fabricated large-scale thin film silicon solar cell modules with amorphous silicon and micro-crystallized p-i-n structure on a TCO film by a PECVD system. We also developed the device simulator for conventional and see-through thin film solar cell modules, and simulated their cell performances in order to estimate the influences of some electrical factors such as a series resistance, a shunt pass and its distribution. We confirmed the initial conversion efficiency of 12.1%(Pm 58.4W, Im 1.22A, Voc 67.4V, F.F. 0.711), corresponding to about 11% stabilized conversion efficiency and the initial conversion efficiency of 10.0%(Pm 48.1W, Im 1.05A, Voc 66.4V, F.F. 0.717) of a super see-through thin film solar module with 10% transparency with the same substrate size of 560x925mm.
Venue	Barcelona, PVSC
Source	Sharp
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	06/2005

Post Date	06/13/2005
Title	IMPLICATIONS OF EUROPEAN ENVIRONMENTAL LEGISLATION FOR PHOTOVOLTAIC SYSTEMS
Link	(PDF 434 KB) Download Acrobat Reader.
Authors	M. J. De Wild-Scholten, K. Wambach, E. A. Alsema, A. Jager-Waldau
Description	An overview is given of European environmental legislation which is effective now or proposed and which may have implications for the photovoltaic industry. The focus will be on legislation, which has been implemented already in national law, like the WEEE (waste electrical and electronic equipment)- and ROHS Reach (Registration, Evaluation, Authorisation and Restriction of Chemicals), F-gases (regulation on certain fluorinated greenhouse gases) and EuP (eco-design requirements for energy-using products). A change of the module design, with the research, development, implementation and certification necessary to be able to produce photovoltaic systems that comply with such legislation, may be very time-consuming and expensive. Therefore a pro-active approach by the PV community is desirable. Environmental life cycle thinking and eco-design is becoming increasingly important as part of the European product and waste policy and will have its impact on the PV industry as well. Design-for-recycling must be encouraged to allow for an easy, cost-effective disassembly, with a high retrieval of for instance the precious crystalline silicon solar cells. A closed production cycle, i.e. guaranteed take back system, would probably prevent the commission as well as member states to impose legislative measures.
Venue	20th European PVSC Barcelona
Sources	Deutsche Solar; Energy Research Centre of the Netherlands
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	06/2005

Post Date	06/29/2005
Title	NREL PAPERS FOR THE PVSC IN ORLANDO, 2005
Link	(MS Word 41 KB)
Author	N/A
Description	Links to about 20 papers in CIS, CdTe, a-Si, thin Si and reliability.
Venue
Source	National Renewable Energy Laboratory
Document Type	Conference Papers (Word document)
Resource Date	06/2005

Post Date	05/09/2005
Title	TEMPERATURE-DEPENDENT OPEN-CIRCUIT VOLTAGE MEASUREMENTS AND LIGHT-SOAKING INHYDROGENATED AMORPHOUS SILCON SOLAR CELLS
Link	(MS Word 334 KB)
Authors	S. Guha, J. Liang, E. A. Schiff, B. Yan, J. Yang
Description	We present temperature-dependent measurements of the open-circuit voltage VOC(T) in hydrogenated amorphous silicon pin solar cells prepared at United Solar. At room-temperature and above, VOC measured using near-solar illumination intensity differs by as much as 0.04 V for the as-deposited and light-soaked states; the values of VOC for the two states converge below 250 K. Models for VOC based entirely on recombination through deep levels (dangling bonds) do not account for the convergence effect. The convergence is present in a model that assumes the recombination traffic in the as-deposited state involves only bandtails, but which splits the recombination traffic fairly evenly between bandtails and defects for the light-soaked state at room-temperature. Recombination mechanisms are important in understanding light-soaking, and the present results are inconsistent with models that assume an immediate connection between a recombination process and defect generation.
Venue	MRS Spring Meeting 2005, San Francisco, CA, Symposium A
Sources	Syracuse University; Uni-Solar Ovonic
Document Type	Conference Papers (Word document)
Resource Date	04/2005

Post Date	05/09/2005
Title	LIGHT-SOAKING EFFECTS ON THE OPEN-CIRCUIT VOLTAGE OF A-SI:H SOLAR CELLS
Link	(MS Word 938 KB)
Authors	S. Guha, J. Liang, E. A. Schiff, B. Yan, J. Yang
Description	We present measurements on the decline of the open-circuit voltage VOC in a-Si:H solar cells during extended illumination (light-soaking). We used a near-infrared laser that was nearly uniformly absorbed in the intrinsic layer of the cell. At the highest photogeneration rate (about 2x1021 cm-3), a noticeable decline (0.01 V) occurred within about 10 minutes; VOC stabilized at 0.04 V below its initial value after about 200 hours. We found that both the kinetics and the magnitudes of VOC are reasonably consistent with the predictions of a calculation combining a bandtail+defect picture for recombination and a hydrogen-collision model for defect generation. The version of the hydrogen-collision model that we used assumes that only bandtail recombination drives the hydrogen collision processes. Within this picture, the crossover between bandtail and defect recombination occurs on the same timescale as the ?light-induced annealing? process that accounts for stabilization of the optoelectronic properties for long light-soaking times.
Venue	MRS 2005 Spring Meeting, San Francisco, CA, Symposium A
Sources	Syracuse University; Uni-Solar Ovonic
Document Type	Conference Papers (Word document)
Resource Date	04/2005

Post Date	02/07/2005
Title	THE ROLE OF POLYCRYSTALLIN THIN-FILM PV TECHNOLOGIES FOR ACHIEVING MID-TERM MARKET-COMPETITIVE PV MODULES
Link	(MS Word 123 KB)
Authors	B. Von Roedern, K. Zweibel
Description	Using efficiency as the main parameter, projecting the cost competitiveness of thin films and x-Si. Current commercial status of CuInSe₂ alloys (collectively, CIS) and CdTe-based photovoltaic (PV) modules, comparing the performance of commercial products with the results achieved for solar cell and prototype module champions. We provide an update for these PV cell and module technologies, and also compare CIS and CdTe performance levels to the results achieved by the crystalline Si PV industry. This comparison shows that CIS and CdTe module technology presently offers the best (and perhaps only) approach for significantly exceeding the cost/performance levels established by crystalline Si PV technologies. A semi-empirical methodology is used for comparing "champion" solar cell and prototype module data with performance achieved on manufacturing lines. Using a conservative assumption that thin-film technologies will eliminate the 40% of PV module costs arising from the Si wafer or ribbon, we estimate the future performance of all established PV module candidates, and conclude that, based on 2004 knowledge about each PV technology, CIS and CdTe should provide cost-competitive advantages over crystalline Si.
Venue	IEEE PV Specialists Conference, 2004
Source	National Renewable Energy Laboratory
Document Type	Conference Papers (Word document)
Resource Date	01/2005

Post Date	02/15/2005
Title	ANALYTICAL RESULTS OF OUTPUT RESTRICTION DUE TO THE VOLTAGE INCREASING OF POWER DISTRIBUTION LINE IN GRID-CONNECTED CLUSTERED PV SYSTEMS
Link	(PDF 2.4 MB) Download Acrobat Reader.
Authors	Y. Ueda, et al.
Description	Output restriction to prevent over voltage of power distribution line is one of the concerns for grid-connected clustered PV systems. To investigate the behavior of clustered PV systems, "Demonstrative research on clustered PV systems" has being conducted from December, 2002 in Gunma, Japan. More than 200 residential PV systems are already installed in demonstrative research area. Operation point of array output is estimated using minutely averages of collected data. The method to quantify loss due to output restriction is developed in this study.
Venue	IEEE PVSC
Source	Tokyo University
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	01/2005

Post Date	02/11/2005
Title	LIFE CYCLE ASSESSMENT OF PHOTOVOLTAICS: PERCEPTIONS, NEEDS, AND CHALLENGES
Link	(PDF 222 KB) Download Acrobat Reader.
Authors	E. A. Alsema, M. J. De Wild-Scholten, V. Fthenakis
Description	High impact publications recently depicted PV technologies as having higher external environmental costs than those of nuclear energy and natural-gas-fueled power plants. These assessments are based on old data and unbalanced assumptions, and they illustrate the need for LCA data describing the continuously improving photovoltaic systems and the inclusion of social benefits in this comparison.
Venue	IEEE Photovoltaic Specialistis Conference, Jan. 3-7, 2005, Orlando, FL
Sources	Brookhaven National Laboratory; Energy Research Centre of the Netherlands; Utrecht University
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	01/2005

Post Date	02/15/2005
Title	EARLY PERFORMANCE FOR THE ROOF-MOUNTED, 20-KW THIN FILM CDTE PV-ARRAY AT JASPER RIDGE
Link	(PDF 364 KB) Download Acrobat Reader.
Authors	J. H. Scofield, et al.
Description	Here we report early performance for the grid-connected, 20-kW CdTe PV array installed on the roof of the Leslie Shao-ming Sun Field Station at the Jasper Ridge Biological Preserve. The array was installed in May 2002. Data are reported for 20-mos beginning April 2003. The array originally consisted of 275, BP Solar 80W thin-film CdTe modules arranged in 11-module strings. The monitoring system logged data from 9 sensors on 1-min intervals. Monitoring showed problems with maximum power tracking associated with module degradation, ele-vated module temperatures, and the finite voltage window of the 208VAC-3p inverter. The problems were addressed in May 2004 by re-wiring the array and reprogramming the inverter, resulting in a 20% increase in energy production.
Venue	IEEE PVSC
Source	Oberlin College
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	01/2005

Post Date	02/09/2005
Title	PHYSICAL MODES OF THIN-FILM PV DEGRADATION
Link	(PDF 267 KB) Download Acrobat Reader.
Authors	V. G. Karpov, et al.
Description	We discuss physical modes of degradation related to the small thickness and lack of crystallinity in thin-film PV. We discriminate between 1) uniform material degradation through defect generation, light-induced diffusion, and electro-migration; 2) nonuniform degradation through ohmic or non-ohmic shunts; 3) metal contact deterioration. The first can equally apply to bulk and thin-film PV. Two others are specific to thin-film PV.
Venue	IEEE
Source	University of Toledo
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	10/2004

Post Date	02/04/2005
Title	STUDY OF POTENTIAL COST REDUCTIONS RESULTING FROM SUPER-LARGE-SCALE MANUFACTURING OF PV MODULES
Link	(MS Word 112 KB)
Authors	R. Arya, M. Keshner
Description	Short version of multi-GW production report
Venue	NREL Solar Review
Source	Hewlett Packard
Document Type	Conference Papers (Word document)
Resource Date	10/2004

Post Date	02/07/2005
Title	TECHNOLOGY AND MARKET CHALLENGES TO MAINSTREAM THIN-FILM PHOTOVOLTAIC MODULES AND APPLICATIONS
Link	(PDF 276 KB) Download Acrobat Reader.
Author	R. Arya
Description	Technology and manufacturing advances over the past 25 years has led to widespread commercial use of thin film modules in many consumer applications. The three leading thin film solar module technologies are - amorphous silicon alloys (a-Si), copper indium diselenide alloys (CIGS), and cadmium telluride CdTe). These three technologies have demonstrated solar cells with efficiencies ~13% (a-Si), ~19% (CIGS), and ~16.5% (CdTe) respectively. Large area power modules are in various stages of initial production with these technologies and the module performance is in the 6%-11% range. Several manufacturing plants are in operation with plant capacities ranging from 3 MW to 30 MW. These plants are continuously increasing production with the present annual production of 1 MW to 5 MW. Technical challenges lie ahead in improving the module performance by reducing the gap between R&D cells and manufactured products so that they can successfully compete with crystalline silicon modules. Reliability of thin film modules in systems has been demonstrated with all three technologies with a fair degree of success. Several 1-480 kW grid-connected thin film module arrays are in deployment worldwide. Thin film modules are finding increasing acceptance for BIPV applications like roofs, facades, awnings etc. used in residential and commercial buildings. The cost of modules and market acceptance with new technologies still remains a major challenge to successful penetration of mainstream photovoltaic markets.
Venue
Source	N/A
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	2004

Post Date	05/10/2005
Title	NEW R&D TRENDS IN EUROPE ON THIN-SILICON PHOTOVOLTAICS
Link	(PDF 159 KB) Download Acrobat Reader.
Authors	F. Roca, et al.
Description	About 99% of the solar-cell world production for PV terrestrial applications is dominated by silicon, of whose share, about 80% corresponds to wafer technology. Experience has induced the conviction that silicon technology must keep this predominant position for the next 10 years. Progress in wafer technology is needed in the direction of increasing production and lowering costs of feedstock, mainly by investigating new growth processes leading to a cheaper silicon of an acceptable quality. The development of medium-thickness polycrystalline ribbon silicon and similar silicon-based materials is in the forefront of photovoltaic R&D. In parallel, the efforts on thin-film silicon technology must be concentrated on enhancing material quality by improving film crystallinity and simultaneously thickness and growth rate. New approaches for the preparation of silicon impose a convergence of two research lines traditionally separated. The European state of the art in thin silicon for PV is analysed and described. A successful European RTD strategy imposes the collaboration of public and private institutions both within the present Framework Programme, FP5, and even more in the coming FP6, by means of Networks of Excellence (NoE) and Integrated projects (IP) in order to create the so called European Research Area.
Venue
Source	ENEA
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	2004

Post Date	02/08/2005
Title	SI:H MATERIALS AND SOLAR CELLS RESEARCH AT PENN STATE
Link	(PDF 3.2 MB) Download Acrobat Reader.
Authors	C. Wronski, et al.
Description	Progress in Research on Si:H Materials and Solar Cells Research at Penn State.
Venue	DOE Photovoltaics Subprogram Peer Review August 13-15, 2003
Source	Pennsylvania State University
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	08/13/2003

Post Date	03/15/2005
Title	OVERVIEW OF AMORPHOUS SILICON (A-SI) PHOTOVOLTAIC INSTALLATIONS AT SMUD
Link	(PDF 519 KB) Download Acrobat Reader.
Author	D. E. Osborn
Description	The Sacramento Municipal Utility District (SMUD) Solar Program has installed over 10 MW of photovoltaic (PV) systems including more than 2,000 kW of amorphous silicon (a-Si), thin film PV systems installed since 1994 in systems ranging from 1 kW to 700 kW. While lower in efficiency compared to the more traditional single-crystal silicon (c-Si) and polycrystalline silicon (pc-Si) PV modules, the significantly lower price per Watt of a-Si can often result in dramatic turnkey system savings despite increased area-related installation costs. arrays at PV power stations.
Venue	ASES Solar 2003 * June 2003 * Austin, TX
Source	Spectrum Energy Corp
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	06/2003

Post Date	03/15/2005
Title	LARGE-AREA DEPOSITION FOR CRYSTALLINE SILICON ON GLASS MODULES
Link	(PDF 476 KB) Download Acrobat Reader.
Author	P. A. Basore
Description	This paper presents the current status of the Crystalline Silicon on Glass (CSG) technology for lowcost photovoltaic modules that is being developed at Pacific Solar. This technology combines the low manufacturing cost of large-area monolithic construction with the established durability of crystalline silicon. The heart of the manufacturing sequence for this technology is the PECVD silicon deposition process. Equipment developed for the flat-panel display industry appears to meet the requirements for this process. A single-chamber KAI-800 system from Unaxis has been installed at Pacific Solar that deposits silicon layers onto 0.7-m2 ...
Venue	IEEE
Source	Pacific Solar Pty Ltd
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	05/16/2003

Post Date	02/09/2005
Title	THE MESOSCALE PHYSICS OF LARGE-AREA PHOTOVOLTAICS
Link	(PDF 252 KB) Download Acrobat Reader.
Authors	V. G. Karpov, et al.
Description	Recent findings make the physics of large-area thin-film devices a distinctive field of its own, considerably different from that of microelectronics. We show that (i) large-area thin-film photovoltaic (PV) devices are intrinsically nonuniform in the lateral directions, (ii) the nonuniformity spans over microscopically large dimensions, which can vary dramatically (from microns to meters) depending on light intensity and bias, and (iii) the nonuniformity significantly impacts the device performance and stability. Our understanding suggests the concept of interfacial layer that blocks the nonuniformity effects and can be applied photo-electrochemically. This concept is experimentally verified.
Venue	29th IEEE Osaka
Source	University of Toledo
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	05/16/2003

Post Date	02/07/2005
Title	PRACTICAL DOPING PRINCIPLES
Link	(PDF 270 KB) Download Acrobat Reader.
Author	A. Zunger
Description	Doping compound semiconductors.
Venue	NREL DOE Solar Program Review Meeting 2003
Source	National Renewable Energy Laboratory
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	2003

Post Date	03/15/2005
Title	PROPERTIES OF SI:H MIXED AMORPHOUS MICROCRYSTALLINE PHASES
Link	(PDF 342 KB) Download Acrobat Reader.
Authors	R. W. Collins, C. Wronski
Description	at The Pennsylvania State University have shown that the thin film Si:H prepared under moderate-to-high H2-dilution conditions with low temperature rf plasma enhanced chemical vapor deposition (PECVD) evolves from the amorphous phase to a mixed amorphous + microcrystalline phase [(a+µc)-Si:H] with the accumulated thickness of the layer. The thin film material in the amorphous regime of growth has been called "protocrystalline" Si:H and exhibits a higher degree of ordering than materials deposited under similar conditions without H2-dilution [1-3]. Furthermore they showed that the phase evolution of this material with thickness and, in particular, the transition to the mixed-phase (a+µc)-Si:H material, depends not only on hydrogen dilution ratios, R=[H2]/[SiH4], but also on the substrate material. Consequently, without using real time spectroscopic ellipsometry (RTSE) or equally powerful techniques, it is not possible to control the growth of the protocrystalline Si:H materials and cell structures or to characterize their properties reliably. The insights into the growth process and microstructural evolution into the (a+µ
Venue	NREL National Team meeting
Source	Pennsylvania State University
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	2003

Post Date	03/25/2005
Title	OPTIMIZATION OF PHASE-ENGINEERED A-SI:H-BASED MULTIJUNCTION SOLAR CELLS
Link	(PDF 397 KB) Download Acrobat Reader.
Authors	C. Wronski, et al.
Description	A comprehensive understanding is being developed on the subjects of Si:H material deposition as well as device limiting mechanisms. First, it has been demonstrated that the protocrystalline nature of the p-layers and not their microcrystalline nature is responsible for obtaining high VOC and also that VOC can be maximized through the deposition procedure. Second, recombination at p/i interfaces has been identified and quantified on cells with different i-layers and a-Si:H p-i interface layers. The bulk recombination in both the JD-V and JSC-VOC characteristics,which exhibit superposition, is found to be consistent with the Shockley-Reed-Hall model, and the observed spatially uniform distributions of defects in the i-layers are contrary to the predictions of the defect pool model. Third, results obtained on sub-bandgap absorption spectra
Venue	NCPV and Solar Program Review Meeting 2003 NREL/CD-520-33586 Page 789
Source	Pennsylvania State University
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	2003

Post Date	02/02/2005
Title	COMPARISON OF ENERGY PRODUCTION AND PERFORMANCE FROM FLAT-PLATE PHOTOVOLTAIC MODULE TECHNOLOGIES DEPLOYED AT FIXED TILT
Link	(PDF 206 KB) Download Acrobat Reader.
Author	J. A. del Cueto
Description	energy rating by technology
Venue
Source	National Renewable Energy Laboratory
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	2003

Post Date	02/08/2005
Title	STATUS OF AMORPHOUS AND CRYSTALLINE THIN-FILM SILICON SOLAR CELL ACTIVITIES
Link	(PDF 223 KB) Download Acrobat Reader.
Author	B. Von Roedern
Description	This paper reviews the recent activities and accomplishments of the national Amorphous Silicon Team and a (crystalline) thin-film-Si subteam that was implemented in 2002 to research solar cell devices based on thin-crystalline-Si-based layers. This paper reports the evolution of team organization, technical highlights from recent team meetings, and an outlook on commercialization potential.
Venue	NCPV and Solar Program Review Meeting 2003
Source	National Renewable Energy Laboratory
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	2003

Post Date	02/07/2005
Title	PROGRESS IN U.S. PHOTOVOLTAICS: LOOKING BACK 30 YEARS AND LOOKING AHEAD 20
Link	(PDF 310 KB) Download Acrobat Reader.
Author	T. Surek
Description	Technology and learning curve analysis of R&D.
Venue	Osaka IEEE
Source	National Renewable Energy Laboratory
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	2003

Post Date	03/15/2005
Title	STATUS OF HYDROGENATED MICROCRYSTALLINE SILICON SOLAR CELLS AT UNITED SOLAR
Link	(PDF 244 KB) Download Acrobat Reader.
Authors	J. Yang, et al.
Description	We have studied the performance of hydrogenated microcrystalline silicon (µc-Si:H) solar cells using three different deposition techniques. Deposition rates ranging from low (~1Å/s), to medium (~3-10 Å/s), to high (~20 - 30 Å/s) have been obtained by using conventional radio frequency (RF), modified very high frequency (MVHF), and microwave (µ-wave) excitations, respectively; initial activearea efficiencies of 7.4%, 7.1%, and 4.9% have been achieved for the respective techniques in a single-junction structure. Double-junction cells using a-Si:H in the top and µc-Si:H in the bottom have yielded initial active-area efficiencies of 13% and 12.3% for RF and MVHF techniques, respectively. Stability and other issues will be reported.
Venue	NCPV and Solar Program Review Meeting 2003 NREL/CD-520-33586 Page 556
Source	Uni-Solar Ovonic
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	2003

Post Date	02/09/2005
Title	MICRONONUNIFORMITY EFFECTS IN THIN-FILM PHOTOVOLTAICS
Link	(PDF 350 KB) Download Acrobat Reader.
Authors	A. Compaan, V. G. Karpov, D. Shvydka
Description	We discuss effects of micrononuniformities on thin-film photovoltaics. The key factors are the device large area and the presence of potential barriers. We model the nonuniformity effects in the terms of random microdiodes connected in parallel through a resistive electrode. The microdiodes of low open circuit voltages affect macroscopically large regions. They strongly reduce the device performance and induce its nonuniform degradation in several different modes. We support our predictions by experiments.
Venue	2002 IEEE PVSC
Source	University of Toledo
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	2002

Post Date	02/08/2005
Title	MODEL FOR STAEBLER-WRONSKI DEGRADATION DEDUCED FROM LONG-TERM, CONTROLLED LIGHT-SOAKING EXPERIMENTS
Link	(PDF 227 KB) Download Acrobat Reader.
Authors	B. Von Roedern, J. A. del Cueto
Description	Long-term light-soaking experiments of amorphous silicon photovoltaic modules have now established that stabilization of the degradation occurs at levels that depend significantly on the operating conditions, as well as on the operating history of the modules. We suggest that stabilization occurs because of the introduction of degradation mechanisms with different time constants and annealing activation energies, depending on the exposure conditions. Stabilization will occur once a sufficient accumulation of different degradation mechanisms occurs. We find that operating module temperature during light-soaking is the most important parameter for determining stabilized performance. Next in importance is the exposure history of the device. The precise value of the light intensity seems least important in determining the stabilized efficiency, as long as its level is a significant fraction of 1-sun.
Venue	MRS 2000
Source	National Renewable Energy Laboratory
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	2002

Post Date	03/15/2005
Title	SUPERIOR ENERGY YIELDS OF UNI-SOLAR® TRIPLE JUNCTION THIN FILM SILICON SOLAR CELLS COMPARED TO CRYSTALLINE SILICON SOLAR CELLS UNDER REAL OUTDOOR CONDITIONS IN WESTERN EUROPE
Link	(MS Word 747 KB)
Authors	et al., M. van Cleef
Description	For many years, amorphous silicon photovoltaic modules have had difficulties to establish themselves in the grid-connected PV-market. Causes for this lack of market acceptance of first generation amorphous silicon PV modules were their relatively low conversion efficiencies, unstable power and not well understood outdoor characteristics. Various manufacturers of amorphous silicon modules have resolved these initial problems by enhancing the efficiencies of their cells, while at the same time improving the long-term stability of the products. Still, the outdoor behaviour of amorphous silicon modules is not well understood by many users, even by insiders of the PV-community. Results of this study will show that new generation multi-junction amorphous silicon modules, and in particular UNI-SOLAR® modules based on the Triple Junction solar cells, perform excellent under western European climatic conditions, with yields and performance ratios significantly higher than all present crystalline silicon technologies. This effect is especially pronounced under low light conditions and under non-ideal orientations. The enhanced outdoor performance, up to 20 % higher on a yearly kWh/kWp base, can be attributed to the higher sensitivity for low light conditions and for diffuse light, better performance at high temperatures and improved shadow tolerance of UNI-SOLAR® modules.
Venue	17th EuroPV Solar Energy Conference, Munich
Source	Energy Conversion Devices
Document Type	Conference Papers (Word document)
Resource Date	10/2001

Post Date	02/07/2005
Title	PV SOLAR ELECTRICITY: ONE AMONG THE NEW MILLENNIUM INDUSTRIES
Link	(PDF 6.0 MB) Download Acrobat Reader.
Author	W. Hoffmann
Description	ABSTRACT: During recent years, solar electricity generation based on photovoltaics has developed into an industry at annual growth rates above 20%. Major market segments served by this industry comprise consumer applications, remote industrial systems, developing countries, and grid-connected systems. The potential in these markets supports sustained future growth, particularly for applications in developing countries and gridconnected systems in the industrial countries, where PV-generated electricity eventually will start to compete with peak grid power. Backed by price experience curves and a laboratory proven technology road map, a module turnover representing 100 billion worlwide can be extrapolated. A sustainable energy contribution to the worldwide energy mix in subsequent decades is foreseen as a result of competitive PV solar electricity applications. Keywords: PV Market Growth ? 1: Strategy ? 2: Cost Reduction ? 3
Venue	17th European Photovoltaic Solar Energy Conference, Munich, Germany, 22-26 October 2001
Source	RWE Schott
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	10/2001

Post Date	03/15/2005
Title	STABILITY AND NANOSTRUCURE OF HETEROGENEOUS AMORPHOUS SILICON THIN-FILM SYNTHESIZED UNDER HIGH CHAMBER PRESSURE (500 TO 2200 MTORR) REGIME OF RF PECVD
Link	(PDF 348 KB) Download Acrobat Reader.
Author	A. R. Middya
Description	We report on improvement in stability of a new type of amorphous silicon films, synthesized (growth rate > 0.1 nm/s) by driving the plasma condition close to the (or "?-regime") of rf PECVD. These films exhibit high mobility-lifetime products [(??)annld ? 10- 4 cm2/V, ?ph/?d ? 5-10x105, Ea ? 0.7 - 0.9 eV ], compact network structure [CH ? 7 to 8 at%, nanovoid density < 0.01 %, ? ? 2.23 ± 0.01 gm/cm3], new features of optical properties and density-of-state (DOS) above EF is significantly lower than that of state-of-the art films. The kinetics of light-induced (AM 1.5) degradation of ?? is very fast and saturated ?? ? 10-6 cm2/V, a value similar to that of conventional a-Si:H films at annealed state. The improved stability of "new" a-Si films, henceforth it will be denoted as "quasi-amorphous silicon (qm-Si) thinfilm", will be correlated with its specific nanostructure.
Venue	Mat. Res. Soc. Symp. Proc. Vol. 664
Source	Syracuse University
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	2001

Post Date	03/22/2005
Title	GUIDING PRINCIPLE TO DEVELOP INTRINSIC MICROCRYSTALLINE SILICON ABSORBER LAYER FOR SOLAR CELL BY HOT-WIRE CVD
Link	(PDF 250 KB) Download Acrobat Reader.
Authors	A. R. Middya, et al.
Description	We report on ways to develop device quality microcrystalline silicon (?c-Si:H) intrinsic layer with high growth rate by hot-wire chemical vapor deposition (HWCVD). With combine approach of controlling impurities and moderate H-dilution [H2/SiH4 ? 2.5], we developed, for the first time, highly photosensitive (103) ?c-Si:H films with high growth rate (>1 nm/s); the microstructure of the film is found to be close to amorphous phase (fc ? 46 ± 5%). The photosensitivity systematically decreases with fc and saturates to 10 for fc > 70%. On application of these materials in non-optimized pin ?c-Si:H solar cell structure yields 700 mV open-circuit voltage however, surprisingly low fill factor and short circuit current. The importance of reduction of oxygen impurities [O], adequate passivation of grain boundary (GB) as well as presence of inactive GB of (220) orientation to achieve efficient uc-Si:H solar cells are discussed.
Venue	Mat. Res. Soc. Symp. Proc. Vol. 664
Source	University of Kaiserslautern
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	2001

Post Date	02/11/2005
Title	HEALTH, SAFETY AND ENVIRONMENTAL ISSUES IN THIN FILM MANUFACTURING
Link	(PDF 50 KB) Download Acrobat Reader.
Authors	E. A. Alsema, et al.
Description	An investigation is made of Health, Safety and Environmental (HSE) aspects for the manufacturing, use and decommissioning of CdTe, CIS and a-Si modules. Issues regarding energy requirements, resource availability, emissions of toxic materials, occupational health and safety and module waste treatment are reviewed. Waste streams in thin film module manufacturing are analyzed in detail and treatment methods are discussed. Finally the technological options for thin film module recycling are investigated. It is concluded that there are no serious HSE bottlenecks for upscaling to production levels of 500 MWp/yr and that adequate methods are available for treatment of the manufacturing wastes. However, on the longer term issues regarding CdTe and CIS module waste treatment, In and Te resource availibility and module recycling need to adressed. Appropriate recycling methods for CdTe and CIS modules do not exist at present but the problem is being adressed by the PV industry.
Venue
Source	Utrecht University
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	2000

