Publications, Presentations, and News Database

Copper Indium Diselenide

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

With 19.5% efficiency under standard test conditions, the best CIS cell is about as efficient as the best polycrystalline-silicon cell. The potential for high module efficiencies and low cost has led to a large increase in private investment. However, the technology still has barriers to address before it will succeed in the marketplace.

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	10/11/2007
Title	STUDY OF THE ELECTRONIC PROPERTIES OF MATCHED NA-CONTAINING AND NA-FREE CIGS SAMPLES USING JUNCTION CAPACITANCE METHODS
Link	(PDF 151 KB) Download Acrobat Reader.
Authors	P. T. Erslev, A. F. Halverson, J. D. Cohen, W. N. Shafarman
Description	Junction capacitance methods were used to examine a matched pair of Cu(InxGa1-x)Se2 (CIGS) thin film solar cells, one with Na incorporated into the absorber and the other with a diffusion barrier to inhibit the Na incorporation from the soda-lime glass. Typical cells showed a 50% increase in efficiency with the addition of Na to the devices. Forward biased admittance spectroscopy revealed a large defect density located near the CdS/CIGS heterojunction in the Na-less samples not present in the Na samples. This defect may be responsible for the loss in Voc which contributes to the loss in efficiency when Na is not added to the devices. Drive Level Capacitance profiles revealed free carrier densities of 3�10^14 cm^-3 and 1.1�10^14 cm-3 for the Na and Na-less samples, respectively. Transient photocapacitance spectra also showed interesting differences between the samples, but nothing significant enough to account for the magnitude of loss in efficiency.
Venue	MRS Spring Meeting, San Francisco 04/2007
Source	University of Oregon
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	04/2007

Post Date	04/30/2007
Title	&NBSP; VOLTAGE DEFICIT IN THIN-FILM POLYCRYSTALLINE SOLAR CELLS
Link	(MS Word 46 KB)
Author	J. R. Sites
Description	The highest reported efficiency for thin-film CIGS solar cells is 3% larger than the highest seen with CdTe cells. The lower CdTe efficiency is the result of a much larger voltage deficit between CdTe cells and crystalline cells of similar band gap. The explanation for the difference is that CIGS has a natural energy barrier, which repels holes from grain boundaries, but CdTe does not. Significant efficiency increases in CdTe cells will therefore likely require new structures with full absorber depletion and electron reflection at the back contact.
Venue	DOE Solar Technology Review Meeting, Denver, CO 4/17-17/2007
Source	Colorado State University
Document Type	Conference Papers (Word document)
Resource Date	03/2007

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	05/18/2006
Title	HIGH-EFFICIENCY CDTE AND CIGS THIN-FILM SOLAR CELLS: HIGHLIGHTS AND CHALLENGES
Link	(MS Word 602 KB)
Authors	R. Noufi, K. Zweibel
Description	Thin-film photovoltaic (PV) modules of CdTe and Cu(In,Ga)Se2 (CIGS) have the potential to reach cost-effective PV-generated electricity. These technologies have transitioned from the laboratory to the market place. Pilot production and first-time manufacturing are ramping up to higher capacity and enjoying a flood of venture-capital funding. CIGS solar cells and modules have achieved 19.5% and 13% efficiencies, respectively. Likewise, CdTe cells and modules have reached 16.5% and 10.2% efficiencies, respectively. Even higher efficiencies from the laboratory and from the manufacturing line are only a matter of time. Manufacturing-line yield continues to improve and is surpassing 85%. Long-term stability has been demonstrated for both technologies; however, some failures in the field have also been observed, emphasizing the critical need for understanding degradation mechanisms and packaging options. These two thin-film technologies have a common device/module structure: substrate, base electrode, absorber, junction layer, top electrode, patterning steps for monolithic integration, and encapsulation. The monolithic integration of thin-film solar cells can lead to significant manufacturing cost reduction compared to crystalline Si technology. The CdTe and CIGS modules share common structural elements. In principle, this commonality should lead to similar manufacturing cost per unit area, and thus, the module efficiency becomes the discriminating factor that determines the cost per watt. The long-term potential of the two technologies require R&D emphasis on science and engineering-based challenges to find solutions to achieve targeted cost-effective module performance, and in-field durability. Some of the challenges are common to both, e.g., in-situ process control and diagnostics, thinner absorber, understanding degradation mechanisms, protection from water vapor, and innovation in high-speed processing and module design. Other topics are specific to the technology, such as lower-cost and fast-deposition processes for CIGS, and improved back contact and voltage for CdTe devices.
Venue	WPEC4, Hawaii
Source	National Renewable Energy Laboratory
Document Type	Conference Papers (Word document)
Resource Date	05/2006