Presentations

Post Date	04/30/2007
Title	SI THIN-FILM PHOTOVOLTAICS PROGRAM IN THE U.S.
Link	(PDF 1.5 MB) Download Acrobat Reader.
Author	B. Von Roedern
Description	Presentation Outline: (1) History of U.S. a-Si (film-Si) program (2) Results of activities (3) Competing PV Technologies (4) Outlook
Venue	presented at International Workshop upon Thin Film Silicon Solar Cells, Nara, Japan, 2/28 - 3/2/2007
Source	National Renewable Energy Laboratory
Document Type	Presentation (Adobe Postscript file)
Resource Date	02/2007

Post Date	06/05/2006
Title	OPTICAL CHARACTERIZATION OF ZNO/AG STRUCTURES FOR APPLICATIONS AS BACK-REFLECTORS IN THIN FILM SI SOLAR CELLS
Link	(PowerPoint 3.2 MB)
Authors	R. W. Collins, N. Podraza, X. Deng
Description	Spectroscopic Ellipsometry was used to study various back-reflector formulations
Venue	R. Collins, University of Toledo, presentation, a-Si Team Meeting 04/17/2006
Source	University of Toledo
Document Type	Presentation (Powerpoint presentation)
Resource Date	04/17/2006

Post Date	06/06/2006
Title	STABILITY OF STAEBLER-WRONSKI DEFECTS AND THEIR INFLUENCE ON PHOTOCARRIER LIFETIME
Link	(PowerPoint 115 KB)
Author	P. Stradins
Description	1. Degradation of electron lifetime in coplanar structures strongly affected by thermal stability of light-induced defects. 2. Degradation of solar cells determined mostly by number of defects, not their stability 3. Weak acceptor effect accompanying defect creation is likely responsible for (1.) but weakly affects (2.) 4. Solar cell degradation could be minimized by determining and modifying atomic structures responsible for defect stability
Venue	P. Stradins, NREL, presentation a-Si Team Meeting 04/17/2006
Source	National Renewable Energy Laboratory
Document Type	Presentation (Powerpoint presentation)
Resource Date	04/17/2006

Post Date	06/05/2006
Title	PHASE DIAGRAM FOR SI(1-X)GE(X):H THIN FILMS
Link	(PowerPoint 19.1 MB)
Authors	R. W. Collins, N. Podraza, C. Wronski
Description	Hydrogen Dilution Phase Diagrams for a-SiGe:H, comparision to HE-dilution
Venue	N. Podzara and R. Collins, University of Toledo, presentation at the a-Si team meeting, 4/17/2006
Source	University of Toledo
Document Type	Presentation (Powerpoint presentation)
Resource Date	04/17/2006

Post Date	06/05/2006
Title	RECRYSTALLIZED LARGE-GRAIN SI FILMS
Link	(PowerPoint 16.2 MB)
Authors	M. Lu, O. Ebil, U. Das, S. S. Hegedus, R. W. Birkmire
Description	Analyses of Si films prepared by Al-induced recrystallization (exchange layer recrystallization)
Venue
Source	University of Delaware
Document Type	Presentation (Powerpoint presentation)
Resource Date	04/17/2006

Post Date	06/06/2006
Title	CORPORATE OVERVIEW
Link	(PowerPoint 3.4 MB)
Author	J. Yang
Description	Uni-Solar's Commercial Expansion and Company Overview
Venue	J. Yang, United Solar, presentation, a-Si Team Meeting 04/17/2006
Source	Uni-Solar Ovonic
Document Type	Presentation (Powerpoint presentation)
Resource Date	04/17/2006

Post Date	06/07/2006
Title	CHEMICAL ANNEALING FOR IMPROVED STABILITY
Link	(PowerPoint 245 KB)
Author	V. L. Dalal
Description	Discussion of the benefits of low-energy (<50 eV) ion bombardment on film properties
Venue	V. Dalal, Iowa State University, presentation, a-Si Team Meeting, 04/17/2006
Source	Iowa State University
Document Type	Presentation (Powerpoint presentation)
Resource Date	04/17/2006

Post Date	06/06/2006
Title	CORRELATION OF MATERIAL STRUCTURE AND LIGHT-INDUCED STABILITY IN NC-SI:H SOLAR CELLS
Link	(PowerPoint 923 KB)
Authors	G. Yue, G. Ganguly, J. Yang, S. Guha, C. Teplin, D. L. Williamson
Description	? We have improved the stability of nc-Si:H cells by optimizing the hydrogen dilution profiling ? Our previous results show that the light-induced defect generation are mainly in amorphous phase or grain boundary region ? However, the amorphous volume fraction is not the main factor for determining the degradation. The degradation is also related to the structure and distribution of the amorphous phase, as well as the properties of the grain boundaries ? Small grains or intermediate orders may play important roles. Further investigation is necessary
Venue	B. Yan, United Solar, presentation, a-Si Team Meeting, 04/17/2006
Sources	National Renewable Energy Laboratory; Uni-Solar Ovonic
Document Type	Presentation (Powerpoint presentation)
Resource Date	04/17/2006

Post Date	06/05/2006
Title	DEVICE PHYSICS OF NANOCRYSTALLINE (AND AMORPHOUS) SILICON SOLAR CELLS
Link	(PowerPoint 694 KB)
Author	E. A. Schiff
Description	Mobility/Band-Tail-Recombination modeling of Solar Cells
Venue	E. Schiff, Syracuse University, presentation a-Si Team Meeting 04/17/2006
Source	Syracuse University
Document Type	Presentation (Powerpoint presentation)
Resource Date	04/17/2006

Post Date	06/07/2006
Title	ELECTRONIC PROPERTIES IN NC-SI:H
Link	(PowerPoint 2.1 MB)
Author	V. L. Dalal
Description	Space-Charge-Limited Current measurements were used to deduce the following for nc-Si: 1. All the measurements indicate crystalline type behavior with much smaller carrier mobilities ? diffusion controlled device 2. Graded doping increases effective diffusion length significantly- indicates that ppm doping does not destroy the material 3. Both electron and hole mobilities measured using variety of techniques, both in vertical and horizontal (channel) direction 4. Mobility values are a few cm2/V-s
Venue	V. Dalal, Iowa Stae University, presentation, a-Si Team Meeting 04/17/2006
Source	Iowa State University
Document Type	Presentation (Powerpoint presentation)
Resource Date	04/17/2006

Post Date	06/05/2006
Title	HIGH EFFICIENCY, HIGH RATE FABRICATION OF A-SI, A-SIGE, NC-SI BASED SOLAR CELLS
Link	(PowerPoint 848 KB)
Author	A. Vijh
Description	When considering deposition rates and method, new record efficiencies were achieved at the university of Toledo. Cell analyses methods were developed by Midwest Optoelectronics
Venue
Sources	Midwest Optoelectronics LLC; University of Toledo
Document Type	Presentation (Powerpoint presentation)
Resource Date	04/17/2006

Post Date	06/06/2006
Title	IMPROVEMENT OF MULTI-JUNCTION SOLAR CELLS WITH NC-SI:H MIDDLE AND BOTTOM CELL
Link	(PowerPoint 2.1 MB)
Authors	B. Yan, G. Yue, G. Ganguly, J. Yang, S. Guha
Description	? 8.99% initial and 8.50% stable active-area efficiency for a nc-Si:H single-junction cell made with MVHF at 5-8 Å/s ? 15.1% initial active-area efficiency for an a-Si:H/a-SiGe:H/nc-Si:H triple-junction structure, where the top and the middle cells were made with RF at a low rate, the bottom cell with MVHF at a high rate ? 14.1% initial and 13.2% stable active-area efficiency for an a-Si:H/nc-Si:H/nc-Si:H triple-junction structure, where the top were made with RF at a low rate, the middle and bottom cell with MVHF at a high rate ? 9.5% stable aperture-area (420 cm2) efficiency for an encapsulated a-Si:H/nc-Si:H double-junction structure.
Venue	B. Yan, United Solar, presentation, a-Si Team Meeting, 04/17/2006
Source	Uni-Solar Ovonic
Document Type	Presentation (Powerpoint presentation)
Resource Date	04/17/2006

Post Date	06/05/2006
Title	PIER RENEWABLES SOLAR RD&D POLICY DRIVERS, CURRENT ACTIVITIES, AND FUTURE PLANS
Link	(PowerPoint 11.7 MB)
Authors	G. Kibrya, H. Mohammed
Description
Venue	G. Kibrya and H. Mohammed, PIER (CA Public Interest Energy Research Program), presentation, a-Si Team Meeting, 04/17/2006
Source	PIER CA Energy Commission (Public Interest Energy Research Program)
Document Type	Presentation (Powerpoint presentation)
Resource Date	04/17/2006

Post Date	06/05/2006
Title	INNOVATIVE CHARACTERIZATION OF AMORPHOUS AND THIN-FILM SILICON FOR IMPROVED MODULE PERFORMANCE
Link	(PowerPoint 3.2 MB)
Author	J. D. Cohen
Description	Defect spectra for NREL HW a-SiGe:H, influence of oxygen, defect spectra for nc-Si:H
Venue	D. Cohen, University of Oregon, presentation, a-Si Team Meeting 4/17/2006
Source	University of Oregon
Document Type	Presentation (Powerpoint presentation)
Resource Date	04/17/2006

Post Date	06/06/2006
Title	MEASUREMENT OF COMPONENT CELL IV CHARACTERISTICS IN MULTIJUNCTION SOLAR CELLS
Link	(PowerPoint 363 KB)
Authors	A. Vijh, X. Deng
Description
Venue	A. Vijh, Midwest Optoelectronics, presentation, a-Si Team Meeting 04/17/2006
Sources	Midwest Optoelectronics LLC; University of Toledo
Document Type	Presentation (Powerpoint presentation)
Resource Date	04/17/2006

Post Date	06/05/2006
Title	TA-FILAMENT HWCVD A-SIGE:H UPDATE
Link	(PowerPoint 2.1 MB)
Authors	H. M. Branz, A. H. Mahan, Y. Xu, R. C. Reedy
Description
Venue	H. Branz, NREL, a-Si team meeting presentation, 4/17/2006
Source	National Renewable Energy Laboratory
Document Type	Presentation (Powerpoint presentation)
Resource Date	04/17/2006

Post Date	06/06/2006
Title	CONDUCTIVE AFM MEASUREMENTS ON HYDROGENATED AMORPHOUS/NANOCRYSTALLINE MIXED-PHASE SOLAR CELLS
Link	(PowerPoint 5.9 MB)
Authors	B. Yan, S. Guha, C. Teplin, H. Moutinho, M. M. Al-Jassim
Description	1. We have used C-AFM to measure the local current mapping in the solar cells showing amorphous, mixed-phase, and nanocrystalline characteristics. 2. High current spikes were observed in the nanocrystalline areas. 3. The density of the current-spikes increases with the increase of crystalline phase. 4. A fully a-Si:H thick i/p buffer layer significantly reduced the magnitude of the current spikes. 5. Comparing the C-AFM images with the surface morphology, we believe that the areas with high current spikes are aggregations of small nanocrystallites. 6. These clusters of nanocrystallites with size of ~500 nm can form microscopic diodes. 7. These results provide additional evidence for the parallel-connected two-diode model for the mixed-phase solar cell and explain the observed dramatic drop of Voc at very low nanocrystalline volume fraction.
Venue	B. Yan, Uni-Solar, presentation, a-Si Team Meeting 04/17/2006
Sources	National Renewable Energy Laboratory; Uni-Solar Ovonic
Document Type	Presentation (Powerpoint presentation)
Resource Date	04/17/2006

Post Date	06/06/2006
Title	SPATIALLY RESOLVED RAMAN SPECTROSCOPY FOR A-SI:H & NC-SI STUDIES
Link	(PowerPoint 580 KB)
Author	C. W. Teplin
Description	Micro-Raman Studies using different wavelength (penetration depths)
Venue	C. Teplin, NREL, presentation, a-Si Team Meeting 04/17/2006
Source	National Renewable Energy Laboratory
Document Type	Presentation (Powerpoint presentation)
Resource Date	04/17/2006

Post Date	06/05/2006
Title	UPDATE ON METASTABILITY
Link	(PowerPoint 46 KB)
Author	R. Biswas
Description	Dangling-bond creation/annihilation
Venue	R. Biswas, Iowa State U. A-Si Team Meeting Presentation 4/17/2006
Source	Iowa State University
Document Type	Presentation (Powerpoint presentation)
Resource Date	04/17/2006

Post Date	06/06/2006
Title	NEW INSIGHTS INTO THE ROLE OF HYDROGEN IN THE STAEBLER-WRONSKI EFFECT IN A-SI:H
Link	(PowerPoint 1.1 MB)
Author	P. C. Taylor
Description	? More Silicon Dihydride Sites in ?Device Quality? Films than Previously Assumed ? Relationship of Silicon Dihydride to Metastable H Doublet Sites Unclear ? Dangling Bond Creation in Tritiated a-Si:H Yielding Interesting Results (Possible H related ESR Site) ? Light Soaking at 77 K for Long Times Initiated
Venue
Sources	Colorado School of Mines, Golden, CO; University of Utah
Document Type	Presentation (Powerpoint presentation)
Resource Date	04/17/2006

Post Date	11/11/2005
Title	THIN FILM PV PARTNERSHIP PROGRAM 2005
Link	(PowerPoint 10.8 MB)
Author	K. Zweibel
Description	Overview of the purpose, strategies, and goals of the Thin Film Partnership Program, including updated module, BOS, and system cost projections for 2005 and 2020.
Venue	2005 DOE Solar Review
Source	National Renewable Energy Laboratory
Document Type	Presentation (Powerpoint presentation)
Resource Date	11/10/2005

Post Date	11/17/2005
Title	HOLE MOBILITY LIMITS FOR AMORPHOUS AND NANOCRYSTALLINESILICON SOLAR CELLS
Link	(PDF 288 KB) Download Acrobat Reader.
Author	E. A. Schiff
Description	Themes of this Presentation (1) Describe ?minority carrier mobility limitation? concept for pinsolar cells. For low-mobility absorbers, the magnitude of recombination parameters can have very little effect. (2) Describe experimental testing of hole mobility limited description for United Solar OvonicCorp.?s a-Si:H solar cells and answer ?what happens" questions about initial state of a-Si:H and nc-Si:H solar cells: if (a) mobility was improved; if (b) recombination was reduced; (c) Why are nc-Si:H solar cells about 2 microns thick? (3) Apply description to the light-soaking problem: (a) Modest defect recombination plays well with H-collision. (b) Suggests that light-soaking in United Solar Ovoniccells is self-limiting
Venue	Solar Technology Review Meeting, Denver, 11/7-10/2005, Denver, CO, presentation by Syracuse University
Source	Syracuse University
Document Type	Presentation (Adobe Postscript file)
Resource Date	11/2005

Post Date	11/18/2005
Title	HOT AND HUMID THIN FILM MODULE TESTING IN FLORIDA
Link	(JPG 1.2 MB)
Author	N. G. Dhere
Description	various arrays are tested
Venue	DOE Solar Review 2005 poster
Source	FLorida Solar Energy Center
Document Type	Presentation (JPG image)
Resource Date	11/2005

Post Date	11/23/2005
Title	NANOSCALE-DESIGNED CERAMIC FILMS
Link	(PDF 1.9 MB) Download Acrobat Reader.
Author	S. Sambasivan
Description	thermal barriers, conformal alumina films, epitaxial oxide growth
Venue	Nanocommerce 2004, Chicago
Source	Applied thin films
Document Type	Presentation (Adobe Postscript file)
Resource Date	10/2005

Post Date	09/02/2005
Title	PV PAST THE TIPPING POINT
Link	(PowerPoint 31.8 MB)
Author	K. Zweibel
Description	Photovoltaics is growing rapidly, coming down in cost, and technical progress is substantial. We can be assured that PV costs will come down enough to provide electricity at an energy signifiant level.
Venue	Presntation at NREL to Norwegian StudyTour sponsored by CSM August 31, 2005
Source	National Renewable Energy Laboratory
Document Type	Presentation (Powerpoint presentation)
Resource Date	08/31/2005

Post Date	07/28/2005
Title	2002 TO 2005 THIN FILM PARTNERSHIP BUDGET TRENDS
Link	(PowerPoint 38 KB)
Author	K. Zweibel
Description	Budget in thin films for subcontracts is down 36% since 2002.
Venue
Source	National Renewable Energy Laboratory
Document Type	Presentation (Powerpoint presentation)
Resource Date	07/2005

Post Date	07/20/2005
Title	ATTENDEE LIST NATIONAL A-SI AND THIN FILM SI R&D TEAM MEETING MAY 19-20, 2005
Link	(PDF 50 KB) Download Acrobat Reader.
Author	B. Von Roedern
Description	List (with phone, email) of attendees
Venue	19th a-Si national team meeting, NREL, 5/19+20/2005
Source	National Renewable Energy Laboratory
Document Type	Presentation (Adobe Postscript file)
Resource Date	05/20/2005

Post Date	07/19/2005
Title	A-SIGE - STABILIZED PERFORMANCE AND DEPOSITION RATE
Link	(PDF 250 KB) Download Acrobat Reader.
Author	G. Ganguly
Description	1. Silane instead of disilane at high rate 2. Higher temperature - less germanium 3. Grading optimized for higher rate deposited material
Venue	19th a-Si national team meeting, NREL, 5/19+20/2005
Source	Uni-Solar Ovonic
Document Type	Presentation (Adobe Postscript file)
Resource Date	05/20/2005

Post Date	07/19/2005
Title	VENUES AND DATES OF A-SI TEAM MEETINGS
Link	(MS Word 21 KB)
Author	B. Von Roedern
Description	List of venues and dates of NREL a-Si team Meetings, 1992 - 2005
Venue	19th a-Si national team meeting, NREL, 5/19+20/2005
Source	N/A
Document Type	Presentation (Word document)
Resource Date	05/20/2005

Post Date	07/19/2005
Title	THE EFFECTS OF LIGHT-INDUCED DEGRADATION ON THE ELECTRONIC PROPERTIES OF HYDROGENATED NANOCRYSTALLINESILICON
Link	(PDF 817 KB) Download Acrobat Reader.
Authors	J. D. Cohen, B. Yan, J. Yang, S. Guha
Description	?States observed using DLCP appear to be shallow and donor-like and their profile does not change significantly with light soaking ?Their distribution and density can be modified by hydrogen profiling ?High quality optical spectra for nc-Si:H were obtained using transient photocapacitance spectroscopy ?Can separate the nc-Si:H component from the a-Si:H component by changing the measurement temperature ?Can determine an activation energy for minority carrier collection ?Light soaking leads to a degradation in minority carrier collection ?Our results are correlate with the observed degradation of electrical properties in nc-Si:H solar cells found after light exposure ?This degradation does not appear to involve an increase in the dangling bond density that can be observed in our sub-bandgap spectra
Venue	19th a-Si national team meeting, NREL, 5/19+20/2005
Sources	Uni-Solar Ovonic; University of Oregon
Document Type	Presentation (Adobe Postscript file)
Resource Date	05/20/2005

Post Date	07/19/2005
Title	STUDY OF VHF DEPOSITION OF NC-SI:H SOLAR CELLS
Link	(PDF 453 KB) Download Acrobat Reader.
Author	X. Deng
Description	Study of VHF deposition of nc-Si:H solar cells ? PECVD techniques using UT multi-chamber load-locked deposition system; ? Substrates: 10 cm x 10 cm stainless steel substrates coated with Ag/ZnO back reflectors; ? 15nm a-Si:H n-layer and 20 nm nc-Si:H p-layer were prepared using the conventional 13.56 MHz RF-PECVD technique at deposition rates near 1 Å/s. ? Deposition parameters for nc-Si:H i-layers: ? VHF-PECVD technique with a frequency of 70 MHz and a power density of ~0.6 W/cm2; ? Substrate temperature Tsub in the range of 150 ?400 C; ? Gas mixtures of disilane/hydrogen with a grading gas mixture ratio [Si2H6/H2]: 1sccm/200sccm to 3sccm/200sccm; ? nc-Si:H i-layers with thicknesses of up to 3200 nm and deposition rates of up to 6.0 Å/s.
Venue	19th a-Si national team meeting, NREL, 5/19+20/2005
Source	University of Toledo
Document Type	Presentation (Adobe Postscript file)
Resource Date	05/20/2005

Post Date	07/19/2005
Title	RADICALS PRODUCING HW AND RF DISCHARGE DEPOSITION
Link	(PDF 61 KB) Download Acrobat Reader.
Author	A. Gallagher
Description	Radicals at the substrate, detected by threshold-ionization mass spectroscopy.
Venue	19th a-Si national team meeting, NREL, 5/19+20/2005
Source	NIST
Document Type	Presentation (Adobe Postscript file)
Resource Date	05/20/2005

Post Date	07/19/2005
Title	NEW APPROACHES FOR CHARACTERIZING THE CREATION AND ANNEALING OF DEFECT STATES IN FILMS AND SOLAR CELLS
Link	(PDF 714 KB) Download Acrobat Reader.
Authors	C. Wronski, R. W. Collins, J. Deng, N. Podraza
Description	?Direct correlations between results on films and cells with corresponding i-layers have been obtained ?Cumulative evolution of metastable gap states in i layers with regions having t^1/3dependence is observed ?Evolution of purely metastable defects, however, has a clear t^1/2 dependence ?A t^-1/3 dependence for changes in photoconductivities is found not to hold for recombination through gap states located around midgap ?The relation G^2t=constant for degraded states is found to hold for midgap recombination in films and solar cells ?Surprising large room temperature annealing out of defect states around midgap has been observed after 1 sun illumination in both films and cells ?Annealing kinetics point to the contribution of at least two different processes ?The systematic increase in suppression of annealing with higher photogenerated carrier concentration runs contrary to the proposed ?light induced annealing? phenomenon proposed for 1 sun and higher illuminations
Venue	19th a-Si national team meeting, NREL, 5/19+20/2005
Source	Pennsylvania State University
Document Type	Presentation (Adobe Postscript file)
Resource Date	05/20/2005

Post Date	07/20/2005
Title	LIGHT-SOAKING AND OPEN-CIRCUIT VOLTAGES IN SOLAR CELLS: INSIGHTS INTO A-SI:H METASTABILITY
Link	(PDF 679 KB) Download Acrobat Reader.
Authors	E. A. Schiff, S. Guha, B. Yan, J. Yang
Description	Summary of our Conclusions About United Solar a-Si:H Solar Cells 1. Photocarrier recombination fits the usual bandtail+defect picture @ solar intensities - but As-deposited: primarily bandtail Light-soaked: bandtail perturbed by defects 2. Recombination processes probably drive light-soaking. Kinetics (?t^1/3?) mostly agrees with: Hydrogen-collision Driven by bandtail recombination 3. Tail/defect Crossover between bandtail & defect recombination appears to be on the same timescale as ?light-induced annealing.?
Venue	19th a-Si national team meeting, NREL, 5/19+20/2005
Sources	Syracuse University; Uni-Solar Ovonic
Document Type	Presentation (Adobe Postscript file)
Resource Date	05/20/2005

Post Date	07/19/2005
Title	LIGHT-INDUCED METASTABILITY IN HYDROGENATED NANOCRYSTALLINE SILICON SOLAR CELLS
Link	(PDF 2.6 MB) Download Acrobat Reader.
Authors	B. Yan, J. Yang, S. Guha
Description	Outline 1. Review of the results reported in the last team meeting (a) spectral dependence of light-induced degradation in nc-Si:H solar cells 2. New experimental results-Electrical bias dependence (a) Forward current injection (b) Light-soaking under reverse bias 3. Microscopic Model for the metastability in nc-Si:H solar cells
Venue	19th a-Si national team meeting, NREL, 5/19+20/2005
Source	Uni-Solar Ovonic
Document Type	Presentation (Adobe Postscript file)
Resource Date	05/20/2005

Post Date	07/20/2005
Title	HOLE DRIFT & MICROCRYSTALLINE SILICON SOLAR CELLS
Link	(PDF 348 KB) Download Acrobat Reader.
Authors	T. Dylla, F. Finger, E. A. Schiff
Description	The physics of hole drift in solar-grade nc-Si:H is consistent with valence bandtail trapping. ?Band mobility about the same as a-Si:H ?Bandtail width somewhat narrower (30 meV vs. 40 meV) ?Attempt frequency much lower (10^9 s-1) Amorphous silicon solar cells are low-mobility type (slow carrier mu<< 1 cm2/Vs). Microcrystalline silicon solar cells are near the crossover between low & high mobility types (slow carrier mu about 1 cm2/Vs)
Venue	19th a-Si national team meeting, NREL, 5/19+20/2005
Sources	Forschungszentrum Juelich; Syracuse University
Document Type	Presentation (Adobe Postscript file)
Resource Date	05/20/2005

Post Date	07/19/2005
Title	HIGHLY REFLECTIVE AND HIGHLY TEXTURED AL/AG/ZNO BACK REFLECTOR FOR A-SI BASED SOLAR CELLS
Link	(PDF 1.1 MB) Download Acrobat Reader.
Author	X. Deng
Description	? High efficiency solar cells require high performance back reflector that is both highly textured and highly reflective ? Metal (Al or Ag) deposited at high temperature and low rate is usually highly textured but not as reflective ? Metal (Al or Ag) deposited at low temperature and high rate is usually highly reflective but not textured ? Ag has higher reflectance than Al at wavelength (600-1000nm) ? Used Al (deposited at relatively low Ts) and Ag (deposited at low Ts) to form stacked structure to enhance both texture and reflectance
Venue	19th a-Si national team meeting, NREL, 5/19+20/2005
Source	University of Toledo
Document Type	Presentation (Adobe Postscript file)
Resource Date	05/20/2005

Post Date	07/20/2005
Title	FABRICATION AND OPTICAL ANALYSIS OF THE ZNO/AG BACKREFLECTOR STRUCTURE
Link	(PDF 508 KB) Download Acrobat Reader.
Authors	R. W. Collins, J. Deng, C. Wronski, N. Podraza
Description	Goal 1: Identify the origins of losses in Ag/ZnO and Al/ZnO back-reflectors and mitigate these losses through metal/ZnO deposition and processing. Goal 2: Combine novel optical designs with low-loss back-reflectors to minimize overall reflection losses in the near-infrared Origin of Losses in Back-Reflector 1. Optical absorption in the ZnO and metal due to their intrinsic properties Chemical intermixing at the metal/ZnO interface leading to absorption losses 2. Physical intermixing due to surface roughness at the metal/ZnO interface leading to absorption losses, including plasmon resonances 3. General back reflector design leading to enhanced reflection
Venue	19th a-Si national team meeting, NREL, 5/19+20/2005
Sources	Pennsylvania State University; University of Toledo
Document Type	Presentation (Adobe Postscript file)
Resource Date	05/20/2005

Post Date	07/19/2005
Title	EX-SITU SPECTROSCOPIC ELLIPSOMETRY (SE) STUDY FOR INTRINSIC LAYER
Link	(PDF 38 KB) Download Acrobat Reader.
Authors	X. Deng, R. W. Collins
Description	? SE allows us to study the structural properties (a-Si, void, nc-Si volume fractions) at different level of growth. ? This particular data shows the effect of change in hydrogen dilution ratio for a i-ncSi layer deposited with graded dilution profile. ? By increasing the [Si2H6]/[H2] ratio during growth, the trend to increase in fc has been suppressed. ? Applying the same for in-situ growth, we can exactly control the required structural property of the i-layer in near future.
Venue	19th a-Si national team meeting, NREL, 5/19+20/2005
Source	University of Toledo
Document Type	Presentation (Adobe Postscript file)
Resource Date	05/20/2005

Post Date	07/19/2005
Title	ELECTRONIC PROPERTIES OF THE NREL LOW FILAMENT TEMPERATURE HWCVD AMORPHOUS SILICON GERMANIUM ALLOYS
Link	(PDF 976 KB) Download Acrobat Reader.
Author	J. D. Cohen
Description	We have found superior electronic properties for NREL HWCVD a-Si,Ge:H alloys grown using lower filament temperatures. In particular these samples exhibit sharp band tails and low midgap defect densities, comparable to the best PECVD a-Si,Ge:H samples. Electronic properties appear to be very sensitive to oxygen impurity levels, perhaps much more so than PECVD alloy samples. The minority hole collection appears to be less efficient than the best PECVD alloys in apparent contradiction to the above results. *Preliminary degradation studies of the 29at.% Ge alloy sample indicate an unusual two-step defect creation kinetics.
Venue	19th a-Si national team meeting, NREL, 5/19+20/2005
Source	University of Oregon
Document Type	Presentation (Adobe Postscript file)
Resource Date	05/20/2005

Post Date	07/19/2005
Title	POLY-SI SEED LAYER PREPARED BY ALUMINUM-INDUCED CRYSTALLIZATION
Link	(PDF 3.1 MB) Download Acrobat Reader.
Authors	O. Ebil, S. S. Hegedus, R. W. Birkmire
Description	For the first time continuous poly-Si films on glass substrates was prepared by aluminum-induced crystallization during deposition of Si using HW-CVD. Continuous poly-Si films with a grain size / thickness ratio of 20 were obtained; 10 um average grain size for 500 nm thick Si films The optimum Si/Al thickness ratio was found to be 1. Increasing Si/Al ratio did not improve the average grain size or the thickness of the poly-Si film.
Venue	19th a-Si national team meeting, NREL, 5/19+20/2005
Source	University of Delaware
Document Type	Presentation (Adobe Postscript file)
Resource Date	05/20/2005

Post Date	07/20/2005
Title	DEVELOPMENT OF IMPROVED BACK REFLECTORS FOR AMORPHOUS SILICON-BASED MULTI-JUNCTION TECHNOLOGIES
Link	(PDF 658 KB) Download Acrobat Reader.
Author	S. Jones
Description	? Have been focusing on Al/Multi-layer/ZnO structure in which multi-layer is ZnOSi/Si/ZnOSi structure. ? Have demonstrated that for back reflectors without textured surfaces a significant improvement in cell performance was obtained using the multilayer structure.
Venue	19th a-Si national team meeting, NREL, 5/19+20/2005
Source	Energy Conversion Devices
Document Type	Presentation (Adobe Postscript file)
Resource Date	05/20/2005

Post Date	07/19/2005
Title	DEPOSITION PHASE DIAGRAMS FOR OPTIMIZATION OF THIN FILM SI:H AND SI1-XGEX:H
Link	(PDF 2.5 MB) Download Acrobat Reader.
Authors	C. Wronski, R. W. Collins, X. Deng
Description	1. Motivation 2. Background on interpretation: roughness evolution from RTSE 3. Experimental details: plasma-enhanced chemical vapor deposition (PECVD) 4. Summary of previous studies of Si:H: comparison of rf and vhf PECVD for high rate growth 5. Comparison of Si:H and Si1-xGex:H phase diagrams: standard deposition conditions 6. Comparison of Si1-xGex:H phase diagrams: effect of temperature 7. Comparison of Si:H and Si1-xGex:H phase diagrams: effect of electrode configuration 8. Summary and future directions
Venue	19th a-Si national team meeting, NREL, 5/19+20/2005
Sources	Pennsylvania State University; University of Toledo
Document Type	Presentation (Adobe Postscript file)
Resource Date	05/20/2005

Post Date	07/20/2005
Title	FUNDAMENTAL STUDIES OF NANOCRYSTALLINE SI AND GE FOR PV
Link	(PDF 178 KB) Download Acrobat Reader.
Author	V. L. Dalal
Description	?Growth chemistry of nc Si:H and Ge:H ?Why do some materials have <111> grain and some <220>? ?What controls grain size? How do we get larger grains? ?What are the mobilities in device-type structures? ?What are the diffusion lengths of minority carriers?
Venue	19th a-Si national team meeting, NREL, 5/19+20/2005
Source	Iowa State University
Document Type	Presentation (Adobe Postscript file)
Resource Date	05/20/2005

Post Date	07/19/2005
Title	HIGH RATE DEPOSITION OF NC-SI:H SOLAR CELLS AND ITS APPLICATION IN A-SI:H/NC-SI:H MULTI-JUNCTION STRUCTURE
Link	(PDF 2.2 MB) Download Acrobat Reader.
Authors	B. Yan, J. Yang, S. Guha
Description	Outline 1. Estimation of the required deposition time for manufacturing 2. Existing method for high rate deposition and our approaches with previous results 3. Current statues for nc-Si:H single-junction and a-Si:H/nc-Si:H double-junction solar cells 4. Summary and future work
Venue	19th a-Si national team meeting, NREL, 5/19+20/2005
Source	Uni-Solar Ovonic
Document Type	Presentation (Adobe Postscript file)
Resource Date	05/20/2005

Post Date	07/19/2005
Title	IMPROVED BACK REFLECTOR FOR HIGH EFFICIENCY HYDROGENATED AMORPHOUS AND NANOCRYSTALLINE SILICON BASED SOLAR CELLS
Link	(PDF 2.8 MB) Download Acrobat Reader.
Authors	B. Yan, J. Yang, S. Guha
Description	Experimental 1. Ag/ZnO BR deposition: Sputtering method 2. Chemical etching: 0.5% HCl 3. Surface morphology measurement: AFM at NREL 4. Light scattering measurement: He-Ne laser, measure the scattered light at different angles 5. Solar cell qualification: a-SiGe:H single-junction, nc-Si:H single-junction, and a-Si:H/a-SiGe:H/nc-Si:H triple-junction cells made using RF glow discharge
Venue	19th a-Si national team meeting, NREL, 5/19+20/2005
Source	Uni-Solar Ovonic
Document Type	Presentation (Adobe Postscript file)
Resource Date	05/20/2005

Post Date	07/19/2005
Title	A-SIGE:H FILMS AND DEVICES DEPOSITED BY HWCVD AT LOW FILAMENT TEMPERATURES
Link	(PDF 2.0 MB) Download Acrobat Reader.
Authors	A. H. Mahan, Y. Xu, R. C. Reedy, H. M. Branz, B. Yan
Description	Outline of presentation - Structure of HWCVD a-SiGe:H films quite different than that previously reported for PECVD films - We have an oxygen (O) contamination problem that has definitely impacted our film properties, and by implication our device results - In spite of our O contamination, our device results are improved relative to those deposited previously - give you one interpretation of our O ?source?
Venue	19th a-Si national team meeting, NREL, 5/19+20/2005
Source	National Renewable Energy Laboratory
Document Type	Presentation (Adobe Postscript file)
Resource Date	05/20/2005

Post Date	07/19/2005
Title	NC-SI BASED SOLAR CELLS
Link	(PDF 299 KB) Download Acrobat Reader.
Authors	G. Ganguly, B. Yan, J. Yang
Description	1. Pressure dependence of nc-Si cells (50 min.) 2. 0.25, 45 and 460cm2 a-Si/nc-Si tandem cells 3. Degradation behavior of a-Si vs. a-Si/nc-Si 4. Degradation of nc-Si cells vs. Voc & H-diln.
Venue	19th a-Si national team meeting, NREL, 5/19+20/2005
Source	Uni-Solar Ovonic
Document Type	Presentation (Adobe Postscript file)
Resource Date	05/20/2005

Post Date	07/20/2005
Title	A NEW APPROACH TO CRYSTAL SILICON THIN FILMS ON GLASS
Link	(PDF 1.0 MB) Download Acrobat Reader.
Authors	C. Teplin, H. M. Branz, R. C. Reedy, H. Moutinho
Description	The template/c-Si interface: Goal: Attain a silicon seed layer with biaxial texturing Potential template materials: CeO2, NiSi, CoSi, ZrO2, TiN
Venue	19th a-Si national team meeting, NREL, 5/19+20/2005
Source	National Renewable Energy Laboratory
Document Type	Presentation (Adobe Postscript file)
Resource Date	05/20/2005

Post Date	07/20/2005
Title	CRYSTALLIZATION OF A-SI FOR SOLAR CELL APPLICATIONS
Link	(PDF 1.4 MB) Download Acrobat Reader.
Authors	Q. Wang, H. M. Branz, R. C. Reedy, Y. Xu
Description	Outline ? Solid phase crystallization of a-Si:H on glass ? Crystal Si on glass module gets 8-9% over 0.7 m2 (CSG). Absorber: p- ? SPC cell gets over 9% (Sanyo). Absorber: n- ? STAR cell gets 9.8% (Keneka). Absorber: i ? Crystallization of hot-wire a-Si:H ? Epi-Si on seed layer -> 15% ? ? Seed layers ? CeO2 and other foreign coatings (NREL) ? Metal induced Si seeds (hmi, UNSW) ? Solid phase epitaxy on c-Si ? In-situ monitoring for kinetics
Venue	19th a-Si national team meeting, NREL, 5/19+20/2005
Source	National Renewable Energy Laboratory
Document Type	Presentation (Adobe Postscript file)
Resource Date	05/20/2005

Post Date	06/01/2005
Title	PV STRATEGY PRESENTATION
Link	(PowerPoint 21.6 MB)
Author	S. Guha
Description	amorphous silicon, triple junctions, UniSolar, roofing material, peel-and-stick
Venue	Thin Film Partnership a-Si National R&D Team meeting
Source	Uni-Solar Ovonic
Document Type	Presentation (Powerpoint presentation)
Resource Date	05/2005

Post Date	02/09/2005
Title	LARGE AREA THIN FILM DEVICES: NONUNIFORMITIES, INTERFACIAL LAYESR, REACG-THROUGH EFFECTS
Link	(PowerPoint 884 KB)
Author	V. G. Karpov
Description
Venue	DOE Solar Review
Source	University of Toledo
Document Type	Presentation (Powerpoint presentation)
Resource Date	10/2004

Post Date	02/07/2005
Title	THIN FILMS AND THE SYSTEM DRIVEN APPROACH
Link	(PowerPoint 1.0 MB)
Author	K. Zweibel
Description	Cost analysis of thin films for semiconductor, encapusulation, layer thickness, and efficiency.
Venue	DOE and NREL Solar Review Meeting 2004
Source	National Renewable Energy Laboratory
Document Type	Presentation (Powerpoint presentation)
Resource Date	10/2004

Post Date	02/07/2005
Title	2ND GENERATION THIN FILMS
Link	(PowerPoint 8.9 MB)
Author	K. Zweibel
Description	Potential of CIS, CdTe, and a-Si thin films.
Venue	Rice University Solar Energy Workshop
Source	National Renewable Energy Laboratory
Document Type	Presentation (Powerpoint presentation)
Resource Date	09/2004

Post Date	04/22/2005
Title	EPV RELIABILITY UPDATE
Link	(PDF 633 KB) Download Acrobat Reader.
Author	K. W. Jansen
Description	a-Si and CIS module designs, stress tests, and reliability
Venue	Thin Film Module Reliability Meeting
Source	Energy Photovoltaics
Document Type	Presentation (Adobe Postscript file)
Resource Date	06/24/2004

Post Date	04/22/2005
Title	UNISOLAR MODULES
Link	(PDF 2.4 MB) Download Acrobat Reader.
Author	D. E. Parker
Description	Flexible a-Si modules used for various applications
Venue	Thin Film Module Reliability National Team meeting
Source	Uni-Solar Ovonic
Document Type	Presentation (Adobe Postscript file)
Resource Date	06/23/2004

Post Date	04/22/2005
Title	MOISTURE INGRESS PROTECTION BY COMBINED BACKSHEET AND ENCAPSULANT CONSTRUCTIONS
Link	(PDF 1.7 MB) Download Acrobat Reader.
Authors	G. J. Jorgensen, M. Kempe, C. Kennedy, K. Terwilliger
Description	WVTR, PET, EVA, BRP, TruSeal
Venue	Thin Film Module Reliability National Team Meeting
Source	National Renewable Energy Laboratory
Document Type	Presentation (Adobe Postscript file)
Resource Date	06/2004

Post Date	04/22/2005
Title	EFFECTS OF MOISTURE INGRESS ON PV MODULES
Link	(PDF 528 KB) Download Acrobat Reader.
Author	M. Kempe
Description	Measuring the rate water vapor moves through EVA from the edge and the back
Venue	Thin Film Module Reliability National Team Meeting
Source	National Renewable Energy Laboratory
Document Type	Presentation (Adobe Postscript file)
Resource Date	06/2004

Post Date	04/22/2005
Title	ADHESION TESTS OF CANDIDATE BACKSHEET AND ENCAPSULANTS
Link	(PDF 425 KB) Download Acrobat Reader.
Authors	G. J. Jorgensen, J. A. del Cueto, et al.
Description	Pull tests of various candidate replacements for EVA
Venue	Thin film module reliability national team meeting
Source	National Renewable Energy Laboratory
Document Type	Presentation (Adobe Postscript file)
Resource Date	06/2004

Post Date	04/22/2005
Title	LEAKAGE CURRENTS AND HIGH-VOLTAGE THIN FILM MODULES
Link	(PDF 1.1 MB) Download Acrobat Reader.
Author	N. G. Dhere
Description	FSEC testing of outdoor thin film arrays
Venue	Thin Film Module Reliability Team Meeting
Source	FLorida Solar Energy Center
Document Type	Presentation (Adobe Postscript file)
Resource Date	06/2004

Post Date	04/22/2005
Title	PAST AND PREDICTED THIN FILM MODULE PRODUCTION IN THE US BY TECHNOLOGY
Link	(PowerPoint 45 KB)
Author	K. Zweibel
Description	Annual MWp/yr 2000-2011 by technology
Venue
Source	National Renewable Energy Laboratory
Document Type	Presentation (Powerpoint presentation)
Resource Date	04/22/2004

Post Date	02/11/2005
Title	PV MODULE RECYCLING IN THE US
Link	(PowerPoint 3.8 MB)
Authors	V. Fthenakis, K. Zweibel
Description	Recycling today and tomorrow.
Venue	EU Workshop "Waste Challenge"
Sources	Brookhaven National Laboratory; National Renewable Energy Laboratory
Document Type	Presentation (Powerpoint presentation)
Resource Date	03/2004

Post Date	02/11/2005
Title	PV MODULE RECYCLING IN THE US
Link	(PDF 600 KB) Download Acrobat Reader.
Authors	V. Fthenakis, K. Zweibel
Description	Recycling today and tomorrow
Venue	EIA Workshop
Source	N/A
Document Type	Presentation (Adobe Postscript file)
Resource Date	03/2004

Post Date	02/07/2005
Title	PV AS A MAJOR SOURCE OF GLOBAL ELECTRICITY
Link	(PowerPoint 13.2 MB)
Author	K. Zweibel
Description	Projected improvements needs to make PV a major source of electricity.
Venue	University of Toledo
Source	National Renewable Energy Laboratory
Document Type	Presentation (Powerpoint presentation)
Resource Date	02/24/2004

Post Date	02/17/2005
Title	A COMPARISON OF THIN FILMS AND X-SI IN THE US MARKET, HISTORICAL AND PROJECTED
Link	(MS Word 31 KB)
Author	K. Zweibel
Description	Thin films are gaining ground on x-Si and are projected to overtake it in the US about 2010-2011.
Venue	Thin Film Partnership and Paul Maycock's PV News February 2005
Source	PV News
Document Type	Presentation (Word document)
Resource Date	02/17/2004

Post Date	05/10/2005
Title	PHASE ENGINEERING OF HIGH EFFICIENCY A-SI SOLAR CELLS
Link	(PowerPoint 4.5 MB)
Authors	R. W. Collins, C. Wronski, et al.
Description	protocrystalline silicon phase boundary
Venue	a-Si National R&D Team meeting
Source	Pennsylvania State University
Document Type	Presentation (Powerpoint presentation)
Resource Date	2004

Post Date	03/07/2005
Title	MASSIVE PARALLEL PROCESSING FOR LOW COST A-SI PRODUCTION
Link	(PDF 526 KB) Download Acrobat Reader.
Authors	A. E. Delahoy, et al.
Description	ABSTRACT: A large batch approach to the manufacturing of amorphous silicon photovoltaic modules is described. A cost analysis shows the cost of production to lie in the range $1-2/W p depending largely on the labor content. The consistency and reproducibility of this approach is illustrated with statistical production data. The longevity of the module is demonstrated by long-term exposure data. Recent improvements in module performance are documented. The influence of spectral variation on the energy delivery of tandem junction modules is quantified. Keywords: a-Si, Module Manufacturing, Cost Reduction, Performance...
Venue	Presentation
Source	Energy Photovoltaics
Document Type	Presentation (Adobe Postscript file)
Resource Date	2004

Post Date	01/21/2005
Title	IMPLEMENTATION OF A COMPREHENSIVE ON-LINE CLOSED-LOOP DIAGNOSTIC SYSTEM FOR ROLL-TO-ROLL AMORPHOUS SILICON SOLAR CELL PRODUCTION
Link	(PDF 6.1 MB) Download Acrobat Reader.
Author	T. Ellison
Description	Development and implementation of in situ monitoring on in-line stainless steel a-Si processing line
Venue	ECD and United Solar PV Manufacturing R&D Program Annual Review 2003
Source	Energy Conversion Devices
Document Type	Presentation (Adobe Postscript file)
Resource Date	08/28/2003

Post Date	03/07/2005
Title	IMPLEMENTATION OF A COMPREHENSIVE ON-LINE CLOSED-LOOP DIAGNOSTIC SYSTEM FOR A ROLL-TO-ROLL AMORPHOUS SILICON SOLAR CELL PRODUCTION
Link	(PDF 6.2 MB) Download Acrobat Reader.
Author	T. Ellison
Description	Introduction-- ECD and United Solar-- ECD/United Roll-to-Roll Production Technology-- Impact of NREL PV MaT/Man Funding Summary of Phase I of the PV Man R&D 6 program Task I Task II: Component Cell PVCD development - for use in future continuous online optimization Task III: Plasma Diagnostics/Improved Deposition Technology Task IV: Yield Improvements: Substrate Cleaning - prove efficacy of plasma cleaning and get rid of washing machine.
Venue	NREL-Annual Review
Source	Energy Conversion Devices
Document Type	Presentation (Adobe Postscript file)
Resource Date	08/28/2003

Post Date	02/08/2005
Title	DEVICE DESIGN AND EFFICIENCY SUBTEAM REPORT
Link	(PDF 616 KB) Download Acrobat Reader.
Authors	S. Jones, et al.
Description	Team Priorities
Venue	Presented at the 17th a-Si National R&D Team Meeting
Source	Energy Conversion Devices
Document Type	Presentation (Adobe Postscript file)
Resource Date	08/08/2003

Post Date	05/24/2005
Title	AMORPHOUS AND MICROCRYSTALLINE SILICON SOLAR CELLS - A STATUS REVIEW
Link	(PDF 454 KB) Download Acrobat Reader.
Author	X. Deng
Description	Presentation of U. Toledo's a-Si and nc-Si cell status
Venue	NCPV and Solar Program Review Meeting, March 24-26, 2003, Denver, CO
Source	University of Toledo
Document Type	Presentation (Adobe Postscript file)
Resource Date	03/26/2003

Post Date	02/07/2005
Title	PROGRESS IN US PV
Link	(PowerPoint 1.5 MB)
Author	T. Surek
Description	50 years of progress in PV.
Venue	Osaka IEEE conference
Source	National Renewable Energy Laboratory
Document Type	Presentation (Powerpoint presentation)
Resource Date	2003

Annual/Final Reports

Post Date	07/09/2008
Title	PROCESSING MATERIALS, DEVICES AND DIAGNOSTICS FOR THIN FILM PHOTOVOLTAICS: FUNDAMENTAL AND MANUFACTURABILITY ISSUES
Link	(PDF 4.2 MB) Download Acrobat Reader.
Authors	R. W. Birkmire, W. N. Shafarman, E. Eser, S. S. Hegedus, B. E. McCandless, K. D. Dobson, S. Bowden
Description	This report describes results achieved during phase V of a V-phase subcontract to develop and understand thin film solar cell technology associated to CuInSe2 and related alloys, a-Si and its alloys and CdTe. This includes application of a-Si to c-Si wafer-type cells as well. Modules based on all these thin films are promising candidates to meet DOE long-range efficiency, reliability and manufacturing cost goals. The critical issues being addressed under this program are intended to provide the science and engineering basis for the development of viable commercial processes and to improve module performance. The generic research issues addressed are: 1) quantitative analysis of processing steps to provide information for efficient commercial scale equipment design and operation; 2) device characterization relating the device performance to materials properties and process conditions; 3) development of alloy materials with different bandgaps to allow improved device structures for stability and compatibility with module design; 4) development of improved window/heterojunction layers and contacts to improve device performance and reliability; and 5) evaluation of cell stability with respect to illumination, temperature and ambient and with respect to device structure and module encapsulation.
Venue	Institute of Energy Conversion (U. Delaware), Subcontract No. ADJ-1-30630-12, annual report
Source	University of Delaware
Document Type	Annual Report (Adobe Postscript file)
Resource Date	04/01/2008

Post Date	10/11/2007
Title	INNOVATIVE CHARACTERIZATION OF AMORPHOUS AND THIN-FILM SILICON FOR IMPROVED MODULE PERFORMANCE
Link	(PDF 982 KB) Download Acrobat Reader.
Author	J. D. Cohen
Description	We have worked to characterize the electronic properties of nc-Si:H materials obtained from United Solar. An extensive set of of new sample devices were obtained, all of which were actual working n-i-p solar cell devices. These were all deposited on specular stainless-steel under four different types of hydrogen profiling, and each deposition contained samples with varying degrees of crystalline fractions. Our data suggested that the degree of crystallinity in these nc-Si:H samples, rather than the hydrogen profiling function itself, was the strongest factor determining the defect response in our junction capacitance measurements. We also found that the samples that contained a higher fraction of amorphous component, as determined from Raman spectroscopy, exhibited the highest resilience to light-induced deep defect creation indicating an actual slight decrease in defect response as shown by DLCP measurements. This agrees with our measurements reported last year. On the other hand, the samples with estimated crystalline fractions above 60vol.% exhibited quite a pronounced increase of deep defects after light soakIn spite of this, all of the sample devices exhibited a decrease in performance after light soaking with 610nm filtered ELH light. Further studies are being pursued to test a degradation model over the wider range of nc-Si:H samples received during this past year. We have been studying in detail the set HWCVD a-Si,Ge:H alloys deposited at NREL by Yueqin Xu in which controlled levels of oxygen impurities were introduced, ranging from below 1019cm-3 to roughly 5 × 1020cm-3. This past year we discovered that the oxygen was responsible for a distinct deep defect, with an optical transition lying roughly 1.3 to 1.4 eV above the valence band. We hypothesize that the observed oxygen impurity related defect state may be associated with a positively charged oxygen donor level, possibly the previously suggested three fold coordinated oxygen center (O3+). Moreover, because the electrons excited into this defect remain trapped for roughly 0.5s at temperatures up to 370K, this strongly implies that there must exist a large barrier to their subsequent thermal emission into the conduction band. Follow up studies will try to pin down the thermal emission energy of the electron into the conduction in order to construct a configurational coordinate diagram for the transitions involving this defect. Also, we will examine samples containing a wider range of Ge alloy fractions to ascertain whether Ge itself may be playing a central role in the appearance of this defect. We used our junction capacitance methods to study the effect of Na on CIGS thin film solar cells. Our DLCP measurements revealed an increased free carrier density with the addition of Na and an activated bulk defect in CIGS absorber. However, neither could account for the >40% increase in efficiency with the addition of Na. The sub-band-gap TPC spectra showed a broader defect band and a steeper Urbach energy with the addition of Na which implies an increase in the carrier mobilities, but this again was not expected to lead to differences in performance consistent with the observations. Ultimately, forward bias admittance measurements revealed the existence of a large defect density at the CdS/CIGS heterojunction for the lower Na sample. It is interesting to note that SIMS profiles showed the Na moving towards the front of the cell when it is intentionally added. Finally, we argued that such a defect could readily explain the loss in VOC in the sample with reduced Na, and would be consistent with the observed admittance and DLCP behavior for this sample. Thus, it appears that it is the passivation of these interfacial defects that primarily accounts for the beneficial effects of Na toward the increased performance of the CIGS solar cells fabricated at IEC.ing.
Venue	University of Oregon, subcontract ZXL-5-44205-11, annual report
Source	University of Oregon
Document Type	Annual Report (Adobe Postscript file)
Resource Date	08/2007

Post Date	08/14/2007
Title	HIGH-EFFICIENCY AMORPHOUS SILICON AND NANOCRYSTALLINE SILICON-BASED SOLAR CELLS AND MODULES
Link	(PDF 1.0 MB) Download Acrobat Reader.
Authors	S. Guha, J. Yang
Description	We have achieved an aperture-area stable efficiency of 8.6% on an a-Si:H/a-SiGe:H/a-SiGe:H triple-junction solar cell deposited under the manufacturing constraints on an Al/ZnO back reflector made in the manufacturing line. The cell was encapsulated using a procedure similar to the manufacturing process. We have investigated deposition parameters for a-Si:H and a-SiGe:H deposition with MVHF at high rates. We found that the performance and stability of a-Si:H single-junction cells deposited with MVHF do not depend on the deposition rate in the range of 1-15 Å/s. We have achieved active-area (0.25 cm^2) initial and stable efficiencies of 9.0% and 8.5%, respectively, for nc-Si:H single-junction cells made with MVHF at a high rate ~ 5-8 Å/s. We have achieved active-area (0.25 cm^2) initial and stable efficiencies of 14.1% and 13.3%, respectively, for an a-Si:H/nc-Si:H/nc-Si:H triple-junction cell, where the top cell was made using RF at a low rate ~ 1 Å/s, and the nc-Si:H middle and bottom cells using MVHF at a high rate ~ 5-8 Å/s. We have demonstrated that an optimized hydrogen dilution profiling not only improves the initial nc-Si:H cell performance but also the stability against light soaking.
Venue	United Solar Ovonic LLC, subcontract ZXL-6-44205-14, first Annual Report
Source	Uni-Solar Ovonic
Document Type	Annual Report (Adobe Postscript file)
Resource Date	07/2007

Post Date	05/30/2007
Title	INNOVATIVE CHARACTERIZATION OF AMORPHOUS AND THIN-FILM SILICON FOR IMPROVED MODULE PERFORMANCE
Link	(PDF 230 KB) Download Acrobat Reader.
Author	P. C. Taylor
Description	During Phase II of the current sub-contract we have made significant progress in understanding the role of SiH2 in both high and low defect-density films of a-Si:H. We have also calculated the H-H separation at SiH2 sites that may be consistent with that observed in NMR light-soaking experiments.
Venue	University of Utah, subcontract XXL-5-44205-09, Phase 2 Annual Report
Source	University of Utah
Document Type	Annual Report (Adobe Postscript file)
Resource Date	05/2007

Post Date	07/25/2006
Title	INNOVATIVE CHARACTERIZATION OF AMORPHOUS AND THIN-FILM SILICON FOR IMPROVED MODULE PERFORMANCE
Link	(PDF 1.3 MB) Download Acrobat Reader.
Author	J. D. Cohen
Description	Our work has focused on three areas of study. First, we used transient photocapacitance (TPC) spectroscopy, transient photocurrent (TPI) and drive-level capacitance profiling (DLCP) to characterize the electronic properties of hydrogenated nanocrystalline Si (nc-Si:H) within a set of working n-i-p solar cell devices produced at United Solar Ovonics Corporation. Because the nc-Si:H layers in these more recent samples appear to be somewhat more intrinsic than those studied previously, with electron carrier densities estimated to lie below 1015 cm-3, we were able to obtain a definite deep defect response in our DLCP measurements for some of the samples. Surprisingly, this defect signal was observed to decrease after light-soaking rather than increase. Second, we continued our studies of the lower filament temperature HWCVD a-Si,Ge:H alloys being developed at NREL. These samples have revealed very good electronic properties. However, some later samples were of definite poorer quality and this appeared to be a result of excess oxygen contamination. The source of this contamination was identified and eliminated in the Fall, 2005, and we were then able to obtain a series of samples for study with different levels of oxygen introduced in a controlled manner using a variable air-leak. Surprisingly, these samples did not show a deterioration of electronic properties as a result of increasing oxygen levels. Moreover, the samples with moderate levels of oxygen actually revealed smaller Urbach energies, to below 40meV in one case. We also began examining the kinetics of light-induced degradation and annealing in these samples. It appears that these kinetics are somewhat different than those obtained in high quality PECVD a-Si,Ge:H films. In particular, the metastable deep defects anneal away over a much narrower ranges of temperatures than the PECVD a-Si,Ge:H films, suggested a narrower range of energy barriers for metastable defect recovery. Third, we applied both admittance and DLCP measurements to a set of CIGS photovoltaic devices that were obtained from Miguel Contreras at NREL. We examined eight devices that varied in their level of performance, from about 14.4% to nearly 17.5% efficiency. Admittance measurements carried out at zero volts applied bias did not reveal significant differences among this set of films. In particular, they did not reveal any variations in the deep acceptor capacitance step that some studies have found to be an indicator of device efficiencies. However, the DLC profiles on this set of NREL samples did indicate major differences. In particular, the DLCP determined defect density obtained under forward bias conditions, probing the defects in the region closest to the barrier interface, appeared to be reasonably well correlated to the device efficiencies across this set of samples.
Venue	University of Oregon, subcontract ZXL-5-44205-11, Annual Report
Source	University of Oregon
Document Type	Annual Report (Adobe Postscript file)
Resource Date	07/05/2006

Post Date	07/25/2006
Title	INNOVATIVE CHARACTERIZATION OF AMORPHOUS AND THIN-FILM SILICON FOR IMPROVED MODULE PERFORMANCE
Link	(MS Word 2.6 MB)
Author	P. C. Taylor
Description	We initiated collaborations with United Solar Ovonics Corporation on defects that contribute to the Staebler-Wronski effect in modules made using a-Si:H and a-SixGe1-x:H intrinsic layers. Specifically, we received a second set of device-quality samples, half of which have been light soaked. We are performing our NMR experiments on these two samples to confirm our earlier results on the metastable hydrogen doublet site at better signal-to-noise ratios. We are continuing our collaborations with NREL on defects generated in tritiated a-Si:H and have submitted a paper for publication. In addition, we have initiated studies of light soaking at 77 K to determine if the Staebler-Wronski effect saturates at this temperature or grows continuously as occurs in the case of the tritium decay in the tritiated samples.
Venue	U.Utah and Colorado School of Mines, subcontract XXL-44205-09, Annual report
Sources	Colorado School of Mines, Golden, CO; University of Utah
Document Type	Annual Report (Word document)
Resource Date	06/25/2006

Post Date	06/02/2006
Title	DOE SOLAR ENERGY TECHNOLOGY PROGRAM FY2005 ANNUAL REPORT
Link	(PDF 5.2 MB) Download Acrobat Reader.
Author	N/A
Description	The majority of the Program?s budget is allocated to PV research and development (R&D). All PV devices convert sunlight directly into electricity. However, there is a variety of materials and processes for creating PV devices, each with its own benefits and drawbacks. The major trade-off is between cost and sunlight-to-electricity conversion efficiency?higher efficiency typically translates into higher cost. Program participants consistently achieve world-record efficiencies for different types of PV, but each effort has the same ultimate goal: optimizing cost and efficiency to produce the least expensive end-use electricity.
Venue	DOE/GO-102006-2314May 2006
Source	National Renewable Energy Laboratory
Document Type	Annual Report (Adobe Postscript file)
Resource Date	05/2006