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	08/25/2006
Title	POLYCRYSTALLINE THIN-FILM PHOTOVOLTAICS: FROM THE LABORATORY TO SOLAR FIELDS
Link	(PDF 682 KB) Download Acrobat Reader.
Authors	B. Von Roedern, H. S. Ullal, K. Zweibel
Description	We review the status of commercial polycrystalline thin-film solar cells and photovoltaic (PV) modules, including current and projected commercialization activities. Major technical progress has occurred in the area of thin-film PV technologies, particularly those based on cadmium telluride (CdTe) and copper indium diselenide (CuInGaSe2)
Venue	Presented at the 2006 IEEE 4th World Conference on Photovoltaic Energy Conversion (WCPEC-4) Waikoloa, Hawaii May 7?12, 2006 Conference Paper NREL/CP-520-39838 May 2006
Source	National Renewable Energy Laboratory
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	05/2006

Post Date	11/17/2005
Title	LOW TOXIC PROCESSING OF THIN AND ULTRA-THIN CIGSS ABSORBER SOLAR CELLS
Link	(MS Word 1.6 MB)
Author	N. G. Dhere
Description	CuIn1-xGaxSe2-ySy (CIGSS)/CdS thin-film solar cells were prepared on molybdenum coated glass substrates. A low toxic approach using diethylselenide (DESe) as a selenium source was used for selenization of metallic precursors. A compact and large-grain absorber layer was produced by heating the elemental stack at 475-500oC in the diluted DESe gas. The threshold limit value (TLV) for DESe is 5 times less stringent than that of H2Se. After stabilizing deposition and selenization/sulfurization parameters on a 2.75 ?m thick absorber layer, preliminary experiments were carried out on an ultra-thin (<1 micrometer) absorber to reduce In consumption. Cells with selenide-free chalcopyrite were prepared by sulfurization and a world record Voc of 830 mV was obtained on CuIn1-xGaxS2 (Fig 5). The efficiency (11.99 %) is the highest ever demonstrated using sputtering technique for the metal precursor deposition.
Venue	Solar Technology Review Meeting, Denver, CO 11/7-10/2005, CIS paper from FSEC
Source	FLorida Solar Energy Center
Document Type	Conference Papers (Word document)
Resource Date	11/2005

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	10/18/2005
Title	GROWTH OF CU(INGA)(SES)2 BY THE REACTION OF CU-GA-IN PRECURSORS IN H2SE AND H2S
Link	(MS Word 319 KB)
Authors	G. Hanket, R. W. Birkmire, W. N. Shafarman
Description	Critical issues for the formation of Cu(InGa)(SeS)2 films by the selenization or sulfization reactions of Cu-Ga-In precursor films are investigated. The phases present in the metal precursors after annealing at 450�C were Cu, In, CuIn and Cu9(In1?xGax)4 . Films reacted in hydrogen selenide (H2Se) or hydrogen sulfide (H2S) were characterized and unreacted intermetallic Cu-Ga or Cu-In phases respectively were identified at the back of the films. This indicates a reaction preference of Se with In, and S with Ga. Homogenization of the Ga using a two-step selenization/sulfization process that takes advantage of this reaction preference was confirmed and devices with VOC > 0.64 V and eff. > 13 % were demonstrated
Venue	Solar Program Review 2005
Source	University of Delaware
Document Type	Conference Papers (Word document)
Resource Date	10/2005

Post Date	10/20/2005
Title	PROCESS TOLERANCES IN ROLL-TO-ROLL MANUFACTURING OF CIGS-BASED PHOTOVOLTAICS ON FLEXIBLE SUBSTRATES
Link	(PDF 65 KB) Download Acrobat Reader.
Authors	M. E. Beck, et al.
Description	Two- and three-stage co-evaporation have come to be viewed as benchmark laboratory methods for CuInxGa1-xSe absorber deposition. Although quite successful and relatively easy to implement on a small R&D scale, scale-up to a commercial level proves to be challenging. Yet, large area, continuous manufacturing processes represent the most economically attractive path for thin-film PV commercialization. Large area, continuous processes necessarily differ substantially from laboratory methods, and direct process transfer is not feasible. For implementation of viable, large scale PV manufacturing methods on low-cost substrates it is necessary to understand the tolerance of the established laboratory processes to variations in deposition procedures, as they apply to low-cost roll-to-roll processing onto lightweight stainless steel foils. The success of this approach is impressively demonstrated as Global Solar Energy has achieved 90% production yield and an average production efficiency of 10%, with peak efficiencies exceeding 13% at the large-area cell level.
Venue	DOE Solar Review 2005
Source	Global Solar Energy
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	10/2005