Post Date	04/10/2006
Title	FULFILLING THE PROMISE OF THIN FILM PV
Link	(PDF 5.5 MB) Download Acrobat Reader.
Author	K. Zweibel
Description	The Thin Film PV Partnership spearheads R&D on emerging thin film PV technologies. Led by the National Center for Photovoltaics and NREL, the Partnership leverages the combined efforts of the thin film PV industry, universities, and government research institutes.
Venue	Brochure excerpt
Source	National Renewable Energy Laboratory
Document Type	Annual Report (Adobe Postscript file)
Resource Date	04/2006

Post Date	04/11/2006
Title	TRANSPORT, INTERFACES, AND MODELING IN AMORPHOUS SILICON BASED SOLAR CELLS
Link	(MS Word 2.1 MB)
Author	E. A. Schiff
Description	In this report we present the status of three tasks of this research project: 1. Amorphous Silicon Solar Cell Characteristics and Modeling 2. Photocarrier Drift Mobility Measurements in a-Si:H and CIGS 3. Hole-Conducting Polymers as p-layer Materials for Amorphous and Crystal Silicon Solar Cells. In particular for the first project, we have published fairly extensively (see the references and the associated web-links at the end of this report. )
Venue	Syracuse University, Subcontract NDJ-2-30630-24 Annual Report
Source	Syracuse University
Document Type	Annual Report (Word document)
Resource Date	02/2006

Post Date	02/01/2006
Title	THIN FILM PV PARTNERSHIP
Link	(MS Word 393 KB)
Author	K. Zweibel
Description	Objectives Support the near-term transition to first-time manufacturing and commercial introduction of reliable thin-film a-Si, CIS, CdTe, and film silicon modules. Build a technology base upon which these advanced PV technologies can successfully improve manufacturing and continue to progress in terms of performance, reliability, and reduced cost for products meant to compete in the PV marketplace. Sustain innovation to support progress toward ambitious long-term PV cost and performance goals (e.g., 15% modules at under $50/m2 and capable of lasting 30 years) appropriate for cost-competitive PV electricity. Accomplishments Four JOULE milestones were met. Two Technology Partners broke ground on major manufacturing expansions (First Solar 50 MWp, and Uni-Solar 25 MWp). Production of thin films in the United States grew from 12 MWp in 2003 to an estimated >40 MWp in 2005. Future Directions · Continue to address key issues supporting the transition to successful first-time manufacturing or major production expansion in each thin film. · Significantly reduce CIS and CdTe layer thicknesses in cells and support transfer of this to manufacturing. · Direct CdTe research toward higher voltage. · Investigate nano-crystalline bottom cells for thin-film silicon multijunctions.___________________________________________
Venue	DOE NREL Annual Report
Source	National Renewable Energy Laboratory
Document Type	Annual Report (Word document)
Resource Date	02/2006

Post Date	02/07/2006
Title	DOE FY2007 CONGRESSIONAL BUDGET REQUEST FOR ENERGY SUPPLY AND CONSERVATION
Link	(PDF 3.4 MB) Download Acrobat Reader.
Author	N/A
Description	Appropriation Account Summary..........................................................................................................3 Appropriation Language ........................................................................................................................7 Energy Efficiency and Renewable Energy ..........................................................................................11 Electricity Delivery & Energy Reliability .........................................................................................511 Nuclear Energy .................................................................................................................................571 Environment, Safety and Health ........................................................................................................705 Legacy Management.........................................................................................................................733
Venue	The Department of Energy?s FY 2007 Congressional Budget justification is available on the Office of Chief Financial Officer/CFO homepage at http://www.mbe.doe.gov/budget
Source	Department of Energy
Document Type	Annual Report (Adobe Postscript file)
Resource Date	02/2006

Post Date	01/25/2006
Title	PROCESSING MATERIALS, DEVICES AND DIAGNOSTICS FOR THIN FILM PHOTOVOLTAICS: FUNDAMENTAL AND MANUFACTURABILITY ISSUES
Link	(MS Word 16.5 MB)
Author	R. W. Birkmire
Description	CdTe, CIS, CIGS, a-Si, thin Si
Venue	Annual Report to National Renewable Energy Laboratory under Subcontract No. ADJ-1-30630-129/05/04 to 9/04/05
Source	University of Delaware
Document Type	Annual Report (Word document)
Resource Date	01/2006

Post Date	11/11/2005
Title	A PROPOSED ROUTE TO THIN FILM CRYSTAL SI USING BIAXIALLY TEXTURED FOREIGN TEMPLATE LAYERS
Link	(PDF 165 KB) Download Acrobat Reader.
Author	C. W. Teplin
Description	We have developed a new approach to growing photovoltaic-quality crystal silicon (c-Si) films on glass. Other approaches to film c-Si focus on increasing grain size in order to reduce the deleterious effects of grain boundaries. Instead, we have developed an approach to align the silicon grains biaxially (both in and out of plane) so that 1) grain boundaries are ?lowangle? and have less effect on the electronic properties of the material and 2) subsequent epitaxial thickening is simplified. They key to our approach is the use of a foreign template layer that can be grown with biaxial texture directly on glass.
Venue	2005 DOE Solar Review
Source	National Renewable Energy Laboratory
Document Type	Annual Report (Adobe Postscript file)
Resource Date	11/2005

Post Date	02/17/2005
Title	PROCESSING MATERIALS, DEVICES AND DIAGNOSTICS FOR THIN FILM PHOTOVOLTAICS
Link	(MS Word 7.7 MB)
Authors	R. W. Birkmire, S. S. Hegedus, B. E. McCandless, W. N. Shafarman, et al.
Description
Venue	ADJ-1-30630-12 9/05/03 to 9/04/04
Source	University of Delaware
Document Type	Annual Report (Word document)
Resource Date	10/2004

Post Date	03/15/2005
Title	SOLAREX OTF ROOF SYSTEM
Link	(MS Word 96 KB)
Author	J. Adelstein
Description	This report is a quarterly update of the performance, based on the PVUSA power rating system, of the Solarex 1.2 kWac a-Si system being monitored at NREL. The system has been monitored over the 4 year period from September 1999 through December 2003. The PV array consists of 36 utility grid tied Solarex MST-43MV modules plus 6 ?dummy? modules, not connected to the power grid, and is located on the roof of NREL?s Outdoor Test Facility (OTF). It faces south (+/- 5o) with a tilt angle from the horizontal equal to 40° (latitude) and is connected to the utility grid through a 2.2 kW Omnion Series 2400 inverter in bi-polar configuration.
Venue
Source	National Renewable Energy Laboratory
Document Type	Annual Report (Word document)
Resource Date	09/21/2004

Post Date	05/24/2005
Title	DEVELOPMENT OF OPTICALLY ENHANCED BACK REFLECTORS AND IMPROVED DEPOSITION PROCESSES FOR AMORPHOUS SILICON-BASED PHOTOVOLTAIC TECHNOLOGIES
Link	(PDF 815 KB) Download Acrobat Reader.
Author	S. Jones
Description	In this program, we improve the module efficiencies through development of a new optically enhanced Al/ZnO back reflector and improved i-layer deposition process. In the case of the back reflector development, a multi-layered thin film structure consisting of films with contrasting indices of refraction placed between the Al and ZnO layers of the back reflector is developed to improve the reflectivity of the back reflector structure. The ultimate goal is to achieve the high currents and cell efficiencies typically obtained with the Ag/ZnO back reflector with a new optically enhanced back reflector that can be used in the solar module products. Ag/ZnO back reflectors are presently used only in R&D applications due to long term instabilities related to electromigration of Ag. For the multi-layered structure, focus will be on preparing the layers using sputtering techniques so that this technology might be quickly applied to ECD?s present back reflector fabrication process that uses sputtering techniques. In the case of the i-layer, focus is on preparing microcrystalline silicon based intrinsic layers for low cost, high stable efficiency solar cells through the use of high intensity (decomposition rate) plasmas. In these studies, the effects of such deposition conditions as ion bombardment, substrate temperature and etchant gases on the grain size and film transparency are studied and correlated with cell performance.
Venue	Subcontract ZDJ-2-30630-22, Annual phase 2 report
Source	Energy Conversion Devices
Document Type	Annual Report (Adobe Postscript file)
Resource Date	06/16/2004

Post Date	02/09/2005
Title	DEVELOPMENT OF OPTICALLY ENHANCED BACK REFLECTORS AND IMPROVED DEPOSITION PROCESSES FOR AMORPHOUS SILICON-BASED PHOTOVOLTAIC TECHNOLOGIES
Link	(PDF 844 KB) Download Acrobat Reader.
Author	S. Jones
Description	In this program we plan to improve the module efficiencies through development of a new optically enhanced Al/ZnO back reflector and improved i-layer deposition process. In the case of the back reflector development, a multi-layered thin film structure consisting of films with contrasting indices of refraction placed between the Al and ZnO layers of the back reflector will be developed to improve the reflectivity of the back reflector structure. The ultimate goal is to achieve the high currents and cell efficiencies typically obtained with the Ag/ZnO back reflector with a new optically enhanced back reflector that can be used in the solar module products. Ag/ZnO back reflectors are presently used only in R&D applications due to long term instabilities related to electromigration of Ag. For the multi-layered structure, focus will be on preparing the layers using sputtering techniques so that this technology might be quickly applied to ECD's present back reflector fabrication process that uses sputtering techniques. In the case of the i-layer, focus will be on preparing microcrystalline silicon based intrinsic layers for low cost, high stable efficiency solar cells through the use of high intensity (decomposition rate) plasmas. In these studies, the effects of such deposition conditions as ion bombardment, substrate temperature and etchant gases on the grain size and film transparency will be studied and correlated with cell performance. Achievement of the goals of this program and application of these advancements to ECD's joint venture company's production lines would lead to an immediate improvement in module efficiencies. These advances along with ECD's participation in the NREL a-Si teams with other development programs will contribute to the ultimate goal of achieving stable efficiencies of 15% using a low-cost, scalable, manufacturable techniques and inexpensive substrates.
Venue	NREL Subcontract
Source	Energy Conversion Devices
Document Type	Annual Report (Adobe Postscript file)
Resource Date	06/15/2004

Post Date	03/25/2005
Title	HIGH-EFFICIENCY AMORPHOUS SILICON ALLOY BASED SOLAR CELLS AND MODULES
Link	(PDF 1.9 MB) Download Acrobat Reader.
Authors	S. Guha, J. Yang
Description	The principal objective of this R&D program is to expand, enhance, and accelerate knowledge and capabilities for development of high efficiency hydrogenated amorphous silicon (a-Si:H) and amorphous silicon-germanium alloy (a-SiGe:H) related thin film multi-junction solar cells and modules with low manufacturing cost and high reliability. Our strategy has been to use the spectrum-splitting triple-junction structure, a-Si:H/a-SiGe:H/a-SiGe:H, to improve solar cell and module efficiency, stability, and throughput of production. The methodology used to achieve the objectives included: i) explore the highest stable efficiency using the triple-junction structure deposited using RF glow discharge at a low rate, ii) fabricate the devices at a high deposition rate for high throughput and low cost, and iii) develop optimized recipe using the R&D batch large-area reactor to help the design and optimization of the production roll-to-roll machines. In the last few years, the research on hydrogenated nanocrystalline silicon (nc-Si:H) solar cells has attracted significant attention in Japan and Europe. Using nc-Si:H as the bottom cell in multi-junction structures, cell efficiency of over 14% and module efficiency of over 13% have been reported. We have been exploring the use of nc-Si:H as an intrinsic layer of the bottom cell in the triple-junction solar cell to achieve higher stable cell and module efficiency. During the past year, we have worked on developing high efficiency nc-Si:H single-junction solar cells and high efficiency multi-junction solar cells using nc-Si:H as the intrinsic layer of the bottom cell. We have achieved an initial active-area efficiency of 14.6% using an a-Si:H/a-SiGe:H/nc-Si:H triple-junction structure.
Venue	Annual Technical Progress Report June 1, 2003 through May 31, 2004 ZDJ-2-30630-19
Source	Uni-Solar Ovonic
Document Type	Annual Report (Adobe Postscript file)
Resource Date	06/2004

Post Date	03/22/2005
Title	TRANSPORT, INTERFACES, AND MODELING IN AMORPHOUS SILICON BASED SOLAR CELLS
Link	(MS Word 5.3 MB)
Author	E. A. Schiff
Description	Amorphous Silicon Solar Cell Characteristics and Modeling Hole Drift Mobility Measurements in Microcrystalline and Amorphous SiliconHole-Conducting Polymers as P-layer Materials for Amorphous and Crystal Silicon Solar Cells
Venue	NREL Subcontract NDJ-2-30630-24 with Syracuse University
Source	Syracuse University
Document Type	Annual Report (Word document)
Resource Date	05/11/2004

Post Date	02/18/2005
Title	HIGH EFFICIENCY NARROW GAP AND TANDEM JUNCTION DEVICES
Link	(PDF 368 KB) Download Acrobat Reader.
Author	V. L. Dalal
Description	During this first year, we have concentrated on the following tasks. 1. Study of growth chemistry, device physics and defect densities in nanocrystalline Si solar cells for use as low bandgap cells in tandem cell structures. 2. Study of properties of a-Ge:H materials and devices for use as low bandgap cells in tandem cell structures.
Venue	Subcontract XDJ-2-30630-32, Iowa State University
Source	Iowa State University
Document Type	Annual Report (Adobe Postscript file)
Resource Date	03/15/2004

Post Date	03/25/2005
Title	OPTIMIZATION OF PHASE-ENGINEERED A-SI:H-BASED MULTI-JUNCTION SOLAR CELLS
Link	(PDF 1.5 MB) Download Acrobat Reader.
Authors	C. Wronski, et al.
Description	Materials research and device development Device loss mechanisms Characterization strategies for advanced materials
Venue	Center for Thin Film Devices The Pennsylvania State University University Park, PA 16802 Second Annual Technical Status Report January 2003 ? January 2004 Subcontract No. NDJ-1-30630-01
Source	Pennsylvania State University
Document Type	Annual Report (Adobe Postscript file)
Resource Date	02/2004

Post Date	03/15/2005
Title	STRUCTURE OF SILICON-BASED THIN FILM SOLAR CELL MATERIALS
Link	(PDF 3.9 MB) Download Acrobat Reader.
Author	D. L. Williamson
Description
Venue	Annual Technical Progress Report 1 April 2002?31 August 2003 NREL/SR-520-35227
Source	Colorado School of Mines, Golden, CO
Document Type	Annual Report (Adobe Postscript file)
Resource Date	01/2004

Post Date	03/25/2005
Title	IDENTIFYING ELECTRONIC PROPERTIES RELEVANT TO IMPROVING THE PERFORMANCE AND STABILITY OF AMORPHOUS SILICON BASED PHOTOVOLTAIC CELLS
Link	(PDF 915 KB) Download Acrobat Reader.
Authors	T. J. Anderson, J. D. Cohen
Description	We have focused primarily upon the characterization of hydrogenated nanocrystalline Si (nc-Si:H) produced at United Solar Ovonics Corporation. In addition, we examined a couple of amorphous germanium (a-Ge:H) samples produced by the ECR method at Iowa State University. Our studies of the ECR a-Ge:H confirmed the superior electronic properties of the Iowa State a-Ge:H material, both in terms of the DLCP deduced defect densities, and the TPC deduced Urbach energies. In our studies of the USOC nc-Si:H samples we found DLCP state densities in the 1015 to 1016 cm-3 range. Very little temperature dependence was observed, indicating that the majority of these are shallow donor-like states. For all 3 samples studied we observed that the DLCP densities increased in the direction of film growth. This is consistent with observations at USOC that the crystallinity size increases as the films become thicker. Our transient photocapacitance measurements disclosed a sub-band-gap spectrum that evolved from a very µc-Si:H appearance at lower temperatures (200K), to a very a-Si:H like in appearance at moderate temperatures (300K). We believe this change in appearance results from improving hole carrier collection as the temperature is increased which then diminishes the photocapacitance response of the nc-Si:H component in these materials. However, the hole carrier collection remains relatively poor in the a-Si:H component in these nc-Si:H samples so that the TPC signal in that component thus becomes dominant in the higher temperature regime even though its volume fraction is undoubtedly fairly small. Thus, our TPC method allows us to examine the electronic properties of both components in these mixed phase materials. Finally, we have begun to examine the effects of light-induced degradation in these nc-Si:H materials. The DLCP measurements actually showed very little change with light soaking, even after 100 hours at 100mW/cm2
Venue	Annual Subcontract Report 27 November 2002- 26 November 2003 ADJ-2-30630-17
Source	University of Oregon
Document Type	Annual Report (Adobe Postscript file)
Resource Date	11/2003

Post Date	04/22/2005
Title	THE MICROSCOPIC MECHANISMS OF THE STAEBLER-WRONSKI EFFECT IN A-SI FILMS AND HIGH-EFFICIENCY SOLAR CELLS
Link	(MS Word 496 KB)
Author	D. Han
Description	We studied 125 intrinsic Si films by HW-CVD on Corning 1737 glass. All of the films were grown at the same substrate temperature, Ts = 240oC. There were four groups with various silane flow rates of 3, 8, 16, and 22 sccm, respectively. The hydrogen flow rate for each group was varied from 0 to 216 sccm. Micro-Raman is an effective tool for detecting nano-grains and providing their distribution information. We present the micro-Raman date on the mixed-phase solar cells, which correlated well the structural non-uniformity to the physical model of light-induced increase of Voc observed in the mixed-phase solar cells. Single-junction n-i-p solar cells were deposited by United Solar onto 4 cm x 4 cm stainless steel (ss) substrates using a conventional rf glow discharge technique. For HW a-Si:H samples, we have observed the decreases in the FF of the solar cells and the dramatic changes in the dark conductivity for the i-layer regarding the various gases and thermal cycles. Three effects could be involved in the changes that are: surface adsorption, oxygen incorporation and thermal relaxation. We observed that the surface adsorption of H2O in the air resulted in a great rising of the dark conductivity discharge technique. Indium-tin-oxide (ITO) dots of area 0.25 cm2 were deposited on the p layer as the top contact.
Venue	subcontract ADJ-1-30630-09, Phase II Annual report
Source	University of North Carolina, Chapel Hill
Document Type	Annual Report (Word document)
Resource Date	10/31/2003

Post Date	02/02/2005
Title	2003 DOE PV PEER REVIEW
Link	(PDF 716 KB) Download Acrobat Reader.
Author	N/A
Description	Review of DOE PV activities in 2003
Venue	US DOE EERE
Source	US DOE
Document Type	Annual Report (Adobe Postscript file)
Resource Date	09/30/2003

Post Date	02/09/2005
Title	DEVELOPMENT OF OPTICALLY ENHANCED BACK REFLECTORS AND IMPROVED DEPOSITION PROCESSES FOR AMORPHOUS SILICON-BASED PHOTOVOLTAIC TECHNOLOGIES
Link	(MS Word 787 KB)
Authors	S. Jones, et al.
Description	In this program, we plan to improve the module efficiencies through development of a new optically enhanced Al/ZnO back reflector and improved i-layer deposition process. In the case of the back reflector development, a multi-layered thin film structure consisting of films with contrasting indices of refraction placed between the Al and ZnO layers of the back reflector will be developed to improve the reflectivity of the back reflector structure. The ultimate goal is to achieve the high currents and cell efficiencies typically obtained with the Ag/ZnO back reflector with a new optically enhanced back reflector that can be used in the solar module products. Ag/ZnO back reflectors are presently used only in R&D applications due to long term instabilities related to electromigration of Ag. For the multi-layered structure, focus will be on preparing the layers using sputtering techniques so that this technology might be quickly applied to ECD's present back reflector fabrication process that uses sputtering techniques. In the case of the i-layer, focus will be on preparing microcrystalline silicon based intrinsic layers for low cost, high stable efficiency solar cells through the use of high intensity (decomposition rate) plasmas. In these studies, the effects of such deposition conditions as ion bombardment, substrate temperature and etchant gases on the grain size and film transparency will be studied and correlated with cell performance. Achievement of the goals of this program and application of these advancements to ECD's joint venture company's production lines would lead to an immediate improvement in module efficiencies. These advances along with ECD's participation in the NREL a-Si teams with other development programs will contribute to the ultimate goal of achieving stable efficiencies of 15% using a low-cost, scalable, manufacturable techniques and inexpensive substrates.
Venue	NREL Subcontract
Source	Energy Conversion Devices
Document Type	Annual Report (Word document)
Resource Date	09/15/2003

Post Date	02/09/2005
Title	PROCESSING MATERIALS, DEVICES AND DIAGNOSTICS FOR THIN FILM PHOTOVOLTAICS: FUNDAMENTAL AND MANUFACTURABILITY ISSUES
Link	(MS Word 4.6 MB)
Authors	R. W. Birkmire, S. S. Hegedus, B. E. McCandless, W. N. Shafarman, et al.
Description
Venue	Annual report ADJ-1-30630-12
Source	University of Delaware
Document Type	Annual Report (Word document)
Resource Date	09/04/2003

Post Date	03/25/2005
Title	HIGH EFFICIENCY AND HIGH RATE DEPOSITED AMORPHOUS SILICON-BASED SOLAR CELLS
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Author	X. Deng
Description	High-Efficiency Single-Junction a-SiGe Solar Cells Section 3 Optimization of High-efficiency a-Si Top Cell Section 4 Amorphous Silicon Deposited Using Trisilane as Precursor Section 5 Deposition of a-SiGe:H and nc-SiGe:H films using HWCVD
Venue	PHASE II Annual Technical Progress Report September 1, 2002 to August 31, 2003 NREL Subcontract No. NDJ-2-30630-08
Source	University of Toledo
Document Type	Annual Report (Adobe Postscript file)
Resource Date	09/2003

Post Date	03/04/2005
Title	PROCESSING MATERIALS, DEVICES AND DIAGNOSTICS FOR THIN FILM PHOTOVOLTAICS: FUNDAMENTAL AND MANUFACTURABILITY ISSUES
Link	(MS Word 4.5 MB)
Author	R. W. Birkmire
Description
Venue	ADJ-1-30630-12 9/05/02 to 9/04/03
Source	University of Delaware
Document Type	Annual Report (Word document)
Resource Date	09/2003

Post Date	03/03/2005
Title	PROCESSING, MATERIALS, DEVICES AND DIAGNOSTICS FOR THIN-FILM PHOTOVOLTAICS: FUNDAMENTAL AND MANUFACTURABILITY ISSUES
Link	(MS Word 37 KB)
Author	R. W. Birkmire
Description
Venue	PV Program Contract Summary Report Thin-film PV Partnership Program
Source	University of Delaware
Document Type	Annual Report (Word document)
Resource Date	09/2003

Post Date	03/22/2005
Title	MEASUREMENT OF DEPOSITING AND BOMBARDING SPECIES INVOLVED IN THE PLASMA PRODUCTION OF AMORPHOUS SILICON AND SILICON/GERMANIUM SOLAR CELLS
Link	(MS Word 3.0 MB)
Authors	A. Gallagher, et al.
Description	The technical approach to this project is to utilize mass spectrometry to measure radical and ion species that arrive at the substrate of a plasma-enhanced-chemical-vapor-deposition (PECVD) reactor. A small-scale reactor mimics those used to produce hydrogenated amorphous (a-Si:H) and microcrystalline (mc-Si) silicon and silicon/germanium (a-Si:Ge:H) solar cells. Radio frequency (RF) and high frequency (HF) discharges will normally be studied, and the reactor utilizes a similar electrode gap (2-3 cm), substrate temperature (20-250 °C), gas pressures (0.1-5 Torr), gas mixtures and discharge power density to that used in an industrial reactor.
Venue	Subcontract
Source	University of Colorado, Boulder
Document Type	Annual Report (Word document)
Resource Date	08/31/2003

Post Date	03/25/2005
Title	HIGH-EFFICIENCY AMORPHOUS SILICON ALLOY BASED SOLAR CELLS AND MODULES
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Authors	S. Guha, J. Yang
Description	The principal objective of this R&D program is to expand, enhance, and accelerate knowledge and capabilities for development of high efficiency hydrogenated amorphous silicon (a-Si:H) and amorphous silicon-germanium alloy (a-SiGe:H) related thin film multi-junction solar cells and modules with low manufacturing cost and high reliability. Our strategy has been to use the spectrum-splitting triple-junction structure, a-Si:H/a-SiGe:H/a-SiGe:H, to improve solar cell and module efficiency, stability, and throughput of production. The methodology used to achieve the objectives was: i) explore the highest stable efficiency using the triple-junction structure deposited using RF glow discharge at a low rate, ii) fabricate the devices at a high deposition rate for high throughput and low cost, and iii) develop optimized recipe using the R&D batch large-area reactor to help the design of the production roll-to-roll machines. In the last few years, research on microcrystalline silicon (?c-Si:H) solar cells has attracted significant attention in Japan and Europe. Using ?c-Si:H as the bottom cell in multi-junction structures, cell efficiency over 14% and module efficiency over 13% have been reported. We have been exploring the use of ?c-Si:H as an intrinsic layer of the bottom cell in the triple-junction solar cell to achieve higher stable cell and module efficiency. During the past year, we have worked on developing high efficiency ?c-Si:H single-junction solar cell and high efficiency multi-junction solar cells based on ?
Venue	ZDJ-2-30630-19 Annual Technical Progress Report May 30, 2002 through May 31, 2003
Source	Uni-Solar Ovonic
Document Type	Annual Report (Adobe Postscript file)
Resource Date	06/2003

Post Date	03/25/2005
Title	HIGH-EFFICIENCY AMORPHOUS SILICON ALLOY BASED SOLAR CELLS AND MODULES
Link	(PDF 1.5 MB) Download Acrobat Reader.
Authors	S. Guha, J. Yang
Description	The principal objective of this R&D program is to expand, enhance, and accelerate knowledge and capabilities for development of high efficiency hydrogenated amorphous silicon (a-Si:H) and amorphous silicon-germanium alloy (a-SiGe:H) related thin film multi-junction solar cells and modules with low manufacturing cost and high reliability. Our strategy has been to use the spectrum-splitting triple-junction structure, a-Si:H/a-SiGe:H/a-SiGe:H, to improve solar cell and module efficiency, stability, and throughput of production. The methodology used to achieve the objectives was: i) explore the highest stable efficiency using the triple-junction structure deposited using RF glow discharge at a low rate, ii) fabricate the devices at a high deposition rate for high throughput and low cost, and iii) develop optimized recipe using the R&D batch large-area reactor to help the design of the production roll-to-roll machines. In the last few years, research on microcrystalline silicon (?c-Si:H) solar cells has attracted significant attention in Japan and Europe. Using ?c-Si:H as the bottom cell in multi-junction structures, cell efficiency over 14% and module efficiency over 13% have been reported. We have been exploring the use of ?c-Si:H as an intrinsic layer of the bottom cell in the triple-junction solar cell to achieve higher stable cell and module efficiency. During the past year, we have worked on developing high efficiency ?c-Si:H single-junction solar cell and high efficiency multi-junction solar cells based on ?
Venue	Annual Technical Progress Report May 30, 2002 through May 31, 2003 ZDJ-2-30630-19
Source	Uni-Solar Ovonic
Document Type	Annual Report (Adobe Postscript file)
Resource Date	06/2003

Post Date	02/08/2005
Title	THIN FILM SILICON CELLS ON LOW-COST SUBSTRATES
Link	(PDF 363 KB) Download Acrobat Reader.
Author	H. A. Atwater
Description	2002 Annual Technical Report to the Midwest Research Institute National Renewable Energy Laboratory Subcontract DE-AC36-99GO10337 "Thin Film Silicon Cells on Low-Cost Substrates" Contract Performance Period 7/11/02-7/10/05.
Venue	NREL Subcontract
Source	California Institute of Technology
Document Type	Annual Report (Adobe Postscript file)
Resource Date	12/31/2002

Post Date	03/22/2005
Title	IDENTIFYING ELECTRONIC PROPERTIES RELEVANT TO IMPROVING THE PERFORMANCE AND STABILITY OF AMORPHOUS SILICON BASED PHOTOVOLTAIC CELLS
Link	(PDF 1.1 MB) Download Acrobat Reader.
Author	J. D. Cohen
Description	Amorphous silicon
Venue	Annual Subcontract Report 27 November 2001- 26 November 2002 ADJ-2-30630-17 NREL Technical Monitor: B. von Roedern
Source	University of Oregon
Document Type	Annual Report (Adobe Postscript file)
Resource Date	12/2002

Post Date	04/27/2009
Title	PROCESSING MATERIALS DEVICES AND DIAGNOSTICS FOR THIN FILM PHOTOVOLTAICS: FUNDAMENTAL AND MANUFACTURABILITY ISSUES
Link	(PDF 1.6 MB) Download Acrobat Reader.
Authors	R. W. Birkmire, W. N. Shafarman, E. Eser, S. S. Hegedus, B. E. McCandless, K. D. Dobson, S. Bowden
Description	This report describes results achieved under this subcontract to develop and understand thin-film solar cell technology associated to CuInSe2 and related alloys, a-Si and its alloys, and CdTe. This includes application of a-Si to c-Si wafer-type cells, as well. Modules based on all these thin films are promising candidates to meet DOE long-range efficiency, reliability, and manufacturing cost goals. The critical issues being addressed under this program are intended to provide the science and engineering basis for developing viable commercial processes and to improve module performance. The generic research issues addressed are: 1) quantitative analysis of processing steps to provide information for efficient commercial-scale equipment design and operation; 2) device characterization relating the device performance to materials properties and process conditions; 3) development of alloy materials with different bandgaps to allow improved device structures for stability and compatibility with module design; 4) development of improved window/heterojunction layers and contacts to improve device performance and reliability; and 5) evaluation of cell stability with respect to illumination, temperature, and ambient and with respect to device structure and module encapsulation.
Venue	Institute of Energy Conversion (IEC), University of Delaware, subcontract ADJ-1-30630-12, Final Report
Source	University of Delaware
Document Type	Final Report (Adobe Postscript file)
Resource Date	04/2009

Post Date	05/27/2008
Title	HIGH-EFFICIENCY AMORPHOUS SILICON AND NANOCRYSTALLINE SILICON-BASED SOLAR CELLS AND MODULES
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Authors	S. Guha, J. Yang
Description	United Solar Ovonic LLC successfully used its spectrum-splitting a-Si:H/a-SiGe:H/a-SiGe:H triple-junction structure in their manufacturing plants, achieving manufacturing capacity of 118 MW in 2007 from its Auburn Hills and Greenville, Michigan plants. United Solar has a very aggressive expansion plan to achieve grid parity by improving its solar panel efficiency, improving manufacturing throughput, and reducing manufacturing cost. In the Thin Film Partnership Program, Uni-Solar identified three areas of research: i) Optimize a-Si:H and a-SiGe:H deposition parameters under the current manufacturing constraints for improving solar module efficiency and manufacturing throughput, and reducing the manufacturing cost; ii) Explore new deposition methods for a-Si:H and a-SiGe:H materials to improve a-Si:H/a-SiGe:H/a-SiGe:H triple-junction cell efficiency at high deposition rates; and iii) Explore new materials and new cell structures for higher efficiency at high deposition rates.
Venue	United Solar Ovonic LLC, subcontract ZXL-6-44205-14, Final Report
Source	Uni-Solar Ovonic
Document Type	Final Report (Adobe Postscript file)
Resource Date	05/2008

Post Date	10/04/2006
Title	OPTIMIZATION OF PHASE-ENGINEERED A-SI:H-BASED MULTI-JUNCTION SOLAR CELLS
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Authors	C. Wronski, R. W. Collins, N. Podraza, J. Pearce, G. Ferreira, C. Chen
Description	The scope of the work under this subcontract has involved investigating engineered improvements in the performance and stability of solar cells in a systematic way, which included the following four tasks: 1. Materials research and device development; 2. Process improvement directed by real time diagnostics; 3. Device loss mechanisms; and 4. Characterization strategies for advanced materials. Our work has resulted in new and important insights into the deposition of a-Si:H-based materials, as well as into the nature of the Staebler-Wronski Effect (SWE). Presumably, many of these insights will be used by industrial partners to develop more systematic approaches in optimizing solar cells for higher performance and stability. This effort also cleared up several serious misconceptions about the nature of the p-layer in cells and the SWE in materials and cells. Finally, the subcontract identified future directions that should be pursued for greater understanding and improvement.
Venue	Pennsylvania State University, Subcontract NDJ-1-30630-01, Final Report
Source	Pennsylvania State University
Document Type	Final Report (Adobe Postscript file)
Resource Date	08/2006

Post Date	06/29/2006
Title	MEASUREMENT OF DEPOSITING AND BOMBARDING SPECIES INVOLVED IN THE PLASMA PRODUCTION OF AMORPHOUS SILICON AND SILICON/GERMANIUM SOLAR CELLS
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Author	A. Gallagher
Description	The present observations of SiHn and Si2Hn radical densities at a-Si:H and ?c-Si substrate surfaces indicate that SiH3 is the most abundant radical, but significant amounts of Si2H2 also occur. Other smaller density components such as SiH and Si2H4 occur for a pure silane discharge, but are below detection limits for the R = 16 and 36 discharges. Since SiH3 is relatively inefficient at depositing Si into the film, these other radicals could provide a significant (> 10%) contribution to film growth, and thereby also to device properties. The radical density that should vary the most with R (hydrogen dilution) is, of course, the H atom. Our current data is ambiguous regarding H atom densities, so we do not report these preliminary results here. There is a strong indication that H densities at the substrate vary with surface condition as well as with R, but this still has to be verified.
Venue	DE-AC36-02GO10244 agreement with NIST (and CU) Boulder, Final Report
Source	NIST
Document Type	Final Report (Adobe Postscript file)
Resource Date	06/2006

Post Date	02/01/2006
Title	HIGH EFFICIENCY AND HIGH RATE DEPOSITED AMORPHOUS SILICON-BASED SOLAR CELLS
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Author	X. Deng
Description	This final report covers the research works on the Project ?High Efficiency and High-Rate Deposited Amorphous Silicon-Based Solar Cells? at the University of Toledo for the Period of September 1, 2001 to March 06, 2005, under NREL Subcontract No. NDJ-2- 30630-08. The objectives of this project are (1) to establish a transferable knowledge and technology base for the fabrication of high-efficiency triple-junction a-Si-based solar cells and (2) to develop high-rate deposition techniques for the growth of a-Si-based and related alloys including poly-Si, µc-Si, a-SiGe and a-Si films and photovoltaic devices with these materials.
Venue	Final Report, subcontract NDJ-2-30630-08, University of Toledo
Source	University of Toledo
Document Type	Final Report (Adobe Postscript file)
Resource Date	12/19/2005

Post Date	11/17/2005
Title	IDENTIFYING ELECTRONIC PROPERTIES RELEVANT TO IMPROVING THE PERFORMANCE AND STABILITY OF AMORPHOUS SILICON BASED PHOTOVOLTAIC CELLS
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Author	J. D. Cohen
Description	We used DLCP and transient photocapacitance (TPC) spectroscopy to characterize the electronic properties of hydrogenated nanocrystalline Si (nc-Si:H) produced at United Solar Ovonics Corporation. We found DLCP state densities in the 10^15 to 10^16 cm^-3 range and found for the three samples deposited under constant hydrogen dilution that these increased in the direction of film growth. This is consistent with observations at Uni-Solar that the crystallite size increases as the films become thicker, and this also leads to an increase in deep defect density. However, one sample deposited using hydrogen profiling showed a very different spatial distribution of these defects, as well as lower densities overall. Our transient photocapacitance measurements disclosed a sub-band-gap spectrum that evolved from a very µc-Si:H appearance at lower temperatures (200K), to a very a-Si:H like in appearance at moderate temperatures (300K). By comparing TPC with transient photocurrent (TPI) spectra we demonstrated that this change in appearance results from improving hole carrier collection as the temperature is increased which then diminishes the photocapacitance response of the nanocrystalline component in these materials relative to the a-Si:H component in these mixed phase samples. We also examined the effects of light-induced degradation in some detail for one of the nc-Si:H samples. The DLCP measurements actually showed very little change with light soaking, even after 100 hours at 100mW/cm^2. However, significant degradation in the hole carrier collection were observed in the TPC measurements, by nearly a factor of 50 at most temperatures. However, we did not observe any increase in any spectral feature, including the dangling bond defect band, that might be responsible for the observed loss in hole collection. Work continued to try to identify the fundamental reasons that higher growth rate a-Si:H materials lead to devices with generally lower performance. Previously, our measurements had revealed that the deep defect density determined by drive-level capacitance profiling (DLCP) did not change as the growth rate was varied; however, the Urbach energies deduced by transient photocapacitance (TPC) sub-band-gap spectroscopy were correlated with growth rate and hence also the device performance. During the current Subcontract we found that the magnitudes of the deep defect revealed in the TPC spectra also correlated quite well with the device fill factors, even though the DLCP determined defect densities did not. Thus we now suggest that the capture cross section of the deep defects are enhanced at the higher growth rates even though their actual density do not vary substantially. We also report results on a new series of samples, part of a five-way collaboration with NREL, Colorado School of Mines, University of North Carolina, and BP Solar. Results for this new series of samples agreed with the previous set in that the DLCP determined defect densities appeared to be largely uncorrelated with device performance, while the Urbach energies were strongly correlated. The other studies of the collaboration revealed that the void fraction and the hydrogen content were also quite strongly correlated with growth rate. Once again, the cell performance exhibited a systematic decline in performance with increasing growth rate.
Venue	Subcontract ADJ-2-30630-17, final report, NREL/SR-520-38676
Source	University of Oregon
Document Type	Final Report (Adobe Postscript file)
Resource Date	11/2005

Post Date	11/17/2005
Title	CHARACTERIZATION OF AMORPHOUS SILICON ADVANCED MATERIALS AND PV DEVICES
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Author	P. C. Taylor
Description	We have emphasized two approaches that are unique to the research group at Utah. First, we have used novel electron paramagnetic (or spin) resonance (ESR) and nuclear magnetic resonance (NMR) techniques, such as measurements of silicon dangling bonds using second harmonic detection of ESR and measurements of the spin-lattice relaxation in a dipolar field (T1D) or in a rotating frame (T1?) to probe the influence of paramagnetic silicon dangling bonds in doped and intrinsic a-Si:H and selected alloys. Second, we have used below-gap optical spectroscopy [photoluminescence (PL), PL excitation (PLE), ESR, optical absorption, optically detected magnetic resonance (ODMR), etc.] with a tunable Ti sapphire laser system to excite carriers at energies that extend from above the optical gap to well below the gap (down to ~ 0.1 eV). We have also performed more standard experiments, such as photothermal deflection spectroscopy (PDS) and the constant photocurrent method (CPM). The most significant results of the three phases of the sub-contract are (1) the discovery of a paired hydrogen site in light-soaked a-Si:H that is probably the stabilization mechanism for the silicon dangling bonds created in the Staebler-Wronski effect, (2) the confirmation of universal kinetics for the decay of optically excited electrons and holes in a-Si:H and a-Ge:H at low temperatures, (3) the first detection of the Staebler-Wronski effect in a-Ge:H, (4) the use of a novel decay of tritium in a-Si:H to probe the production of silicon dangling-bond defects, and (5) the comparison of ESR and CPM measurements of defects in a-Si:H material used in cells.
Venue	Subcontract ADJ-2-30630-23, University of Utah, final report, NREL/SR-520-38678
Source	University of Utah
Document Type	Final Report (Adobe Postscript file)
Resource Date	11/2005

Post Date	10/27/2005
Title	HIGH-EFFICIENCY AMORPHOUS SILICON ALLOY BASED SOLAR CELLS AND MODULES
Link	(PDF 2.6 MB) Download Acrobat Reader.
Authors	S. Guha, J. Yang
Description	The principal objective of this R&D program is to expand, enhance, and accelerate knowledge and capabilities for development of high-efficiency hydrogenated amorphous silicon (a-Si:H) and amorphous silicon-germanium alloy (a-SiGe:H) related thin-film multi-junction solar cells and modules with low manufacturing cost and high reliability. Our strategy has been to use the spectrum-splitting triple-junction structure, a-Si:H/a-SiGe:H/a-SiGe:H, to improve solar cell and module efficiency, stability, and throughput of production. The methodology used to achieve the objectives included: i) explore the highest stable efficiency using the triple-junction structure deposited using RF glow discharge at a low rate, ii) fabricate the devices at a high deposition rate for high throughput and low cost, and iii) develop an optimized recipes using the R&D batch large-area reactor to help the design and optimization of the roll-to-roll production machines. For short-term goals, we have worked on the improvement of a-Si:H and a-SiGe:H alloy solar cells. a-Si:H and a-SiGe:H are the foundation of current a-Si:H based thin film photovoltaic technology. For long-term goals, we have explored alternative materials and advanced technologies for next generation thin-film photovoltaic production. We investigated the possibility of using nc-Si:H as the bottom cell in a-Si:H/nc-Si:H double-junction and a-Si:H/a-SiGe:H/nc-Si:H triple-junction structures to address the long term goals for the next generation large volume and low cost manufacturing plants. Three issues have been identified as the main focus in this study: i) searching for the highest stable cell and module efficiency; ii) increasing deposition rate and reducing deposition time to satisfy manufacturing requirements, and iii) investigating the issues related to large-area deposition, especially the uniformity of layer thickness and cell performance. We accumulated significant experience in material deposition and characterization, solar cell design and manufacture, and device characterization. We have achieved initial active-area efficiencies of 13.5% and 14.6% using a-Si:H/nc-Si:H double-junction and a-Si:H/a-SiGe:H/nc-Si:H triple-junction structures, respectively.
Venue	subcontract ZDJ-2-30630-19, Final Report, NREL/SR-520-38728, United Solar Ovonics Corporation
Source	Uni-Solar Ovonic
Document Type	Final Report (Adobe Postscript file)
Resource Date	10/2005

Post Date	05/05/2006
Title	THIN FILM SILICON CELLS ON LOW-COST SUBSTRATES
Link	(MS Word 982 KB)
Author	H. A. Atwater
Description	The overall project goal was to synthesize polycrystalline Si thin films for thin film solar cells at low temperature (T oC) on low-cost (e.g., glass) substrates. This understanding was be used to delineate the path to break through existing barriers to high-rate synthesis of high-quality thin films for polycrystalline silicon photovoltaics applications. In this context, high quality refers to large grain size (> film thickness) and long (> film thickness) minority carrier diffusion length. The program in Tasks I and II was successful against these goals; Task III was cancelled by NREL.
Venue	Subcontract XDJ-2-30630-25, California Institute of Technology, Final Report
Source	California Institute of Technology
Document Type	Final Report (Word document)
Resource Date	06/01/2005

Post Date	07/19/2005
Title	MICROSCOPIC MECHANISM OF THE STAEBLER-WRONSKI EFFECT IN MAY 2005 A-SI FILMS AND HIGH-EFFICIENCY SOLAR CELLS
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Author	D. Han
Description	In high growth rate (? 50 Å/s) HW-CVD a-Si:H films, for the first time, we show gaseous molecules in nanovoids (~2% volume fraction of tube-like nanoscale voids), and demonstrate that confinement on the nanometer scale generates NMR effects that have never been observed in macroscopic systems. In the same system we found the PL peak red shift. We suggest that highly strained bonds on the inner surfaces of the nanoscale voids form broad conduction-band tail states that are responsible for the PL red shift. We characterized the structural transition from a- to nc-Si as function of H-dilution, thickness and Ts of both HW- and PE-CVD films using IR, Raman, PL, CPM/PDS and Ea. We found not only the c-Si volume fraction but also the grain boundaries (g.b.) and microstructures play an important role in the properties of the i-layer and their solar cell performance. We found a narrow structural transition zone in which the bond-angle variation decreases from 10? to 8?. For nc-Si samples, we found a characteristic low energy PL peak and proved that is originated from the g.b. regions. Using micro-Raman, direct evidence is provided of the structural non-uniformity that causes the light-induced Voc enhancement in mixed-phase solar cells.
Venue	University of North Carolina, subcontract ADJ-1-30630-09, Final Report
Source	University of North Carolina, Chapel Hill
Document Type	Final Report (Adobe Postscript file)
Resource Date	05/2005

Post Date	05/11/2005
Title	HIGH EFFICIENCY NARROW GAP AND TANDEM JUNCTION DEVICES
Link	(PDF 737 KB) Download Acrobat Reader.
Author	A. Madan
Description	The work reported in this report uses a modified pulsed PECVD technique which has been successfully developed to fabricate state of the art nc-Si materials and devices. Specifically we have achieved the following specific benchmarks. 1. nc-Si:H device with an efficiency of 8% achieved at a deposition rate of ~1A/s. 2. nc-Si:H device with an efficiency of 7% achieved at a depostion rate of ~5A/s. 3. Large-area technology developed using pulsed PECVD with uniformity of +/-5% over 25cm x 35cm. 4. An innovative stable four terminal (4-T) tandem junction device of ?>9% fabricated. ( It should be noted that the 4-T device fabricated with existing technology base and with further development can reach stabilized ? of 12%). 5. With improvement in Voc ~ 650 mV, from the current value of 480mV, 4-T device with ?>16% would be possible. Towards this objective, modified pulsed PECVD was developed where layer by layer modification of nc-Si:H has been achieved. It should be noted that the due to budget cuts at NREL, this project was curtailed by about one year.)
Venue	Subcontract ZDJ-2-30630-31, Final Report
Source	MVSystems
Document Type	Final Report (Adobe Postscript file)
Resource Date	03/2005

Post Date	01/03/2006
Title	ENERGY PAY-BACK AND LIFE CYCLE CO2 EMISSIONS OF THE BOS IN AN OPTIMIZED 3.5 MW PV INSTALLATION
Link	tepbos2005
Author	J. Mason
Description	This study is a life-cycle analysis of the balance of system (BOS) components of the 3.5 MWp multi-crystalline PV installation at Tucson Electric Power's (TEP) Springerville, AZ field PV plant. TEP instituted an innovative PV installation program guided by design optimization and cost minimization. The advanced design of the PV structure incorporated the weight of the PV modules as support, thereby eliminating the need for concrete foundations. The estimate of the life-cycle energy requirements embodied in the BOS is 543 MJ/m2, a 71% reduction from those of an older central plant; the corresponding life-cycle greenhouse gas emissions are 29 kg CO2-eq. /m2. From field measurements, the energy payback time (EPT) of the BOS is 0.21 years for the actual location of this plant, and 0.37 years for average US insolation/temperature conditions. This is a great improvement from the EPT of 2 years estimated for an older central plant. The total cost of the balance of system components was $940 US per kWp of installed PV, another milestone in improvement. These results were verified with data from different databases and further tested with sensitivity- and data-uncertainty analyses. Key Words: PV plant; balance of system; life cycle assessment, energy payback, GHG emissions
Venue	website
Source	Tucson Electric
Document Type	Final Report (Hypertext link)
Resource Date	2005

Post Date	04/21/2005
Title	PVACCEPT
Link	PVACCEPT
Author	N/A
Description	PVACCEPT is a German-Italian research project, which was funded by the European Commission within the programme "Innovation and Small and Medium Sized Enterprises". The project aimed at designing and developing marketable solar modules for electricity generation, which are designed in a way to enable their sensitive and inconspicuous integration into old buildings, historical sites, and protected landscapes. The project has officially started on 1st July 2001, and is concluded since 31st December 2004.
Venue
Sources	University of Arts, Berlin; University of Siena
Document Type	Final Report (Hypertext link)
Resource Date	12/2004

Post Date	05/12/2005
Title	DEVELOPMENT OF ADVANCED DEPOSITION TECHNOLOGY FOR MICROCRYSTALLINE SI BASED SOLAR CELLS AND MODULES
Link	(PDF 1.9 MB) Download Acrobat Reader.
Author	Y. Li
Description	The objectives of this project, covering the first two phases of an originally anticipated three-phase undertaking, are the development of novel deposition techniques for microcrystalline silicon materials (µc-Si, which is now more appropriately called nanocrystalline Si or nc-Si), and the demonstrations of solar cells with nc-Si absorbers, in single junction and tandem structures, of high efficiencies produced by low-cost, high-throughput, single chamber PECVD method. We have achieved the technical goals set for the end of this project (Phase II), which were: i) nc-Si single junction solar cells of 6% efficiency; ii) a-Si/nc-Si tandem solar cells of 8% post-lightsoaking efficiency; iii) nc-Si films produced by HWCVD (at Syracuse University which focused on nc-Si material preparation). The efficiency values confirmed by NREL are 6.5% and 8.7%, respectively, for nc-Si single junction and a-Si/nc-Si tandem solar cells, produced with ?near-the edge? nc-Si absorbers using mediocre ZnO/Al back contacts. Our nc-Si devices exhibit excellent stability in ambient or under light exposure, and typically show a slight increase in conversion efficiency after long-term illumination. The a-Si/nc-Si tandem solar cells show more notable degradation (~10-15%) under one-sun light soaking than 47-sun accelerated exposure (< 8%). The most critical element in device processing has been found to be the seeding procedure by which nc-Si absorber (the i-layer) is grown over an amorphous-Si based under-layer or directly on a TCO front contact. We have conducted an extensive search for the best seeding techniques, including i-layer seeding and the novel ?closed chamber? seeding methods. Seeding by boron-doped p-layer, preferably on a ZnO-coated SnO2, has resulted in superior nc-Si cells. Other highly challenging issues, such as dopant and impurity contamination, reproducibility, and tunnel junction performance for the a-Si/nc-Si tandem cells have been successfully addressed. We have also explored new TCOs in light-trapping structures for advanced optical engineering of devices. We have established correlations between microstructure and device performance of the nc-Si materials. High-efficiency and high crystallinity of the i-layer are mutually exclusive in nc-Si solar cells.
Venue	subcontract ZDJ-2-30630-28, final report
Source	Energy Photovoltaics
Document Type	Final Report (Adobe Postscript file)
Resource Date	12/2004

Post Date	02/04/2005
Title	STUDY OF POTENTIAL COST REDUCTIONS RESULTING FROM SUPER-LARGE-SCALE MANUFACTURING OF PV MODULES
Link	(PDF 768 KB) Download Acrobat Reader.
Authors	R. Arya, M. Keshner, K. Zweibel
Description	Technology investments by the U.S. government Dept. of Energy, National Renewable Energy Lab (NREL) and others over the past 30 years have positioned the Solar Energy industry to undergo an inflection. The technology is now very close to good enough. The key issue is cost.
Venue	NREL final report NREL/SR-520-36846 Subcontract No. ADJ-3-33631-01
Sources	Hewlett Packard; National Renewable Energy Laboratory
Document Type	Final Report (Adobe Postscript file)
Resource Date	10/2004

Post Date	03/11/2005
Title	LEARNING FROM THE SUN
Link	(PDF 3.3 MB) Download Acrobat Reader.
Authors	E. A. Alsema, G. J. Schaeffer, et al.
Description	Analysis of the use of experience curves for energy policy purposes: The case of photovoltaic power. Final report of the Photex project
Venue	ECN-C--04-035
Source	Photex
Document Type	Final Report (Adobe Postscript file)
Resource Date	08/2004

Post Date	02/11/2005
Title	WORKSHOP ON LIFE CYCLE ANALYSIS AND RECYCLING OF SOLAR MODULES - THE "WASTE" CHALLENGE
Link	(PDF 12.5 MB) Download Acrobat Reader.
Author	A. Jager-Waldau
Description	First, to rise the awareness of the Photovoltaic Community about the European Directives 2002/96/EC on waste electrical and electronic equipment (WEEE) and 2002/95/EC on the restriction of the use of certain hazardous substances in electrical and electronic equipment (ROHS), which have to be implemented by the Member States in 2004. These directives will have a significant impact on the PV industry, not only because the future waste classification of PV modules is an important issue, but also the sustainability and the green image of the PV industry as a whole has to be considered. The second focus was on Life Cycle Assessment the correct evaluation of External Costs and the Recycling of Solar Modules, which will help to avoid these problems. The workshop gave an overview about the current scientific and political discussion, identified problems and showed the way for possible solutions.
Venue	European Commission EUR 21101 EN
Source	European Commission Joint Research Centre
Document Type	Final Report (Adobe Postscript file)
Resource Date	03/19/2004

Post Date	02/07/2005
Title	PV STATUS REPORT 2003
Link	(PDF 671 KB) Download Acrobat Reader.
Author	A. Jager-Waldau
Description	Research, Solar Cell Production and Market Implementation in Japan, USA and the European Union.
Venue	European Commission JRC EUR 20850EN
Source	Institute for Environment and Sustainability
Document Type	Final Report (Adobe Postscript file)
Resource Date	09/2003

Post Date	03/15/2005
Title	OPTIMIZATION OF PHASE-ENGINEERED A-SI:H-BASED MULTI-JUNCTION SOLAR CELLS
Link	(PDF 1.5 MB) Download Acrobat Reader.
Authors	C. Wronski, et al.
Description	Task 1. Materials research and devices Task 2. Process improvement directed by real time diagnostics Task 3. Device loss mechanisms Task 4. Characterization strategies for advanced materials
Venue	Final Technical Status Report January 2002 ? April 2003 Subcontract No. NDJ-1-30630-01
Source	Pennsylvania State University
Document Type	Final Report (Adobe Postscript file)
Resource Date	04/2003

Post Date	03/07/2005
Title	USE OF VERY HIGH FREQUENCY PLASMAS TO PREPARE A-SI:H BASED TRIPLE-JUNCTION SOLAR CELLS AT HIGH DEPOSITION RATES
Link	(MS Word 3.5 MB)
Authors	S. Jones, et al.
Description	The main objective of this program is to develop a high rate, amorphous silicon-based, thin film deposition method in order to increase the throughput of ECD's roll-to-roll solar module production design and in doing so reduce the cost of the solar modules. In particular, a very high frequency (VHF) [70 MHz] plasma enhanced chemical vapor deposition (PECVD) process is being developed for the fabrication of intrinsic layers for high efficiency amorphous silicon-based triple-junction solar cells at high deposition rates. Intrinsic layers consisting of either amorphous silicon or amorphous silicon germanium alloy materials are being developed. The program goal is to prepare these materials at rates of 10 Å/s or higher while maintaining the cell efficiencies at the high values presently obtained for devices made using the standard 13.56 MHz frequency and low deposition rates (near 1 Å/s). Upon completion of a successful program, this high rate process will be added to ECD's roll-to-roll solar cell production design to reduce solar module cost.
Venue	Subcontract Report
Source	Energy Conversion Devices
Document Type	Final Report (Word document)
Resource Date	08/10/2001

Post Date	03/22/2005
Title	HIGH EFFICIENCY TRIPLE-JUNCTION AMORPHOUS SILICON ALLOY PHOTOVOLTAIC TECHNOLOGY
Link	(MS Word 4.7 MB)
Author	S. Guha
Description	The principal objective of this R&D program is to expand, enhance and accelerate knowledge and capabilities for the development of high-performance, two-terminal multijunction hydrogenated amorphous silicon alloy cells and modules with low manufacturing cost and high reliability. The program goal is to obtain 12% stable modules that will qualify IEEE-Std 1262-1995 reliability testing.
Venue	Final Technical Report March 6, 1998 ? October 15, 2001 ZAK-8-17619-09
Source	Uni-Solar Ovonic
Document Type	Final Report (Word document)
Resource Date	2001

Post Date	02/11/2005
Title	ENVIRONMENTAL ASPECTS OF PV POWER SYSTEMS
Link	(PDF 278 KB) Download Acrobat Reader.
Authors	E. A. Alsema, E. Nieuwlaar
Description	An expert workshop was held as part of the International Energy Agency Photovoltaic Power Systems Implementing Agreement Programme, to address these environmental aspects of PV power systems. The objectives of the workshop were: Review/overview of issues and approaches regarding environmental aspects of PV power systems; Enhanced clarity and consensus regarding well-known aspects like Energy Pay-Back Time; Identification of issues of environmental importance regarding PV power systems ('hot spots'); Identification of issues requiring further attention ('white spots');
Venue	IEA PVPS Task 1 Workshop 25-27 June 1997 Utrecht, The Netherlands Report no. 97072
Source	Utrecht University
Document Type	Final Report (Adobe Postscript file)
Resource Date	12/1997

Post Date	02/11/2005
Title	ENVIRONMENTAL ASPECTS OF SOLAR CELL MODULES
Link	(PDF 466 KB) Download Acrobat Reader.
Author	E. A. Alsema
Description	multicrystalline silicon, amorphous silicon, cadmium telluride and copper indium selenide are reviewed with special attention to future expected technology developments. For each module type an assessment is made of the potential environmental impacts in case of large scale implementation of the technology. In principle the entire module life cycle is taken into consideration: from resource mining, via module production and module utilization until module decommissioning and waste handling. In the report for each module type the following aspects are discussed: energy requirements and energy pay-back time, material requirements and resource depletion, environmental emissions, waste handling, possibilities for recycling of modules, occupational health and safety and external safety.
Venue	Report nr. 96074 ISBN 90-73958-17-2 Netherlands Agency for Energy and the Environment (NOVEM)
Source	Utrecht University
Document Type	Final Report (Adobe Postscript file)
Resource Date	08/1996

Quarterly Reports

Post Date	03/13/2009
Title	INNOVATIVE CHARACTERIZATION OF AMORPHOUS AND THIN-FILM SILICON FOR IMPROVED MODULE PERFORMANCE
Link	(PDF 282 KB) Download Acrobat Reader.
Author	J. D. Cohen
Description	We have been applying junction capacitance methods to investigate the effects of Ga grading on a set of four CuIn1-xGaxSe2 (CIGS) sample devices at the National Renewable Energy Laboratory (NREL). One device was deposited with a uniform Ga depth profile (x=0.30), two were deposited so that the Ga fraction varied monotonically from near x=0.9 at the Mo back contact to either x=0.15 or x=0.25 at the junction interface, and the last device utilized a compositional variation close to NREL's optimal ?v-shaped? bandgap grading scheme. Following deposition, SIMS measurements were carried out at NREL to provide a detailed spatial map of the Ga/(Ga+In) ratios in the CIGS absorbers. One of the most revealing effects of Ga grading were obtained from our transient photocapacitance (TPC) and photocurrent (TPI) spectra. These measurements provided a spectral map of the optically induced release of carriers for photon energies from 0.6eV to 2eV. Comparing the two types of spectra enables one to distinguish majority from minority carrier processes. We also attempted to obtain additional spatial information by varying the applied DC bias to weight the spectral response to different regions relative to the barrier junction. The edge of the depletion region under different (steady-state) DC biases were estimated by the high frequency junction capacitance values. We concluded that we are really sampling regions farther from the junction.
Venue	University of Oregon, subcontract ZXL-5-44205-11, quarterly report
Source	University of Oregon
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	11/2008

Post Date	11/04/2008
Title	PROCESSING, MATERIALS, DEVICES AND DIAGNOSTICS FOR THIN FILM PHOTOVOLTAICS: FUNDAMENTAL AND MANUFACTURABILITY ISSUES
Link	(PDF 1.3 MB) Download Acrobat Reader.
Author	R. W. Birkmire
Description	The report investigates passivation of x-Si wafers using PECVD deposited a-Si:H. An interdigitated back contact-silicon heterojunction cell with efficiency of 13.5% and FF of 77% is achieved with the narrower band gap i-layer. However, the Voc and Jsc is lower than the standard i-layer, which is due to insufficient surface passivation in the gap between the p- and n- strips.
Venue	Institute of Energy Conversion, University of Delaware, subcontract ADJ-1-30630-12, monthly report
Source	University of Delaware
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	08/19/2008

Post Date	11/04/2008
Title	FABRICATION AND CHARACTERIZATION OF ADVANCED TRIPLE-JUNCTION AMORPHOUS SILICON BASED SOLAR CELLS
Link	(PDF 1.2 MB) Download Acrobat Reader.
Authors	X. Deng, R. W. Collins
Description	Nano-crystalline silicon solar cells on back-reflectors (BR) with ZnO films deposited at 120 ºC have low FF and low Jsc but high Voc. The reason of this phenomenon may be that the low temperature deposited ZnO films have less crystallinity, which causes the nano-crystalline silicon film to have more amorphous phase. But when the ZnO is deposited at high temperature (350 C), lots of ZnO crystalline rods show up, this can cause yield problems to solar cells. Based on the BR with ZnO deposited at 280 C, we have fabricated a-Si:H/a-SiGe:H/nc-Si:H n-i-p triple junction solar cells with initial efficiency of 12.5%.
Venue	University of Toledo, subcontract ZXL-5-44205-06, quarterly report
Source	University of Toledo
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	07/2008

Post Date	11/04/2008
Title	FABRICATION AND CHARACTERIZATION OF ADVANCED TRIPLE-JUNCTION AMORPHOUS SILICON BASED SOLAR CELLS
Link	(PDF 483 KB) Download Acrobat Reader.
Authors	X. Deng, R. W. Collins
Description	High efficiency single junction n-i-p type a-Si:H solar cells were fabricated, with the intrinsic layers deposited at the edge of crystallinity. The stability tends to be better with increasing the RF-power, which improves the structure order in the i-layers. Solar cells with i-layers deposited just below the onset of crystallinity show a higher initial efficiency, while solar cells with i-layers deposited just above the onset of crystallinity show a better stability against light soaking.
Venue	University of Toledo, subcontract ZXL-5-44205-06, quarterly report
Source	University of Toledo
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	07/2008

Post Date	05/01/2008
Title	PROCESSING, MATERIALS, DEVICES AND DIAGNOSTICS FOR THIN-FILM PHOTOVOLTAICS: FUNDAMENTAL AND MANUFACTURING ISSUES
Link	(PDF 404 KB) Download Acrobat Reader.
Author	R. W. Birkmire
Description	High efficiency Si solar cells require a textured surface with an anti-reflection layer, to reduce reflection and increase light trapping, and a well-passivated surface, to reduce recombination and increase VOC. The three processing sequences must be integrated together and be compatible with one another to achieve the full benefits. This section covers work performed at IEC to develop inverted pyramidal texturing on a planar (100) FZ wafer, followed by chemical cleaning of the surface and low temperature passivation. The process of inverted texturing developed at IEC is as follows: 1. PECVD deposition of 20nm SiN sacrificial layer 2. Photoresistor is applied and pattern is defined by mask 3. Patterning using photolithography 4. 60s 1:9 buffered oxide etch (BOE) etching SiN to open texturing window and exposure of Si surface 5. 30% KOH solution with 2%IPA @ 50 degrees textures surface and gets desirable pattern
Venue	Institute of Energy Conversion (IEC, U. Delaware), subcontract ADJ-1-30630-12, monthly report
Source	University of Delaware
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	04/18/2008

Post Date	04/11/2008
Title	HIGH-EFFICIENCY AMORPHOUS SILICON AND NANOCRYSTALLINE SILICON BASED SOLAR CELLS AND MODULES
Link	(PDF 120 KB) Download Acrobat Reader.
Authors	S. Guha, J. Yang
Description	Because of realignment of the Thin Film Partnership Program (TFPP) with the Solar America Initiative Program (SAI), some of the tasks in the original TFPP program were not to continued. Based on the modified statement of work, we have carried out the following activities. 1. We conducted collaboration work with the analytical group and thin film silicon group of the National Renewable Energy Laboratory and carried out a systematic study of microstructures of mixed-phase hydrogenated silicon solar cells. We have previously reported the nanocrystalline cone formation in the mixed-phase materials. In this quarter, we continued to characterize mixed-phase films made with various hydrogen dilutions using Raman spectroscopy, AFM, conductive-AFM, and X-TEM. However, the investigation has not been completed, results will be reported in the future. 2. We optimized a-Si:H top cells in the regime very close to the amorphous/nanocrystalline transition. In order to keep the material still in the amorphous phase through the entire intrinsic layer thickness, hydrogen dilution profiling was used. A high Voc of 1.055 V has been achieved in this study. 3. We continued to optimize a-SiGe:H single-junction solar cells; the a-SiGe:H with high Ge contents is important yet challenging for device optimization. In this quarter, we focused on the optimization of a-SiGe:H single-junction cells with a Voc between 0.65 V and 0.70V, which is normally used as the bottom cell in an a-Si:H/a-SiGe:H/a-SiGe:H triple-junction solar cell. 4. In order to achieve high efficiency multi-junction solar cells, we need to improve back reflectors to enhance the light trapping effect. In this quarter, we continue to optimize Ag/ZnO back reflectors and compared the a-SiGe:H solar cells made on various back reflectors. It appears that when a thin ZnO layer is used, textured Ag is needed. On the other hand, when the ZnO layer is thick enough to provide sufficient light scattering, a specular Ag layer results in an optical enhancement better than a textured Ag layer. We also carried out a study for estimating the optical enhancement in a-SiGe:H solar cells. We proposed a calculation method for the optical enhancement and found that the optimized Ag/ZnO back reflector results in an optical enhancement 20 to 30 times greater in the long wavelength region.
Venue
Source	Uni-Solar Ovonic
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	01/2008

Post Date	12/13/2007
Title	BARRIER COATINGS AND STABILITY OF THIN FILM SOLAR CELLS
Link	(PDF 51 KB) Download Acrobat Reader.
Author	L. Olsen
Description	Data were acquired for SSI mini-modules that were coated with PNNL barrier coatings based on the new polymer blend. Results were obtained for coated modules subjected to 85ºC and dry conditions, and modules with barrier coatings of thicknesses ranging from 3 microns to 10 microns. The 85ºC/Dry testing was done to determine if the coatings react in a negative way with the devices. We found that all coated modules were stable in the 85ºC/Dry conditions. Figure 3 gives results for a module with a coating 10 microns thick. Basically, the module is stable. Thus, it is very clear that the SSI mini-module can tolerate 85ºC and dry conditions, but not a stress of 86ºC/85%RH. Figure 4 gives results for coated mini-modules with the results for a bare module shown for contrast. Although the PNNL barrier coatings have made a tremendous difference, degradation still occurs. The fact that all modules degrade at the same rate, regardless of coating thickness, provides an important clue as to the cause of the degradation. Based on our overall experience, the effectiveness of the barrier coatings should improve with thickness. In general, we find that there are three cell features that can lead to defects in the multi-layer coatings which in turn provide a path for water diffusion: (i) Surface roughness; (ii ) Inadequate edge seal; (iii) Cuts separating individual cells. Since the rate of degradation of efficiency is independent of the coating thickness, we suspect that features (ii) and (iii) are most likely responsible for causing pathways of moisture diffusion. Further studies are required before this problem(s) can be clearly identified. However, the results achieved with the new polymer blends in an 85/85 environment are very encouraging.
Venue	Pacific Northwest National Laboratory, subcontract DAX-4-44239-01, quarterly report
Source	Pacific Northwest National Lab (PNNL)
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	12/01/2007

Post Date	01/04/2008
Title	PROCESSING, MATERIALS, DEVICES AND DIAGNOSTICS FOR THIN FILM PHOTOVOLTAICS: FUNDAMENTAL AND MANUFACTURABILITY ISSUES
Link	(PDF 196 KB) Download Acrobat Reader.
Author	R. W. Birkmire
Description	An interdigitated back contact silicon heterojunction solar cell is discussed, which combines the high voltage potential of heterojunction solar cells while avoiding the absorption losses in these structures which allowing high short circuit currents. This structure has interdigitated p/n amorphous silicon (a-Si:H) films deposited by low temperature plasma enhanced chemical vapor deposition on the backside of crystalline silicon (c-Si) wafers, with the light irradiating the front surface. The device is attractive for manufacturing due to the all back contact design, the large tolerances in dimensions, low temperature of depositions, and the lack of shunting. Initial solar cells have open circuit voltages of 691 mV but low fill factors. Two-dimensional modeling is used to explain the present low fill factors and demonstrate that the structure allows efficiencies in excess of 24%. The work resulted in four papers presented at the 22nd European Photovoltaic Solar Energy Conference and Exhibition.
Venue	Institute for Energy Conversion, University of Delaware, subcontract ADJ-1-30630-12, monthly report
Source	University of Delaware
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	10/23/2007

Post Date	01/03/2008
Title	PROCESSING, MATERIALS, DEVICES AND DIAGNOSTICS FOR THIN FILM PHOTOVOLTAICS: FUNDAMENTAL AND MANUFACTURABILITY ISSUES
Link	(PDF 34 KB) Download Acrobat Reader.
Author	R. W. Birkmire
Description	Si surface passivation quality of undoped Si:H layer was compared by depositing Si:H layers using RF and DC plasma process and on Si (100) and Si (111) Fz wafers. Plasma process of Si:H layer has only a weak dependence on surface passivation quality. Wafer orientation was demonstrated to have a large effect on passivation quality of Si:H layers. The measured lifetime clearly exhibit a pronounced Si wafer orientation. Cell Efficiency of ~ 16% was achieved on polished n-type Fz (100) wafers with VOC ~680mV using both RF and DC plasma deposited a-Si:H i- layers. NREL confirmed efficiency of 11.8% was achieved in an interdigitated back contact Si heterojunction cells, without any i- layer passivation in the rear and thus low VOC of 600 mV. Incorporation of i- layer passiva tion in the rear improves cell VOC and JSC but results in ?S? shape J-V with low FF. The increase in JSC is due to excellent passivation in the gap of p- and n- strips and high VOC of > 680 mV is due to efficient passivation by i- layer in the emitter and contact strip.
Venue	Institute of Energy Conversion, U. Delaware, subcontract ADJ-1-30630-12, quarterly report
Source	University of Delaware
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	10/23/2007

Post Date	10/25/2007
Title	INNOVATIVE CHARACTERIZATION OF AMORPHOUS AND THIN-FILM SILICON FOR IMPROVED MODULE PERFORMANCE
Link	(PDF 73 KB) Download Acrobat Reader.
Author	N/A
Description	We have shown that the defect densities of two tritiated amorphous silicon samples at 77 K increase linearly in time up to 10^19cm^-3. The final densities, however, are factors of 4 to 8 smaller than the density of tritium atoms that have decayed. From NMR experiments, we know that 3 at. % of the atoms in the sample exists as hydrogen in the dilute phase and the rest is in the clustered phase. Therefore, some of the clustered tritium atoms probably do not produce silicon dangling bonds at 77 K due to reconstruction. There is no evidence of saturation at 77 K. These results provide further hints for the role of hydrogen in creating defects in light soaked samples at low temperature.
Venue	University of Utah, Subcontract No. XXL-5-44205-09, quarterly report
Source	University of Utah
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	10/2007

Post Date	10/25/2007
Title	INNOVATIVE CHARACTERIZATION OF AMORPHOUS AND THIN-FILM SILICON FOR IMPROVED MODULE PERFORMANCE
Link	(PDF 99 KB) Download Acrobat Reader.
Author	P. C. Taylor
Description	We have performed ESR measurements in H-effused a-Si:H thin films made by both HWCVD and PECVD. The evolution of the defect density as a function of annealing time is consistent with that found in optical measurements. Analysis of the line-width shows that in H-effused states, the defects are either clustered or exist in pairs. A simple model of the exchange interaction in a-Si can account for the difference in line shapes observed in these films as compared to a-Si:HT samples described in a previous status report. In addition to our studies on hydrogen doublets with United Solar Ovonics, we are continuing our collaborative studies on tritiated samples with NREL. Also, we are continuing our irradiation of device quality samples of a-Si:H at 77 K for long periods of time to test for saturation.
Venue	University of Utah, Subcontract No. XXL-5-44205-09, quarterly report
Source	University of Utah
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	10/2007

Post Date	08/10/2007
Title	FABRICATION AND CHARACTERIZATION OF ADVANCED TRIPLE-JUNCTION AMORPHOUS SILICON BASED SOLAR CELLS
Link	(PDF 605 KB) Download Acrobat Reader.
Authors	X. Deng, R. W. Collins
Description	Section 1: Executive Summary Section 2: Deposition Phase Diagram and Correlation with the Performance of a-Si:H Thin Film Solar Cells Section 3: Origin of optical losses in Ag/ZnO back-reflectors for thin film Si photovoltaics
Venue	University of Toledo, subcontract ZXL-5-44205-06 (a-Si), quarterly report
Source	University of Toledo
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	08/2007

Post Date	08/10/2007
Title	FABRICATION AND CHARACTERIZATION OF ADVANCED TRIPLE-JUNCTION AMORPHOUS SILICON BASED SOLAR CELLS
Link	(PDF 470 KB) Download Acrobat Reader.
Authors	X. Deng, R. W. Collins
Description	Section 1: Executive Summary Section 2: 8% nc-Si solar cells deposited over 30 ?/s rate using VHF-PECVD with high pressure high power regime Section 3: High deposition rate a-Si(Ge):H solar cells made by VHF-PECVD Section 4: Surface Roughness and Phase Evolution of Si:H and Si1-xGex
Venue	University of Toledo, subcontract ZXL-5-44205-06 (a-Si), quarterly report
Source	University of Toledo
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	08/2007

Post Date	09/18/2007
Title	FABRICATION AND CHARACTERIZATION OF ADVANCED TRIPLE-JUNCTION AMORPHOUS SILICON BASED SOLAR CELLS
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Authors	X. Deng, R. W. Collins
Description	Using a Si:H deposition phase diagram as guidance, we have fabricated and optimized high performance single-junction a-Si:H n-i-p solar cells with 8 Å/s intrinsic layers of protocrystalline Si:H materials. We have found that the Voc values of the solar cells with i-layers made near the protocrystalline regime are very sensitive to the hydrogen dilution ratioR=[H2]/[Si2H6]. An initial efficiency of ? = 9.99% was obtained for the cell with improved protocrystalline silicon material evolved at the i/p interface region. The light-induced stability in efficiemncy is also improved using protocrystalline materials. Deposition phase diagrams have been developed and augmented for vhf PECVD of thin film Si:H and its alloys with Ge by incorporating contour lines representing the crystalline fraction in the top ~10 Å of the i-layer at a given bulk layer thickness. These diagrams predict optimum one-step i-layer deposition processes for the top and middle cells of a triple-junction device that are in consistency with the performance of single-junction devices.
Venue	University of Toledo, subcontract ZXL-5-44205-06, quarterly report
Source	University of Toledo
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	07/2007

Post Date	09/18/2007
Title	FABRICATION AND CHARACTERIZATION OF ADVANCED TRIPLE-JUNCTION AMORPHOUS SILICON BASED SOLAR CELLS
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Authors	X. Deng, R. W. Collins
Description	We have established a database of a-Si(1-x)Ge(x):H dielectricspectra as a function of Ge content x. This dielectric function database was then applied to the analysis of a compositionally graded a-Si(1-x)Ge(x) thin film, where a four medium virtual interface analysis was used to extract the surface roughness evolution, instantaneous growth rate, and Ge content x as functions of time or alternatively as functions of bulk layer thickness (or depth from the substrate interface). The relationships between x and the various Cody-Lorentz energyindependent dielectric function parameters also make it possible to extract any of those parameters as functions of time or depth once the value of x is known. Optical simulations have been performed to investigate the effect of Ag/ZnO interface layers in back-reflectors for thin film triple junction a-Si:H solar cells in the n-i-p configuration. The role of interface layers generated by differing amounts of initial Ag surface roughness has been explored. It has been observed that increasing the initial surface roughness of Ag increases the losses through absorption in the interlayer. As expected, increasing the interface thickness for a given interface layer dielectric function enhances the absorption losses in the interlayer. The goal of the back-reflector fabrication studies is to identify the origins of the interface losses and eliminate them through modifications in the back-reflector design. Modeling studies such as these supplement the experimental work and predict the improvements that may be expected.
Venue	University of Toledo, subcontract ZXL-5-44205-06, quarterly report
Source	University of Toledo
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	07/2007

Post Date	05/24/2007
Title	HIGH-EFFICIENCY AMORPHOUS SILICON AND NANOCRYSTALLINE SILICON BASED SOLAR CELLS AND MODULES
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Authors	S. Guha, J. Yang
Description	We have worked on many areas of improving the a-Si:H, a-SiGe:H, and nc-Si:H based multi-junction solar cell efficiency and optimized the different elements of the mutli-junction solar cells. The major focuses were high rate deposition of nc-Si:H solar cells with MVHF glow discharge and large-area uniformity deposition of nc-Si:H solar cells. We have carried out the optimization of different hydrogen dilution profiles and tried to correlate the deposition process with material properties and solar cell performance. The characterization work has been carried out at the University of Oregon and NREL. However, the full characterization has not been finished. We will report the results when it is complete. We have worked on the optimization of Ag/ZnO. Through the collaboration with NREL, we have systematically characterized the Ag/ZnO structures and correlated the surface roughness to solar cell performance. We have studied the electrical bias effect on the stability of a-Si:H/nc-Si:H double-junction solar cells. We found that the a-Si:H/nc-Si:H double-junction solar cells with a bottom cell limited current mismatch showed a higher light-induced degradation under the short-circuit condition than the open circuit condition. This observation is consistent with the previously observed bias dependence of light-induced degradation in nc-Si:H single-junction cells. We have worked on the large-area nc-Si:H solar cells and tried to improve the uniformity and efficiency. Based on the manufacturing requirements, we have worked on the nc-Si:H deposition using a moderate spacing between the cathode and the substrate to reduce the complicity of manufacturing machine design. Currently, we have achieved a module efficiency similar to that made with a smaller gap spacing.
Venue	United Solar Ovonic Corp., subcontract ZXL-6-44205-14, quarterly report
Source	Uni-Solar Ovonic
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	05/2007

Post Date	03/16/2007
Title	PROCESSING, MATERIALS, DEVICES AND DIAGNOSTICS FOR THIN FILM PHOTOVOLTAICS: FUNDAMENTAL AND MANUFACTURABILITY ISSUES
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Author	R. W. Birkmire
Description	Photolithography is the most flexible approach to implement proof-of-concept rear junction cells. It allows a relatively straightforward method to explore process variations while maintaining control over the process sequence. The goal of using the photolithographic approaches is to demonstrate the feasibility of rear junction solar cells and to develop an understanding of the dominant physical processes. The results indicate the potential of the basic device concept being investigated at IEC. Increased VOC can be expected with optimization of the passivation (there was no intrinsic a-Si layer between the silicon and a-Si doped layer) and increased JSC with a more transparent front passivation layer and AR coating. NREL confirmed the following data on a 1.32 cm^2-area cell: Voc = 602 mV, Jsc = 26.7 mA/cm^2, FF = 73.3%, efficiency = 11.8%.
Venue	IEC, University of Delaware, subcontract ADJ-1-30630-12, monthly report
Source	University of Delaware
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	02/01/2007

Post Date	03/09/2007
Title	PROCESSING, MATERIALS, DEVICES AND DIAGNOSTICS FOR THIN FILM PHOTOVOLTAICS: FUNDAMENTAL AND MANUFACTURABILITY ISSUES
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Author	R. W. Birkmire
Description	One of the key aspects of high efficiency silicon heterojunction (SHJ) solar cells (>21%) is the reduction of surface recombination by minimizing structural and electronic defects at the interface between amorphous silicon (a-Si:H) and crystalline silicon (c-Si). Excellent surface passivation and high lifetime (> 1 msec) can be achieved by both RF and DC plasma process with hydrogen dilution. Any epitaxial growth of the i-layer reduces minority carrier lifetime dramatically. The structure of thin Si:H layer depend on the orientation of single crystalline Si. Undesirable epitaxial growth of Si:H films is more likely to occur on Si (100) compared to (111) surface. The lower VOC in SHJ cells for i-layers having epitaxial or mixed phase growth observed in literature is due to loss in surface passivation quality by Si:H layers.
Venue	Institute of Energy Conversion (IEC), University of Delaware, subcontract ADJ-1-30630-12, monthly report
Source	University of Delaware
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	01/25/2007

Post Date	12/23/2005
Title	INNOVATIVE CHARACTERIZATION OF AMORPHOUS AND THIN-FILM SILICON FOR IMPROVED MODULE PERFORMANCE
Link	(MS Word 100 KB)
Author	P. C. Taylor
Description	We present results on two samples, deposited by plasma-enhanced chemical vapor deposition (PECVD) from SiH4 and tritium gas mixtures. The first sample was grown at a substrate temperature of 225 oC. This sample is similar to those used in devices, in which the initial defect densities are the lowest experimentally obtainable (film thickness of 0.26 ?m). The second sample was grown at 150 oC. This sample, which is representative of a more defective material (film thickness of 1.5 ?m), showed considerable dihydride bonding (silicon bonded to two Si and two H atoms) as measured by Fourier transform infrared (FTIR) spectroscopy. Because of the presence of silicon-tritium bonds, one expects the tritium decay to accumulate Si dangling bond defects after the samples have been deposited. The density of these defects should follow approximately the number of decayed tritium atoms per unit volume. Since our first measurements were made seven years after deposition, the density of decayed tritium was about 6x1020 cm-3 or a few at. %. Surprisingly, both electron spin resonance (ESR) measurements of the neutral silicon dangling bond density and photothermal deflection spectroscopy (PDS) measurements of the absorption of both neutral and charged defects yielded densities that were lower by about 3 orders of magnitude (5 x 10^17 cm^-3 and 4 x 10^17cm^-3 for films deposited at 150 oC and 225 oC, respectively). In addition, most of these defects annealed at temperatures between about 150 and 200 oC with kinetics similar to that observed for the optically induced defects created in the Staebler-Wronski effect.
Venue	University of Utah, subcontract XXL-5-44205-09, 3rd quarterly report
Source	University of Utah
Document Type	Quarterly Report (Word document)
Resource Date	12/22/2006

Post Date	12/06/2006
Title	INNOVATIVE CHARACTERIZATION OF AMORPHOUS AND THIN-FILM SILICON FOR IMPROVED MODULE PERFORMANCE
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Author	J. D. Cohen
Description	The primary results to be reported from work in my laboratory during this period have come from continuing studies carried out by my post-doc, Shouvik Datta, on a series of four a-Si,Ge:H samples with roughly 29at.% Ge that were deposited with controlled varying levels of oxygen. These samples were grown by the HWCVD method at NREL and received by us in February 2006. The NREL a-Si,Ge:H samples were co-deposited onto both specular stainless steel and p+ crystalline Si substrates. Subsequent SIMS analysis indicated oxygen concentrations in the four films deposited with leak rates of (A) 0 (B) 0.02 sccm, (C) 0.06 sccm, and (D) 0.2 sccm were 8 × 10^18, 3 × 10^19, 1 × 10^20, and 5 × 10^20 cm-3, respectively. Semitransparent Pd Schottky contacts were evaporated onto both types of samples. However, for the films deposited onto c-Si we utilized the buried junction at the substrate for our capacitance based characterization measurements. A light-soaked state of both samples was examined after exposure to 610nm filtered light from an ELH source for 100hours at an intensity of 1W/cm2. The role of the additional defect band is even more apparent in the spectra of the light soaked state of the 0.06sccm air-leak sample. Here we find that it has a similar or perhaps even a slightly smaller magnitude than for State A. The defect band at EC ? 0.85eV, on the other hand, was found to increase, but only by a factor of about 1.5. The same factor increase was found for DLCP data obtained before and after light-soaking of this sample. (The Urbach energy used to obtain the fits to the spectra in the light-soaked state was again 47meV.) Somewhat surprisingly the hole/electron collection fraction appears now to have increased (to above 98%).
Venue	U. of Oregon, Subcontract ZXL-5-44205-11, quarterly report
Source	University of Oregon
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	12/01/2006

Post Date	12/06/2006
Title	HIGH-EFFICIENCY AMORPHOUS SILICON AND NANOCRYSTALLINE SILICON BASED SOLAR CELLS AND MODULES
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Authors	S. Guha, J. Yang
Description	The effects of the intrinsic and i/p buffer layer thicknesses on nc-Si:H cell performance and stability have been studied. The results show that the i/p buffer layer not only has a large effect on cell performance, but also on the stability. For the cells with a thin intrinsic layer, the cell performance, especially Voc, is limited by the i/p interface. An optimized i/p buffer layer can improve the cell performance significantly. For the thick cells, the cell performance is limited by the bulk properties of the intrinsic layer. In this case, the buffer layer effect becomes less obvious. We also found that the stability dependence on intrinsic layer thickness for nc-Si:H cells is different from a-Si:H cells. The results were explained in terms of different contributions from the bulk properties of the intrinsic layer and the i/p interface layer. We have optimized the a-SiGe:H component cells at high deposition rates on SS substrate. An active-area Pmax of 4.4 mW/cm^2 has been achieved under AM1.5 with a 530 nm cut-on filter. By combining this cell with an optimized high rate a-Si:H top cell, we have made an a-Si:H/a-SiGe:H double-junction cell on Ag/ZnO coated SS with an initial active-area efficiency of 11.7%.
Venue	United Solar Ovonic Corporation, Subcontract ZXL-6-44205-14, quarterly report
Source	Uni-Solar Ovonic
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	11/28/2006

Post Date	10/11/2006
Title	PROCESSING, MATERIALS, DEVICES AND DIAGNOSTICS FOR THIN FILM PHOTOVOLTAICS: FUNDAMENTAL AND MANUFACTURABILITY ISSUES
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Author	R. W. Birkmire
Description	Incorporation of heavily doped p+ large grain seed layers by AIC (Aluminum induced crystallization) were evaluated using different structures. Two different kinds of absorber layers (i-type mc-Si & p-type mc-Si) and two different emitter layers (n-type a-Si & n-type mc-Si) are used. Both absorber layers and emitter layers will be deposited by HWCVD. Here, we report the status of that work and also other experiments.
Venue	IEC, U. Delaware, subcontract ADJ-1-30630-12, monthly report
Source	University of Delaware
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	10/03/2006

Post Date	08/22/2006
Title	HIGH-EFFICIENCY AMORPHOUS SILICON AND NANOCRYSTALLINE SILICON BASED SOLAR CELLS AND MODULES
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Authors	S. Guha, J. Yang
Description	We have found that the MVHF-deposited a-Si:H solar cells showed good initial efficiency and stability. The most important result is that the cell performance and stability do not depend on the deposition rate up to 14 Å/s. This phenomenon is quite different from the cells made using RF at high rates. The degradation rate of the RF-cells usually increases with the deposition rate.
Venue	United Solar Ovonic Corp., Subcontract ZXL-6-44205-14, quarterly report
Source	Uni-Solar Ovonic
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	08/18/2006

Post Date	08/17/2006
Title	FABRICATION AND CHARACTERIZATION OF ADVANCED TRIPLE-JUNCTION AMORPHOUS SILICON BASED SOLAR CELLS
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Authors	X. Deng, R. W. Collins
Description	For nanocrystalline Silicon Bottom Cell using VHF PECVD technique, new deposition regimes have been developed in our UT multi-chamber load-locked PECVD deposition system at deposition rates in the range of 2-15 Å/s. Incorporating various improvements in device fabrication and characterization, 7.8% initial and 7.4% stable active-area (0.25 cm2) cell efficiencies have been achieved for VHF nc-Si n-i-p single-junction solar cells. Using a nc-Si:H cell as component bottom-cell, 12.4% initial and 11% stable cell efficiencies in a-Si/a-SiGe/nc-Si triple-junction structure have also been achieved. a-Si1-xGex:H films have been prepared by rf PECVD on the cathode (Vb ~ 20 V) in order to track the effects of increased Ge concentration and H2-dilution on film microstructural evolution and predicted material characteristics. Through such studies, it is shown that the R value at which the amorphous-to-mixed phase transition occurs for the desired device thickness increases with increasing x. Optimum alloy fabrication just before the amorphous-to-mixed phase transition for the given thickness is demonstrated through the minimum stable surface roughness and the maximum amorphous roughening transition for materials with optical (Tauc) band gaps from 1.85 to 1.35 eV and below. A simple depiction is provided detailing the continuous improvements in material properties accessible by increasing R to the mixed-phase boundary.
Venue	University of Toledo, subcontract ZXL-5-44205-06, quarterly report.
Source	University of Toledo
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	08/09/2006

Post Date	08/17/2006
Title	FABRICATION AND CHARACTERIZATION OF ADVANCED TRIPLE-JUNCTION AMORPHOUS SILICON BASED SOLAR CELLS
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Authors	X. Deng, R. W. Collins
Description	Our work focused on the optimization of ZnO as a part of back reflector(BR) for nano-crystalline (nc-Si:H) and amorphous silicon (a-SiGe:H) thin film solar cells. The effect of deposition temperature of ZnO on film morphology and as a part of BR on the performance of nc-Si:H solar cell has been analyzed. We have found that the nano-crystalline silicon solar cells on BRs with ZnO films deposited at 120ºC have low FF and low Jsc but high Voc. The reason of this phenomenon may be that the low temperature deposited ZnO film causes the nano-crystalline silicon film to have more amorphous phase. But when the ZnO is deposited at high temperature (350ºC), lots of crystallite rods show up, this can cause shunting problem to the solar cells. Based on the BR with ZnO deposited at 280ºC, we have fabricated a-Si:H / a-SiGe:H /nc-Si:H n-i-p triple junction solar cells with efficiency of 12.5%. For an improved understanding of optical losses in Ag/ZnO back-reflectors for thin film Si photovoltaics we have analyzed the structural evolution of the Ag film as well as interface formation with ZnO by real time spectroscopic ellipsometry (RTSE). We start by depositing a Ag film that exhibits the minimum surface roughness in order to determine interface optical losses under a best-case scenario, then controlled microscopic roughness on the Ag to assess differences in the optical losses while remaining within the specular regime. To study the optics of back-reflectors used in Si-based thin film solar cells, previously ultrasmooth layers of Ag were prepared, ZnO was overdeposited, and the losses that occur in this ideal situation were characterized. In the present study, the optical structure of the real Ag/ZnO interface, including microscopic roughness and macroscopic roughness (i.e., texture, roughness on the scale of the wavelength) is analyzed using a laminar film model. The intent of this work is to understand and quantify the losses in the full range of Ag/ZnO structures from the ideal to the fully textured.
Venue	University of Toledo, subcontract ZXL-5-44205-06, quarterly report
Source	University of Toledo
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	08/09/2006

Post Date	08/17/2006
Title	FABRICATION AND CHARACTERIZATION OF ADVANCED TRIPLE-JUNCTION AMORPHOUS SILICON BASED SOLAR CELLS
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Author	X. Deng
Description	We present the effect of applying DC external bias voltage to the substrate during preparation of a nanocrystalline silicon solar cell. The deposition rate, grain size, orientation property is found to be independent of the bias conditions, whereas the crystal volume fraction shows drastic change by varying bias value. This modification results in cell performance variations. A positive bias of 20 V exhibits the highest efficiency of 7.7%, while further positive bias and any negative bias produces lower efficiencies than the one made at zero bias (~6.0%). Even if we adjust the crystal volume fraction so as to obtain 50% which is done by changing hydrogen dilution ratio for several bias condition, a bias of +20V leads to the maximum efficiency, suggesting that the appropriate positive bias value (~+20 V) is effective in improving nc-Si:H solar cell performances. The effect of hydrogen dilution grading on preparation of nanocrystalline silicon (nc-Si:H) intrinsic layer has been studied in the present work. Using hydrogen dilution grading, nc-Si:H single junction solar cells have been fabricated at a high deposition rate 8 Å/s with considerable high spectral response in longer wavelengths. The same grading in R has lead to different structural properties at the p/i interface with the present choices of final values of R. A requirement of proper coupling of grading with thickness is evident from the present study. Triple junction a-Si/a-SiGe:H/nc-Si:H cells have been fabricated using the nc-Si:H signle junctions in the present study and a conversion efficiency of 11.2% is achieved. The Jsc of triple junction cells are shown to be limited by that of the nc-Si:H bottom components and remarkable improvement in FF is noticed in triple junction cells compared to the same in the corresponding nc-Si:H single junctions. Using spectroscopic ellipsometry, evaluation of crystalline volume fraction at different level of growth is undergoing, which will enable fine-tuning of grading in hydrogen dilution to tackle p/i interface properties. Using Very-high-frequency (VHF) PECVD technique with a frequency of 70 MHz, device-quality a-SiGe i-layers were prepared by using gas source of Si2H6 and GeH4 mixture at a high deposition rate of ~10 Å/sec. Film uniformity was studied with different processing pressures, which revealed that relative good homogeneous films on a 10 x 10 cm2 sample was preferred to be grown at low pressure (~0.45 Torr). The Si/Ge ratio and hydrogen dilution are the two main factors for the optimization of a-SiGe:H i-layer quality. Incorporating the optimum a-SiGe i-layer, an initial active-area (0.25 cm2) cell efficiency of 8.6% (Voc=0.612 V. Jsc=21.64 mA/cm2, FF=0.65) has been achieved for a narrow bandgap a-SiGe:H n-i-p single-junction structure. The efficiency is reduced by 13% after 100 hours of light soaking.
Venue	University of Toledo, Subcontract ZXL-5-44205-06, quarterly report
Source	University of Toledo
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	08/09/2006

Post Date	07/21/2006
Title	PROCESSING, MATERIALS, DEVICES, AND DIAGNOSTICS FOR THIN FILM PHOTOVOLTAICS: FUNDAMENTAL AND MANUFACTURABILITITY ISSUES
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Authors	R. W. Birkmire, U. Das, M. Lu
Description	Results are reported on preparation and annealing (RTP) methods for the fabrication of thin crystalline Si films using Al-induced crystallization and solid phase crystallization
Venue	Subcontract ADJ-1-30630-12, IEC, quarterly report
Source	University of Delaware
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	07/19/2006

Post Date	07/25/2006
Title	INNOVATIVE CHARACTERIZATION OF AMORPHOUS AND THIN-FILM SILICON FOR IMPROVED MODULE PERFORMANCE
Link	(MS Word 135 KB)
Author	P. C. Taylor
Description	We have continued collaborations with United Solar Ovonics Corporation on defects that contribute to the Staebler-Wronski effect in modules made using a-Si:H and a-SixGe1-x:H intrinsic layers. Specifically, we have received another set of device-quality samples, in an attempt to minimize the starting defect densities. We need to minimize these densities to have any chance of improving on our previous results in measuring changes in the NMR on light soaking. We are starting our NMR experiments on these new samples. We are also finishing our NMR studies of samples from United Solar Ovonics, which were purposely made to contain large defect densities. In these samples, using both NMR and FTIR measurements, we have positively identified a hydrogen doublet as due to dihydride bonding sites. In addition, we are continuing our studies of light soaking at 77 K to determine if the Staebler-Wronski effect saturates at this temperature or grows continuously as occurs in the case of the tritium decay in the tritiated samples. We are also preparing a manuscript on the tritiated samples. In this quarter we have made the greatest progress on identifying the hydrogen-hydrogen separation at silicon dihydride bonding sites in a-Si:H.
Venue	U. Utah and Colorado School of Mines, subcontract XXL-5-44205-09, quarterly report
Sources	Colorado School of Mines, Golden, CO; University of Utah
Document Type	Quarterly Report (Word document)
Resource Date	06/26/2006

Post Date	07/25/2006
Title	TRANSPORT, INTERFACES, AND MODELING IN AMORPHOUS SILICON BASED SOLAR CELLS
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Author	E. A. Schiff
Description	CIGS solar cells have two distinct regions. The top region, extending about 0.5 micron below the CdS/TCO interface, drops essentially all of the electric potential across the sample, and leads to capacitances which are larger than the geometrical capacitance of a typical, 2 micron thick cell. The back region, extending 1.5 ? 2 microns beneath the top region, has very little electric potential drop. For time-of-flight measurements, one usually tries to obtain sensitivity to the two photocarriers by using strongly absorbed top illumination for one carrier, and strongly absorbed back illumination for the second carrier. The same electric field polarity, corresponding to reverse biasing of the diode, is used for both experiments. This approach presumes that it is possible to create an essentially uniform electric field across the sample; pulsed voltage bias is usually used in time-of-flight experiments to help achieve this. This approach can't work in CIGS due to the very fast dielectric relaxation time of the back region of the cells. As an alternative, we tried switching from strongly absorbed top illumination (? = 700 nm) to more weakly absorbed top illumination (940 nm). This change actually required that we change nitrogen lasers (to a more powerful one) and purchase special infrared dyes. We do not have independent measurements of the absorption coefficient for our particular samples; some careful work by Alonso, et al. on CIGS with x = 0.2 indicates 50% absorption at depths of 0.1 µm (? = 700 nm) and about 0.3 µm (? = 940 nm). Our paper summarizing our device measurements and modeling for a-Si:H solar nip solar cells from United Solar, as a function of thickness and temperature, were published in January in Applied Physics Letters: J. Liang, E. A. Schiff, S. Guha, B. Yan, and J. Yang, Appl. Phys. Lett. 88 063512 (2006). DOI:10.1063/1.2170405 [.pdf]. While we are satisfied with the conclusion of this paper that the efficiency of as-deposited a-Si:H solar cells is dominated by hole mobility effects (i.e. not defects), the paper establishes what we view as a toolbox for exploring metastability using the modeling approach outlined in this paper.
Venue	Syracuse University, Subcontract NDJ-2-30630-24, quarterly report
Source	Syracuse University
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	06/06/2006

Post Date	07/25/2006
Title	TRANSPORT, INTERFACES, AND MODELING IN AMORPHOUS SILICON BASED SOLAR CELLS
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Author	E. A. Schiff
Description	We continued our work on drift-mobility measurements in CIGS. As noted in previous reports, our hole drift-mobilities in CIGS are about 0.1 cm2/Vs, which is about 30-100 times lower than estimated using admittance measurements by Dave Cohen's group at Oregon. The distinction is very important for understanding solar cells; low-mobility solar cells are understood very differently than are high-mobility cells, and 1 cm2/Vs is about the dividing line between the two types of behavior. In this quarter we have begun to address this apparent discrepancy between the two groups' measurements. If we assume that both our measurements and those of Cohen's group are sound, then there are two physical differences that need to be considered as mechanisms for the difference. The first is a true difference between the samples; Cohen's group has worked primarily with samples from the Institute for Energy Conversion (IEC) at University of Delaware, and we have worked with samples from Noufi's group at NREL. The second is vertical inhomogeneity. We have been exploring the reasons for the fact that the saturation of the Staebler-Wronski effect generally occurs when the degradation of the optoelectronic properties has just become significant ? under solar illumination. The small decline of the open-circuit voltage in working a-Si:H solar cells under illumination is the best indicator of what we term "self-limiting" behavior. Presuming that defect creation is responsible for this degradation, self-limitation implies that the saturation defect density Nsat is comparable to the "crossover density" Ncrossover, where the latter is the defect density for which half of photocarrier recombination occurs at defect sites, and half at bandtail sites. We find that the equation Nsat ? Ncrossover provides a good account for intensity-dependence of Nsat (as reported by other groups). However, this relation predicts that Nsat should be smaller at elevated temperatures than has been reported; T-dependence of Nsat is fairly small.
Venue	Syracuse University, Subcontract NDJ-2-30630-24, quarterly report
Source	Syracuse University
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	06/06/2006

Post Date	05/30/2006
Title	INNOVATIVE CHARACTERIZATION OF AMORPHOUS AND THIN-FILM SILICON FOR IMPROVED MODULE PERFORMANCE
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Author	J. D. Cohen
Description	Although nc-Si:H does not suffer as severely from light exposure as amorphous silicon, prolonged light soaking typically reduces the conversion efficiency by several percent . Several of our samples were examined both in ?State A?, after a sample had been annealed for 1 hour at 450 K, as well as in ?State B?, a degraded state which we obtained by exposing the sample to 20 hours of red-filtered light (>620 nm) from a tungsten-halogen source at an intensity of 400 mW/cm 2. Effects of such light soaking could be observed both in the photo-transient spectra as well as in drive-level capacitance profiles (DLCP). We see that the TPC signal changes significantly. In particular, the negative signals near 1.5 eV become significantly positive in State B. This corresponds to a loss of hole collection, even more than was achieved by reducing the measurement temperature from 295 K to 275 K in State A. What is particularly surprising, however, is that when such a deep defect response is apparent, we consistently have found that it decreased after prolonged light exposure.
Venue	University of Oregon, 3rd Quarterly report, Subcontract ZXL-5-44205-11
Source	University of Oregon
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	05/30/2006

Post Date	07/20/2006
Title	HIGH-EFFICIENCY AMORPHOUS SILICON AND NANOCRYSTALLINE SILICON BASED SOLAR CELLS AND MODULES
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Authors	S. Guha, J. Yang
Description	1. We have achieved active-area (0.25 cm2) initial and stable efficiencies of 9.0% and 8.5%, respectively, for nc-Si:H single-junction cells made with MVHF at a high rate ~ 5-8 Å/s. 2. We have achieved active-area (0.25 cm2) initial and stable efficiencies of 15.1% and 13.3%, respectively, for an a-Si:H/a-SiGe:H/nc-Si:H triple junction cell, where the top and middle cells were made using RF at a low rate ~ 1 Å/s, and the nc-Si:H bottom cell using MVHF at a high rate ~ 5-8 Å/s. 3. We have achieved active-area (0.25 cm2) initial and stable efficiencies of 14.1% and 13.3%, respectively, for an a-Si:H/nc-Si:H/nc-Si:H triple-junction cell, where the top cell was made using RF at a low rate ~ 1 Å/s, and the nc-Si:H middle and bottom cells using MVHF at a high rate ~ 5-8 Å/s. 4. We have demonstrated that an optimized hydrogen dilution profiling not only improves the initial nc-Si:H cell performance but also improves the stability against light soaking. 5. We have shown that the light-induced degradation can be reduced to as low as 3-5% for a-Si:H/nc-Si:H/nc-Si:H triple-junction solar cells by improving the nc-Si:H cell stability.
Venue	Uni-Solar, Subcontract ZXL-6-44205-14, quarterly report
Source	Uni-Solar Ovonic
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	05/26/2006

Post Date	06/01/2006
Title	TRANSPORT, INTERFACES, AND MODELING IN AMORPHOUS SILICON BASED SOLAR CELLS
Link	(MS Word 33 KB)
Author	E. A. Schiff
Description	Our measurements of the hole drift mobilities for two different CIGS depositions by Noufi's group at NREL, and involving many individual sets of contacts on a particular substrate for each deposition, give typical drift mobilities that are small (0.1 ? 0.5 cm2/Vs) and essentially temperature-independent. The temperature-independence is somewhat surprising to us; low drift-mobilities are often caused by traps which bind a photocarrier. Release from such a trap requires thermal excitation, and thus this mechanism gives a strong temperature-dependence to a drift-mobility. The conclusion of weak-temperature dependence for the hole drift-mobility was also reached in capacitance-based measurements by D. Cohen's group. Our manuscript to Applied Physics Letters describing our temperature-dependent solar cell measurements and modeling was accepted. The success of a fairly simple model, involving only bandtail states for as-deposited a-Si:H, has led us to conclude that light-soaking is essentially a "perturbation" of the properties under illumination of the as-deposited state. The hallmark of this statement is the fact that open-circuit voltages decline only quite modestly (perhaps 5%) between the as-deposited and light-soaked states for contemporary a-Si:H solar cells at the light-soaking temperature.
Venue	Subcontract NDJ-2-30630-24, Syracuse University, quarterly report
Source	Syracuse University
Document Type	Quarterly Report (Word document)
Resource Date	03/29/2006

Post Date	05/02/2006
Title	INNOVATIVE CHARACTERIZATION OF AMORPHOUS AND THIN FILM SILICON FOR IMPROVED MODULE PERFORMANCE
Link	(PDF 378 KB) Download Acrobat Reader.
Author	J. D. Cohen
Description	This report documents what we have learned from a set of high performance NREL CIGS devices that were obtained in July, 2005, from Miguel Contreras, comparing the results of our measurements on NREL devices with varying levels of performance. We obtained three samples, each containing 6 devices, with average efficiencies in the 14-15% range (C1919-11), in the 16-17% range (C1818-21), and in the 17-18% range (C1924-1). Among the total of 18 devices, 4 or 5 seemed anomalous (primarily because of low shunt resistances) and we selected 8 of the remaining devices for detailed study that seemed to represent a good range of performance parameters. Drive-level capacitance profiles (DLCP) and CV profiles for representative devices were taken over a broad range of temperatures. The results of these measurements are discussed.
Venue
Source	University of Oregon
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	03/13/2006

Post Date	02/10/2006
Title	SI-BASED SOLAR CELLS
Link	(PDF 1.3 MB) Download Acrobat Reader.
Author	R. W. Birkmire
Description	Aluminum Induced Crystallization
Venue	ADJ-1-30630-12
Source	University of Delaware
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	02/07/2006

Post Date	01/18/2006
Title	INNOVATIVE CHARACTERIZATION OF AMORPHOUS AND THIN-FILM SILICON FOR IMPROVED MODULE PERFORMANCE
Link	(MS Word 202 KB)
Author	J. D. Cohen
Description	We worked on two projects, primarily related to the issues of Narrow Gap Materials and, to a lesser extending, metastable degradation. This work continues our ongoing studies of the HW a-Si,Ge:H alloys produced at NREL, and the properties of nanocrystalline samples (nc Si:H) obtained from United Solar Ovonics Corporation. In spite of the strong evidence that the properties of HWCVD alloy materials ("hot-wire" a-SiGe:H) were so good, initial attempts by NREL with the help of United Solar to demonstrate good cell performance with these materials were unsuccessful. A possible explanation was suggested by some SIMS analysis at NREL showing that the more recently deposited a Si,Ge:H material (including that incorporated in the cell fabrication studies) had a nearly 10-fold increased level of oxygen contamination. We carried out a comparison to to characterize the electronic effects of oxygen inclusion. We also worked on the nc Si:H narrow gap materials that are being developed at United Solar. It now appears that, by incorporating p-i-n nc Si:H as the bottom cell in triple junction, record efficiencies in thin-film Si based PV will soon be achieved. United Solar (B. Yan) sent us a series of 6 nc Si:H devices early in our new Subcontract period. Three of these were deposited by MVHF at a rate of 6Å/s, and the other 3 were deposited by RF at a somewhat lower rate. The MVHF samples were all n i p devices deposited onto SS coated with a textured Ag/ZnO back reflector and were finished with 0.05cm2 ITO top contacts. Two of these devices exhibited relatively high levels of degradation (about 15%) while the third exhibited very little degradation. The three RF nc Si:H samples were fabricated in three different device structures: One was a n-i-p device with a Ag/ZnO textured back reflector, one was a n-i-p device on bare stainless steel, and one was a sandwich device: SS/a Si:H/nc Si:H/a Si:H where the a Si:H capping layers are 0.21mm thick. For all 6 devices the nc Si:H layer was just under 1mm thick. The characteristics of these samples are summarized in Table I. The goal for this series of samples was to find out whether we could distinguish different electronic properties for the high degradation and low degradation films, and whether we could obtain consistent results on the RF samples independent of their different device structures.
Venue
Source	University of Oregon
Document Type	Quarterly Report (Word document)
Resource Date	01/16/2006

Post Date	12/05/2005
Title	SI-BASED SOLAR CELLS
Link	(PDF 5.6 MB) Download Acrobat Reader.
Author	R. W. Birkmire
Description	In the monthly report for March 2005, a design of experiment (DOE) approach was described to continue the study of aluminum induced crystallization (AIC) of Al-Si bilayers. A matrix of samples was created to investigate key variables that had been identified by previous AIC studies at IEC. We are looking for the effect of different structures (normal and reverse), different annealing temperature (above and below eutectic), and annealing time on AIC. The experiments were designed to evaluate the effects of 3 factors on AIC as shown in Table I. The performance of a well-designed co-evaporative physical vapor deposition process for CIGS thin-film growth depends mainly on the ease of controlling individual elemental vapor fluxes. This is done essentially by manipulating the individual source-boat temperature set-points provided by a model predictive controller to achieve the desired film thickness and composition. In such a cascaded control structure, fast and accurate inner-loop controllers are essential. The popular PID controllers are usually employed to control the inner temperature loops.
Venue	ADJ-1-30630-12
Source	University of Delaware
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	11/2005

Post Date	10/28/2005
Title	INNOVATIVE CHARACTERIZATION OF AMORPHOUS AND THIN-FILM SILICON FOR IMPROVED MODULE PERFORMANCE
Link	(MS Word 104 KB)
Author	P. C. Taylor
Description	We have continued collaborations with United Solar Ovonics Corporation on defects that contribute to the Staebler-Wronski effect in modules made using a-Si:H and a-SixGe1-x:H intrinsic layers. We are continuing our collaborations with NREL on defects generated in tritiated a-Si:H and have submitted a paper for publication. In this quarter we have made the greatest progress with our 1H NMR studies (in collaboration with United Solar Ovonics) of hydrogenated amorphous silicon (a-Si:H) with ~10^16 cm-3 defects grown by PECVD at a rate of 5 Å/s. This sample shows the existence of a hydrogen doublet in the as-grown film. We observe the doublet over the temperature range from 5 to 20 K in a sample where no intended light soaking has occurred. The doublet line shapes display no narrowing over this temperature range. Vibrational modes characteristic of SiH2 wagging and scissor modes are seen from infrared spectroscopy. These results suggest that the doublet is due to SiH2 that occurs at a density of approximately 1 at. % in this sample. We estimate a lower limit of 1.8 Å for the hydrogen-to-hydrogen separation for this SiH2 site .
Venue	subcontract XXL-5-44205-09, University of Utah, quarterly report
Source	University of Utah
Document Type	Quarterly Report (Word document)
Resource Date	09/16/2005

Post Date	09/06/2005
Title	HIGH EFFICIENCY NARROW GAP AND TANDEM JUNCTION DEVICES
Link	(PDF 38 KB) Download Acrobat Reader.
Author	V. L. Dalal
Description	In this report, we describe a simple technique that has been used to measure conductivity mobility in the vertical direction on nanocrystalline Si films deposited in device type structures. The technique consists of using space charge limited current (SCLC) in ss/n+nn+/Al type structures deposited on steel substrates. It will be recognized that the first two layers, n+ and n nanocrystalline Si:H on stainless steel , are identical to device type layer which are ss/n+np+. Thus, the measurements represent vertical mobility likely to be operational in solar cell devices.
Venue	ISU subcontract XDJ-2-30630-32, quarterly report
Source	Iowa State University
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	07/16/2005

Post Date	09/06/2005
Title	DEVELOPMENT OF OPTICALLY ENHANCED BACK REFLECTORS AND IMPROVED DEPOSITION PROCESSES FOR AMORPHOUS SILICON-BASED PHOTOVOLTAIC TECHNOLOGIES
Link	(MS Word 4.8 MB)
Author	S. Jones
Description	We have experimented with the use of different ZnAl targets with various Al contents to prepare the Al(specular)/ZnO(textured) back reflectors. The cost of ZnAl targets is significantly less than the ceramic ZnO targets and large area ZnAl targets for use in production machine can easily be obtained from a variety of vendors. Data for bottom a-SiGe cells made using different sputtering targets are shown in Table II. Focusing on the data for Al(specular)/ZnO(textured) back reflectors using metal ZnAl targets, the conductivites of the ZnO layers of the back reflectors made with pure Zn targets were low and thus resulted in low FF and high series resistances. We suspect that the Al doping of the layer is required to achieve low series resistances. When low amounts of Al are used in the targets, the series resistance drops and the FF increases. For cells for back reflectors made using low amounts of Al, the cell efficiencies (Pmax) are similar to those for cells made using the ceramic ZnO. Using high and very high Al contents in the targets, the efficiencies are significantly lower. We believe this is due to the formation of AlOx complexes that limit crystal growth leading to smaller grain sizes. Larger grain and crystal sizes are needed to achieve the light scattering at the ZnO top surface and/or at the grain boundaries.
Venue	ECD, subcontract ZDJ-2-30630-22, quarterly report
Source	Energy Conversion Devices
Document Type	Quarterly Report (Word document)
Resource Date	06/16/2005

Post Date	05/09/2005
Title	INNOVATIVE CHARACTERIZATION OF AMORPHOUS AND THIN-FILM SILICON FOR IMPROVED MODULE PERFORMANCE
Link	(MS Word 2.5 MB)
Author	P. C. Taylor
Description	We have initiated collaborations with United Solar Ovonics Corporation on defects that contribute to the Staebler-Wronski effect in modules made using a-Si:H and a-SixGe1-x:H intrinsic layers. We are continuing our collaborations with NREL on defects generated in tritiated a-Si:H. In this quarter we have made the greatest progress on some important details of the paired hydrogen site that our nuclear magnetic resonance (NMR) measurements have tentatively identified as the defect that stabilizes the silicon dangling bonds that are generated after light exposure (Staebler-Wronski effect). We are currently preparing this work for publication.
Venue	subcontract XXL-5-44205-09, quarterly report
Source	University of Utah
Document Type	Quarterly Report (Word document)
Resource Date	04/30/2005

Post Date	04/22/2005
Title	MEASUREMENT OF DEPOSITING AND BOMBARDING SPECIES INVOLVED IN THE PLASMA PRODUCTION OF AMORPHOUS SILICON AND SILICON/GERMANIUM SOLAR CELLS
Link	(MS Word 679 KB)
Author	A. Gallagher
Description	we report mass-spectrometer measurements of the stable gases produced in the discharge, versus operating conditions. As silane is depleted in the discharge, the silicon atoms go into the a-Si:H film or higher silanes, primarily disilane (Si2H6). The disilane is a minor fraction of the gas, but it plays a major role in the plasma chemistry, and an even larger role is silicon particle growth. We also have to know this to understand our mass spectrometer measurements of Si2Hn radicals that contribute to film growth. Thus, it is desirable to know how much of the depleted silane yields disilane and higher silanes, versus film. This branching has been measured for pure silane discharges, also in this laboratory, but most device deposition is now done using hydrogen-diluted silane. The measurements reported here are for this diluted situation, using conditions that are typical for a-Si:H and ?c-Si film deposition. Our results are available in the publication ?Production of higher silanes in radio frequency SiH4 and H2-SiH4 plasmas?, which is published in J. Appl. Phys. 96, 7660 (2004) and can be obtained from the AIP Online Journals web site.
Venue	DOE Interagency Agreement DE-AC36-02G010244, NIST (Boulder), quarterly report
Source	NIST
Document Type	Quarterly Report (Word document)
Resource Date	04/20/2005

Post Date	04/22/2005
Title	MEASUREMENT OF DEPOSITING AND BOMBARDING SPECIES INVOLVED IN THE PLASMA PRODUCTION OF AMORPHOUS SILICON AND SILICON/GERMANIUM SOLAR CELLS
Link	(MS Word 381 KB)
Author	A. Gallagher
Description	We discuss the design and behavior of the collection and focusing of ions, produced by an e-beam, and their transmission through the mass spectrometer (MS). An overview of the experimental arrangement is provided. Electrostatic lenses focus ions into the mass spectrometer, we also show calculated ion orbits. Due to necessity of detecting low radical densities at the substrate, and the small fraction of radicals exiting the substrate orifice that are ionized by the electron beam, it is important to have efficient ion collection into the MS. The radicals expand thermally from the substrate orifice, and when ionized the ions initially have almost the same (vector) velocity, as if they had started at the orifice. The ion optics is therefore designed to focus the substrate orifice into the MS input orifice.
Venue	DOE Interagency Agreement DE-AC36-02G010244, NIST (Boulder), quarterly report
Source	NIST
Document Type	Quarterly Report (Word document)
Resource Date	04/20/2005

Post Date	04/22/2005
Title	MEASUREMENT OF DEPOSITING AND BOMBARDING SPECIES INVOLVED IN THE PLASMA PRODUCTION OF AMORPHOUS SILICON AND SILICON/GERMANIUM SOLAR CELLS
Link	(MS Word 1.0 MB)
Author	A. Gallagher
Description	We utilize mass spectrometry to measure radical and ion species that arrive at the substrate of a plasma-enhanced-chemical-vapor-deposition (PECVD) reactor. Threshold ionization mass spectrometry (TIMS) is utilized for the radical detection. A small-scale reactor mimics those used to produce hydrogenated amorphous (a-Si:H) and microcrystalline (mc-Si) silicon and silicon/germanium (a-Si:Ge:H) solar cells. Radio frequency (RF) and high frequency (HF) discharges will be studied, and the reactor utilizes a similar electrode gap (2-3 cm), substrate temperature (20-250 °C), gas pressures (0.1-5 Torr), gas mixtures and discharge power density to that used in an industrial reactor. We calibrated the mass spectrometer signals from the discharge for these higher-silane species. We have obtained good signals from the H atom, silane radicals (SiHn, n = 0-3) and disilane radicals (Si2Hn, n = 0-5). Here we will describe the measurements of radicals H, SiHn with n = 0-3 and Si2H2, the most abundant disilane radical. Our primary interest is in measuring these radicals from a RF discharge in a H2/SiH4 mixture, as this is most frequently used for device production. However, to improve understanding of the deposition chemistry, it is of interest to compare the radicals from various H2/SiH4 mixtures to those from a pure silane (inlet flow) vapor.
Venue	Inter-agency agreement DE-AC36-02GO010244 with NIST, quarterly report
Source	NIST
Document Type	Quarterly Report (Word document)
Resource Date	04/20/2005

Post Date	05/24/2005
Title	HIGH-EFFICIENCY NARROW GAP AND TANDEM JUNCTION DEVICES
Link	(PDF 223 KB) Download Acrobat Reader.
Author	V. L. Dalal
Description	During this period, we concentrated on improving the stability of a-Si devices by using chemical annealing techniques. Chemical annealing technique was claimed by the Shimizu group to produce materials with significantly improved stability. We decided to try to replicate these results by using chemical annealing with He. The films and i layers in devices were deposited using a layer-by-layer deposition method, using the low pressure ECR reactor described earlier. The growth cycle was generally 8 or 10 seconds, during which the flow of silane was set to on. During the growth cycle, the gases used were silane, hydrogen and helium. Then, for different anneal periods, only helium was present in the reactor. The plasma was continuously on during the growth and anneal cycles. The growth cycle was such as to grow about 2-3 nm thick films. The anneal cycle times were systematically varied between 10 and 60 seconds. There were no significant changes to either device or film properties when the anneal cycle time was 10 seconds. However, when the anneal cycle time was increased to 20 seconds and beyond, the films became nanocrystalline. This was a surprising result, since during annealing, only helium was flowing. The crystalline signature of both films and devices was verified using both Raman spectroscopy and x-ray diffraction. The devices showed all the characteristics of nanocrystalline base layers, including QE extending out towards the infrared region, and the voltage in the device reducing to the 0.5 V range from the typical 0.8+ V for a-Si:H.
Venue	subcontract XDJ-2-30630-32, quarterly report
Source	Iowa State University
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	04/16/2005

Post Date	05/26/2005
Title	DEVELOPMENT OF OPTICALLY ENHANCED BACK REFLECTORS AND IMPROVED DEPOSITION PROCESSES FOR AMORPHOUS SILICON-BASED PHOTOVOLTAIC TECHNOLOGIES
Link	(MS Word 575 KB)
Author	S. Jones
Description	In this program, we plan to improve the module efficiencies through development of a new optically enhanced Al/ZnO back reflector and improved i-layer deposition process. In the case of the back reflector development, a multi-layered thin film structure consisting of films with contrasting indices of refraction placed between the Al and ZnO layers of the back reflector will be developed. These new types of back reflectors will be tested in amorphous silicon based single junction and multi-junction devices. The differences in n of the different layers of the multi-layered back reflector and electrical conduction through the multi-layered structure will be optimized to obtain the highest reflection values, highest currents and best cell performance. The ultimate goal is to achieve the high currents and cell efficiencies typically obtained with the Ag/ZnO back reflector with a new optically enhanced back reflector that can be used in the solar module products. For the multi-layered structure, focus will be on preparing the layers using sputtering techniques so that this technology might be quickly applied to ECD?s present back reflector fabrication process that uses sputtering techniques. In the case of the i-layer, the focus will be on preparing microcrystalline silicon based intrinsic layers for low cost, high stable efficiency solar cells through the use of microwave plasmas. In these studies, the effects of such deposition conditions as ion bombardment, substrate temperature and etchant gases on the grain size and film transparency will be studied and correlated with cell performance.
Venue	subcontract ZDJ-2-30630-22, quarterly report
Source	Energy Conversion Devices
Document Type	Quarterly Report (Word document)
Resource Date	03/16/2005

Post Date	05/13/2005
Title	CENTER OF EXCELLENCE
Link	(PDF 174 KB) Download Acrobat Reader.
Authors	R. W. Birkmire, S. S. Hegedus
Description	This report covers research conducted at the Institute of Energy Conversion (IEC) for the period Feb. 09, 2005 to Mar. 09, 2005, under the subject subcontract. The report highlights progress and results obtained under Task 3 (Si-based Solar Cells).
Venue	ADJ-1-30630-12
Source	University of Delaware
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	03/2005

Post Date	04/15/2005
Title	HIGH-EFFICIENCY AMORPHOUS SILICON ALLOY BASED SOLAR CELLS AND MODULES
Link	(PDF 762 KB) Download Acrobat Reader.
Authors	S. Guha, J. Yang
Description	We have improved the deposition process for the Ag and ZnO layers by changing the deposition process to modify the surface morphology to achieve a high light trapping effect. We used chemical etching to modify the BR subsurface and studied the correlation of the fabrication process of BR, surface morphology measured by AFM, and solar cell performance. The experimental results show that the BRs with large micro-features increase the short-circuit current density (Jsc) of nc-Si:H by enhancing long wavelength response and improve the open-circuit voltage (Voc) of a-SiGe:H bottom cells by reducing back diffusion and shunt current density. We have explored a new deposition regime under high pressure to enhance the deposition rate for nc-Si:H. Currently, we are working at ~6-10 Å/s corresponding to an intrinsic layer deposition time of 20-30 minutes. We have achieved an initial active-area efficiency of 8.2% for a nc-Si:H single-junction solar cell, where the intrinsic layer was deposited for 30 minutes. We have achieved an initial active-area (0.25 cm2) efficiency of 12% using an a-Si:H/nc-Si:H double-junction structure. Currently, we are using the new recipe to make large-area modules. In addition, we have light-soaked the mini-modules (aperture area of 45 cm2) made in the last quarter. Those modules showed an initial aperture-area efficiency of 11.3% and stabilized to 10.2%.
Venue	Subcontract ZDJ-2-30630-19 quarterly report
Source	Uni-Solar Ovonic
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	02/28/2005

Post Date	04/22/2005
Title	MEASUREMENT OF DEPOSITING AND BOMBARDING SPECIES INVOLVED IN THE PLASMA PRODUCTION OF AMORPHOUS SILICON AND SILICON/GERMANIUM SOLAR CELLS
Link	(MS Word 172 KB)
Author	A. Gallagher
Description	We describe film-growth measurements in our film-deposition reactor. Most industrial and experimental reactors measure the ratio (R) of H2 versus SiH4 flows, the reactor chamber pressure (PCh) and the power (Ptot) delivered to a matching network that is connected to the discharge RF electrode. Since only 10-20% of Ptot is typically dissipated in the discharge, and this fraction is generally not known or controlled, it is difficult to relate the conditions of different reactors. The film growth rate (G) is also measured by device manufacturers and developers, and as G is a monotonic function of power delivered to the discharge we use it to characterize the power conditions. The RF voltage (VRF) applied to the discharge is easy to measure, and is also monotonically related to the discharge power, so we measure G versus R, PCh and VRF to relate our conditions to those of device makers. In essence, similar conditions exist in different reactors when the values of G, R and PCh are the same.
Venue	Iteragency Agreement DE-AC36-02GO010244 with NIST (Boulder), quarterly report
Source	NIST
Document Type	Quarterly Report (Word document)
Resource Date	02/20/2005

Post Date	05/09/2005
Title	TRANSPORT, INTERFACES, AND MODELING IN AMORPHOUS SILICON BASED SOLAR CELLS
Link	(MS Word 33 KB)
Author	E. A. Schiff
Description	The main work during this quarter has been on a-Si:H solar cell characterization & modeling, and in particular on the time-dependence of the degradation of the open-circuit voltage. We have been fairly successful in accounting for the measurements of the time-dependence of degradation with an elementary model. Additional, rather interesting results emerged from measurements of hole drift-mobilities in CIGS. The hole drift-mobility appears rather low (less than 0.1 cm2/Vs), and nearly temperature-independent. If these results are confirmed, they would indicate that CIGS solar cells are actually low-mobility cells and possibly mobility-limited. Finally, we have found a good tool for exploring VOC in a-Si:H and c-Si solar cells with polymer p-layers, and are exploring VOC as a function of the resistivity of the polymer layer.
Venue	subcontract NDJ-2-30630-24, quarterly report
Source	Syracuse University
Document Type	Quarterly Report (Word document)
Resource Date	02/10/2005

Post Date	05/26/2005
Title	OPTIMIZATION OF PHASE-ENGINEERED A-SI:H- BASED MULTIJUNCTION SOLAR CELLS
Link	(PDF 684 KB) Download Acrobat Reader.
Authors	R. W. Collins, C. Wronski
Description	1. Materials Research and Device Development: RTSE has been applied to analyze growth processes for a-Si1-xGex:H thin films, providing insights into optimization of this material as the bottom cell i-layer in triple-junction devices. Two types of excursions in parameter space were explored starting from the optimized set of conditions adopted previously for a-Si:H, i.e., 200°C, lowest power, and low reactive gas partial pressure. These excursions were designed to obtain the smoothest surfaces and largest ranges of surface stability in the a-Si1-xGex:H deposition process. Modest improvements in surface stability were achieved with increasing temperature to ~300°C; however, major improvements were made at 200°C by altering the deposition electrode from anode to cathode. 2. Device Loss Mechanisms: It is shown that from the JD-V characteristics it is possible to identify and quantify the limitation imposed on 1 sun Voc by bulk recombination. As a consequence, it is possible to relate the light induced changes in JD-V characteristics to those in 1 sun Voc for cells with undiluted and diluted protocrystalline i-layers. In addition, the new approach in the analysis of JD-V characteristics in terms of differential diode quality factor n(V) has allowed these differences to be directly related to those in the distributions of gap states in the corresponding i-layers. The results further illustrate the serious limitations of attempts to correlate solar cell characteristics with neutral dangling bond densities, subgap absorption characterized at arbitrarily chosen photon energies or just valence band tails. 3. Characterization Strategies for Advanced Materials: The kinetics of the changes in the light induced defect states at room temperature after 1 sun illumination have been characterized with photocurrents on films and bulk recombination currents on corresponding solar cells. The self-consistency of the two types of results further confirms that the relaxations observed in films are indeed a bulk effect.
Venue
Source	Pennsylvania State University
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	02/01/2005

Post Date	02/18/2005
Title	HIGH-EFFICIENCY AMORPHOUS SILICON ALLOY BASED SOLAR CELLS AND MODULES
Link	(PDF 1.6 MB) Download Acrobat Reader.
Authors	S. Guha, J. Yang
Description	1. We have worked on the optimization of Ag/ZnO back reflector for a-SiGe:H and nc-Si:H solar cells. We have improved the deposition process for the Ag and ZnO layers to modify the surface morphology to achieve a high light trapping effect. The newly developed Ag/ZnO back reflector improves not only the short-circuit current density (Jsc) by enhancing long wavelength response, but also the fill factor (FF) and the open-circuit voltage (Voc) of a-SiGe:H bottom cells. The improvement in the cell performance correlates to the scattering of light due to improved texture surface. 2. In the area of high rate deposition, we have continued our work on nc-Si:H using MVHF glow discharge. We have explored a new deposition regime under high pressure to enhance the deposition rate. Currently, we are working at ~6-10 Å/s corresponding to an intrinsic layer deposition time of 20-25 minutes. We light-soaking our previous "champion" high rate triple-junction cells. A stabilized active-area efficiency of 11.3% has been obtained. 3. We have continued to optimize the a-SiGe:H middle and bottom cells under the constraints of the production machine. We have also worked on the nc-Si:H solar cells at high deposition rates. Currently, the deposition rate is around 3-5 Å/s, corresponding to an intrinsic layer deposition time of 50-60 minutes. We have achieved an initial aperture-area efficiency of 11.4% using an a-Si:H/nc-Si:H double-junction structure with an aperture area of 45 cm2. 4. We have continued to study the metastability of nc-Si:H solar cells. We focused on the reverse-bias enhanced light-induced degradation in nc-Si:H solar cells using various experimental methods and proposed a model based on the heterogeneity of the material structure.
Venue	subcontract ZDJ-2-30630-19, United Solar Ovonic Corp.
Source	Uni-Solar Ovonic
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	01/26/2005

Post Date	02/18/2005
Title	HIGH EFFICIENCY NARROW GAP AND TANDEM JUNCTION DEVICES
Link	(MS Word 353 KB)
Author	V. L. Dalal
Description	We discovered that nc-Si can be made without any deliberately added hydrogen by doing a chemical anneal of thin layers of a-Si using a layer-by-layer growth technique. We grew thin layers (~2.5 nm) of a-Si:H using standard ECR process with He and hydrogen dilution, and then annealed the films in He alone for varying times and then repeated the cycle until we obtained films approximately 0.5-1.0 micrometer thick. For short annealing times (10 sec), the films and devices remained amorphous. However, when the annealing time was increased to 20 seconds, the films and the devices became nanocrystalline. Note that there was no deliberately introduced hydrogen during the annealing cycle. Films were characterized and solar cells fabricated.
Venue	subcontract XDJ-2-30630-32, Iowa State University
Source	Iowa State University
Document Type	Quarterly Report (Word document)
Resource Date	01/16/2005

Post Date	05/23/2005
Title	DEVELOPMENT OF OPTICALLY ENHANCED BACK REFLECTORS AND IMPROVED DEPOSITION PROCESSES FOR AMORPHOUS SILICON-BASED PHOTOVOLTAIC TECHNOLOGIES
Link	(MS Word 2.5 MB)
Author	S. Jones
Description	We are currently working on Al/Multi-layer (ML)/ZnO structure where ML is ZnO/ZnOSi/Si/ZnOSi where the ZnOSi is the low index of refraction layer and Si is the high index of refraction layer. In our last report, we showed the increased solar cell performance obtained when the ML structure was added to back reflectors using flat specular back reflector surfaces. This month, we have further optimized the multi-layer structure to increase the performance of the non-textured back reflector with the increases in red light (?>630nm) performance with the improvements in Pmax for single-junction a-SiGe cells.
Venue	subcontract ZDJ-2-30630-22, quarterly report
Source	Energy Conversion Devices
Document Type	Quarterly Report (Word document)
Resource Date	12/16/2004

Post Date	05/09/2005
Title	TRANSPORT, INTERFACES, AND MODELING IN AMORPHOUS SILICON BASED SOLAR CELLS
Link	(MS Word 39 KB)
Author	E. A. Schiff
Description	The main work during this quarter has been on a-Si:H solar cell characterization & modeling. Additional work was done on drift-mobilities in H-diluted a-Si:H and on a review of drift-mobilities, and on the use of polymeric p-layers for a-Si:H solar cells.
Venue	subcontract NDJ-2-30630-24, quarterly report
Source	Syracuse University
Document Type	Quarterly Report (Word document)
Resource Date	11/10/2004

Post Date	02/18/2005
Title	CHARACTERIZATION OF AMORPHOUS SILICON ADVANCED MATERIALS AND PV DEVICES
Link	(MS Word 1.1 MB)
Author	P. C. Taylor
Description	We have made the greatest progress on the growth of tritium-induced defects in tritium doped hydrogenated amorphous silicon (a-Si:H,T) as measured by electron spin resonance (ESR) and photothermal deflection spectroscopy (PDS). These measurements allow us to examine the production of defects in a-Si:H,T where the defect production mechanism is known (tritium decay to He). In addition, we have examined the annealing kinetics of the tritium-decay-induced metastable defects.
Venue	Subcontract No. ADJ-2-30630-23, University of Utah
Source	University of Utah
Document Type	Quarterly Report (Word document)
Resource Date	10/15/2004

Post Date	05/11/2005
Title	NREL SUBCONTRACT ADJ-2-30630-17
Link	(PDF 701 KB) Download Acrobat Reader.
Author	J. D. Cohen
Description	We report the results of our research activities under NREL Subcontract ADJ-2-30630-17 during the third quarter of Phase III. During this quarter we have been working on two projects primarily related to the Narrow Gap Materials reporting umbrella: Examining the properties of nanocrystalline samples (nc-Si:H) obtained from United Solar Ovonics Corporation, and the properties of HW a-Si,Ge:H alloys produced at NREL.
Venue	28 May 2004 to 15 October 2004
Source	University of Oregon
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	10/2004

Post Date	03/07/2005
Title	DEVELOPMENT OF OPTICALLY ENHANCED BACK REFLECTORS AND IMPROVED DEPOSITION PROCESSES FOR AMORPHOUS SILICON-BASED PHOTOVOLTAIC TECHNOLOGIES - JUNE 14, 2004 - SEPTEMBER 15, 2004
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Authors	S. Jones, et al.
Description	In this program, we plan to improve the module efficiencies through development of a new optically enhanced Al/ZnO back reflector and improved i-layer deposition process. In the case of the back reflector development, a multi-layered thin film structure consisting of films with contrasting indices of refraction placed between the Al and ZnO layers of the back reflector will be developed. These new types of back reflectors will be tested in amorphous silicon based single junction and multi-junction devices. The differences in n of the different layers of the multi-layered back reflector and electrical conduction through the multi-layered structure will be optimized to obtain the highest reflection values, highest currents and best cell performance. The ultimate goal is to achieve the high currents and cell efficiencies typically obtained with the Ag/ZnO back reflector with a new optically enhanced back reflector that can be used in the solar module products. For the multi-layered structure, focus will be on preparing the layers using sputtering techniques so that this technology might be quickly applied to ECD?s present back reflector fabrication process that uses sputtering techniques. In
Venue	Subcontract
Source	Energy Conversion Devices
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	09/15/2004

Post Date	05/25/2005
Title	HIGH EFFICIENCY AND HIGH RATE DEPOSITED AMORPHOUS SILICON-BASED SOLAR CELLS
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Author	X. Deng
Description	Ethyl vinyl acetate (EVA) is the most commonly used material for the encapsulation of terrestrial solar cells. It is well known that EVA turns yellow upon extended exposure to ultraviolet light. This yellowing upon exposure to UV light is a characteristic of most carbon based polymers. Silicon-based polymers (silicones) may not show this effect. Although silicones were used to encapsulate solar cells in the 1970s and 1980s, they were dropped in favour of ethyl vinyl acetate due to its lower cost. However, the price of silicone elastomers has come down over the years and their quality and ease of application have improved, which may make them suitable for encapsulating solar cells once again. We have recently fabricated 4?x 4? and 4?x8? minimodules encapsulated with a combination of a silicone elastomer and Dupont Tefzel.
Venue	subcontract NDJ-2-30630-08, quarterly report
Source	University of Toledo
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	09/01/2004

Post Date	03/22/2005
Title	HIGH-EFFICIENCY AMORPHOUS SILICON ALLOY BASED SOLAR CELLS AND MODULES
Link	(PDF 564 KB) Download Acrobat Reader.
Author	S. Guha
Description
Venue	ZDJ-2-30630-19 Quarterly Technical Progress Report June 1, 2004 through August 31, 2004
Source	Uni-Solar Ovonic
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	09/2004

Post Date	03/07/2005
Title	HIGH EFFICIENCY AND HIGH RATE DEPOSITED AMORPHOUS SILICON-BASED SOLAR CELLS
Link	(PDF 119 KB) Download Acrobat Reader.
Author	X. Deng
Description	PHASE III Fourth Quarter Technical Progress Report June 1, 2004 to August 31, 2004.
Venue	Subcontract Report
Source	University of Toledo
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	08/31/2004

Post Date	05/10/2005
Title	OPTIMIZATION OF PHASE-ENGINEERED A-SI:H- BASED MULTIJUNCTION SOLAR CELLS
Link	(PDF 644 KB) Download Acrobat Reader.
Authors	R. W. Collins, C. Wronski
Description	There is considerable motivation for establishing a better understanding of the growth processes for a-Si1-xGex:H alloys. This may be possible through the application of real time spectroscopic ellipsometry (RTSE) to the development of deposition phase diagrams for a-Si1-xGex:H. With this approach, directions for possible improvements to existing world-record performance a-Si:H-based solar cells can be suggested. The ability to create in a controlled way metastable defects in the i-layers with carrier recombination under forward bias and the equivalence between this and the corresponding creation with illumination has been further established. We study the fast and slow state creation obtained with different carrier recombination rates and the kinetics of their subsequent relaxation in order to directly identify separate and quantify the contributions of ?light annealing?. Characterization Strategies for Advanced Materials Studies are continuing on both diluted and undiluted a-Si:H thin films of the evolution of light induced defect states under 1 sun illumination and their subsequent relaxation. An experimental station has been constructed with precise control of the sample temperatures asr rates.
Venue	subcontract NDJ-1-30630-01, quarterly report
Source	Pennsylvania State University
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	08/31/2004

Post Date	04/19/2005
Title	HIGH EFFICIENCY AND HIGH RATE DEPOSITED AMORPHOUS SILICON-BASED SOLAR CELLS
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Author	J. Deng
Description	Two minimodules were fabricated from 4?x4? single junction amorphous silicon-germanium solar cells and encapsulated with Sylgard 182 and Tefzel in the vacuum laminator. The first minimodule had a single 4?x4? a-SiGe n-i-p cell while the second consisted of two 4?x4? cells in series. Each cell had an active area of approximately 81 cm^2. Current collection grids consisting of tinned copper wire applied to the ITO front contact with conductive silver paint for the series interconnected cells, and conducting graphite paint for the single cell. Reverse-protection diodes were also attached between the bus bars of the cells. Before application of grids, the cells were shunt-passivated using a light-assisted electrochemical method.
Venue	subcontract NDJ-2-30630-08, quarterly report
Source	University of Toledo
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	08/31/2004

Post Date	05/10/2005
Title	NREL SUBCONTRACT # ADJ-1-30630-12
Link	(PDF 437 KB) Download Acrobat Reader.
Author	R. W. Birkmire
Description	a-Si and CdTe
Venue
Source	University of Delaware
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	08/23/2004

Post Date	05/10/2005
Title	TRANSPORT, INTERFACES, AND MODELING IN AMORPHOUS SILICON BASED SOLAR CELLS
Link	(MS Word 202 KB)
Author	E. A. Schiff
Description	Two themes of our recent work have been (i) that hole drift-mobilities have more predictive power for describing a-Si solar cell efficiencies than we had previously suspected, and (ii) that we don?t know nearly enough about which deposition variables affect the holes.The main experimental activity in this quarter has been to measure hole drift-mobilities on a series of cells made some time ago with differing hydrogen dilutions at BP Solar. This is our second attempt with these cells, which needed to be modified to reduce the series resistance. We had presumed that hydrogen dilution would have a simple effect on the cells, but we haven?t been able to establish such an effect experimentally. We have been making temperature-dependent J-V measurements on a series of cells from United Solar Ovonics using uniformly absorbed laser illumination; the purpose is to generate a target set of measurements for modeling activities. We have extended our measurements to include light-soaking effects. The measurements are done on a fairly thick nip cell (900 nm) using strong laser illumination (Jsc is about 5 mA/cm2). Light-soaking was done using the same illumination level under open-circuit conditions. For the lowest temperatures (about 230 K), light-soaking has a negligible effect on VOC.
Venue	subcontract NDJ-2-30630-24, quarterly report
Source	Syracuse University
Document Type	Quarterly Report (Word document)
Resource Date	08/10/2004

Post Date	02/18/2005
Title	CHARACTERIZATION OF AMORPHOUS SILICON ADVANCED MATERIALS AND PV DEVICES
Link	(MS Word 68 KB)
Author	P. C. Taylor
Description	We have continued collaborations with Penn State University on comparisons of ESR and optical absorption and with NREL on tritiated a-Si:H. In this quarter we have made the greatest progress on the ESR measurements on light soaked and annealed samples of a-Si:H in collaboration with the group at Penn State University.
Venue	subcontract ADJ-2-30630-23, University of Utah
Source	University of Utah
Document Type	Quarterly Report (Word document)
Resource Date	07/16/2004

Post Date	03/11/2005
Title	QUARTERLY PROGRESS REPORT FOR APRIL 14-JULY 15,2004
Link	(MS Word 158 KB)
Author	V. L. Dalal
Description	Changes in microstructure of nanocrystalline Si:H films and Measurement and influence of stress in the nanocrystalline Si:H films
Venue	Subcontract Report
Source	Iowa State University
Document Type	Quarterly Report (Word document)
Resource Date	07/15/2004

Post Date	04/22/2005
Title	THE MICROSCOPIC MECHANISMS OF THE STAEBLER-WRONSKI EFFECT IN A-SI FILMS AND HIGH-EFFICIENCY SOLAR CELLS
Link	(MS Word 112 KB)
Author	D. Han
Description	Two series of µc-Si:H single-junction solar cells with thickness from 0.3-µm to 2.0-µm were studied using Micro-Raman spectroscopy. The deposition condition of the intrinsic layers was the same for all of the samples except the deposition time of the intrinsic layer. One set of the samples was deposited on the textured Ag/ZnO back reflectors (BR), and the other on specular stainless steel (SS). X-ray diffraction (XRD) results have shown that the crystallinity increases with the µc-Si:H film thickness. We used Micro-Raman spectroscopy to study the effects of thickness on i-layer structures and the electronic density of states of the solar cells.
Venue	Subcontract ADJ-1-30630-09, quarterly report
Source	University of North Carolina, Chapel Hill
Document Type	Quarterly Report (Word document)
Resource Date	07/12/2004

Post Date	02/09/2005
Title	SI AND DIAGNOSTICS
Link	(PDF 239 KB) Download Acrobat Reader.
Author	R. W. Birkmire
Description
Venue	ADJ-1-30630-12
Source	University of Delaware
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	06/03/2004

Post Date	05/25/2005
Title	HIGH EFFICIENCY AND HIGH RATE DEPOSITED AMORPHOUS SILICON-BASED SOLAR CELLS
Link	(PDF 447 KB) Download Acrobat Reader.
Author	X. Deng
Description	Triple junction a-Si solar cells have been modeled and simulated using the Advanced Semiconductor Analysis (ASA). The device performance is analyzed with numerically simulated IV characteristics. We have studied several failure scenarios such as variations in the thickness of different layers of the multilayered triple-junction structure. Distinctive features of the I-V characteristics and solar parameters have been found which have been correlated and discussed with the basis of device physics.
Venue	subcontract NDJ-2-30630-08, quarterly report
Source	University of Toledo
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	06/01/2004

Post Date	03/11/2005
Title	?THIN FILM SI BOTTOM CELLS FOR TANDEM DEVICE STRUCTURES?
Link	(MS Word 232 KB)
Authors	A. Rohatgi, et al.
Description	This report summarizes the progress in the development of deposited emitter and contact layers for heterojunction a-Si/c-Si solar cells. The work reported here was performed to meet the objectives of Task 1 in Phase 1 of the collaborative subcontract titled Thin Film Si Bottom Cells for Tandem Device Structures as part of the High-Performance Photovoltaic Project initiated by the Department of Energy. The objectives of Task 1 addressed in Phase 1 include the fabrication of thin film Si/c-Si and thin film Si/thick polycrystalline Si heterojunction cells with deposited emitter and contact layers (p-i and n-i structures) deposited by PECVD. In this report, HIT-type devices are fabricated and analyzed using c-Si wafers prepared at Georgia Tech (GT) with p-i and n-i a-Si layers deposited at the Institute for Energy Conversion (IEC). In some cases, c-Si and c-Si solar cells are fabricated with deposited emitter layers and screen-printed back contacts.
Venue	Subcontract Report
Source	Georgia Institute of Technology
Document Type	Quarterly Report (Word document)
Resource Date	06/2004

Post Date	04/19/2005
Title	HIGH EFFICIENCY AND HIGH RATE DEPOSITED AMORPHOUS SILICON-BASED SOLAR CELLS
Link	(PDF 447 KB) Download Acrobat Reader.
Author	X. Deng
Description	Triple junction a-Si solar cells have been modeled and simulated using the Advanced Semiconductor Analysis (ASA). The device performance is analyzed with numerically simulated IV characteristics. We have studied several failure scenarios such as variations in the thickness of different layers of the multilayered triple-junction structure. Distinctive features of the I-V characteristics and solar parameters have been found which have been correlated and discussed with the basis of device physics.
Venue	Subcontract NDJ-2-30630-08, quarterly report
Source	University of Toledo
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	05/31/2004

Post Date	02/08/2005
Title	THIN FILM SILICON CELLS ON LOW-COST SUBSTRATES (DE-AC36-99GO10337)
Link	(MS Word 614 KB)
Author	H. A. Atwater
Description	Observation of long minority carrier lifetimes in 1-15 micron thick Si films grown by HWCVD on n⁺ large-grained polysilicon epitaxial templates on glass and also on Si (001). Minority carrier lifetimes ranging from 5-20 microseconds were measured using rf photoconductive decay measurement techniques, suggesting that minority carrier diffusion lengths in excess of the pn cell base thickness can be achieved for HWCVD polysilicon films up to 15 microns thick. These results also suggest that hydrogen passivation of grain boundaries may be very effective in HWCVD poly-Si.
Venue	NREL subcontract
Source	California Institute of Technology
Document Type	Quarterly Report (Word document)
Resource Date	05/31/2004

Post Date	02/08/2005
Title	STRUCTURE OF SILICON-BASED THIN FILM SOLAR CELL MATERIALS
Link	(PDF 451 KB) Download Acrobat Reader.
Author	D. L. Williamson
Description	During this third quarter of Phase II of the NREL subcontract we have addressed issues related to Tasks 1,2 and 3: Task 1 - Electron Microscopy and Spectrometry Experiments, Task 2 - Small-angle Scattering Experiments, and Task 3 - Wide-angle X-ray Diffraction Experiments. Specific experiments and results from each of the tasks are presented below.
Venue	NREL Subcontract
Source	Colorado School of Mines, Golden, CO
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	05/31/2004

Post Date	05/09/2005
Title	TRANSPORT, INTERFACES, AND MODELING IN AMORPHOUS SILICON BASED SOLAR CELLS
Link	(MS Word 40 KB)
Authors	A. R. Middya, E. A. Schiff
Description	We are working on techniques for hole drift-mobility measurements in pin cells prepared on stainless steel substrates. Such measurements have not been reported previously, but could be valuable in understanding substrate-type solar cells. We now have a set of temperature (220 ? 350 K) and intensity-dependent J-V measurements on a series of cells made at United Solar with varying intrinsic layer thickness. The measurements are done using monochromatic illumination. We are working on modeling of these measurements using a model based mainly on hole drift mobilities. We have made some devices with a-Si:H n and i layers and a polyaniline-based p-layer. The open-circuit voltages obtained are about 0.7 V at present.
Venue	subcontract NDJ-2-30630-24, quarterly report
Source	Syracuse University
Document Type	Quarterly Report (Word document)
Resource Date	05/10/2004

Post Date	02/08/2005
Title	QUARTERLY TECHNICAL REPORT 28 MAY 2004 TO 15 OCTOBER 2004 NREL SUBCONTRACT ADJ-2-30630-17
Link	(PDF 691 KB) Download Acrobat Reader.
Author	J. D. Cohen
Description	We report the results of our research activities under NREL Subcontract ADJ-2-30630-17 during the third quarter of Phase III. During this quarter we have been working on two projects primarily related to the Narrow Gap Materials reporting umbrella: Examining the properties of nanocrystalline samples (nc-Si:H) obtained from United Solar Ovonics Corporation, and the properties of HW a-Si,Ge:H alloys produced at NREL.
Venue
Source	University of Oregon
Document Type	Quarterly Report (Adobe Postscript file)
Resource Date	05/2004

Post Date	05/16/2005
Title	SUBCONTRACT ADJ-2-30630-17
Link	(PDF 211 KB) Download Acrobat Reader.
Author	J. D. Cohen
Description	We report the results of our rese