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	08/26/2005
Title	DESIGN CONSIDERATIONS AND IMPLEMENTATION OF VERY-LARGE SCALE MANUFACTURING OF CIGS SOLAR CELLS AND RELATED PRODUCTS
Link	(PDF 1.4 MB) Download Acrobat Reader.
Authors	J. Tuttle, et al.
Description	Discrete CIGS solar cells on flexible metal substrates offer an alternative to wafer-Si based cells. The manufacture of this cell technology additionally offers capital cost, throughput and yield advantages over the manufacture of either wafer-Si or traditional monolithically integrated thin-film modules. Economies of scale and volume can be achieved with the implementation of gigawatt-scale manufacturing. Likewise, vertical integration within the production line to include In refinement, steel substrate finishing, source material synthesis and formation, as well as module packaging materials (either glass and Al or plastic) provide for optimization of cost and supplychain issues.
Venue	Proceedings of the 20th European Photovoltaic Solar Energy Conference and Exhibition ? Barcelona, Spain ? June 2005
Source	DayStar Technologies
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	06/10/2005
Title	THE POTENTIAL FOR HIGH PERFORMANCE IN CIGS SOLAR CELLS: A LABORATORY PERSPECTIVE
Link	(MS Word 566 KB)
Authors	K. Ramanathan, et al.
Description	We present a summary of our work with the preparation of CIGS absorbers which has led to the fabrication of record-efficiency solar cells. The use of the three-stage process in conjunction with composition monitoring facilitates the fabrication of solar cell with efficiencies between 18% and 19.5% for absorber bandgap in the range of 1.1?1.2 eV. It is possible to maintain high open-circuit voltages and high fill factors, and the efficiency gains can be correlated to low diode factors and low junction recombination current. In the second part of this paper, we describe our recent results in reducing absorber thickness and low-temperature deposition. Our preliminary results on absorbers grown from low-purity source materials show promise of reducing the cost of fabricating the absorber.
Venue	20th European PVSC Barcelona, 2005
Source	National Renewable Energy Laboratory
Document Type	Conference Papers (Word document)
Resource Date	06/2005

Post Date	03/03/2005
Title	VARIATIONS OF THIOACETAMIDE TREATMENTS ON CIGS SOLAR CELLS ON STAINLESS STEEL SUBSTRATES ? CORRELATIONS TO DEVICE PERFORMANCE
Link	(PDF 341 KB) Download Acrobat Reader.
Author	W. K. Batchelor
Description	The details of design of experiment (DOE) studies involving thioacetamide treatment performed on Cu(In1-xGax)Se2 (CIGS) deposited on stainless steel are discussed. CIGS films were treated in an aqueous InCl3/thioacetamide (CH3CSNH3) bath varying time, temperature and salt as well as CH3CSNH3 concentration in order to determine the optimum conditions for surface sulfurization. Subsequent device completion employing a CBD CdS buffer was performed under nominally identical conditions. The resulting devices were compared on the basis of deposition conditions including untreated control specimens. Device efficiencies in this study ranged from 6 to 11% and did not show significant improvement over untreated controls. Procedures, results, and possible causes for disagreement with earlier studies are discussed.
Venue	IEEE
Sources	Global Solar; ITN Energy Systems
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	02/2005

Post Date	03/03/2005
Title	TOWARDS THE DEVELOPMENT OF FLEXIBLE CIGS SOLAR CELLS ON POLYMER FILMS WITH EFFICIENCY EXCEEDING 15%
Link	(PDF 1.1 MB) Download Acrobat Reader.
Authors	D. Bremaud, et al.
Description	Development of Cu(In,Ga)Se2 (called CIGS) solar cells on polymers is challenging because of the thermo-physical properties of layers and substrates. CIGS layers of suitable structural and opto-electronic properties should be grown at low temperature (< 500�C) as polyimides tend to degrade at higher deposition temperatures. Additionally, a method for controlled incorporation of an optimum amount of Na in CIGS is needed for highefficiency cells since polyimides do not contain Na. Solar cells were developed on commercially available Upilex foils. CIGS layers were grown by evaporation of elemental Cu, In, Ga and Se at different substrate temperatures. Na from a NaF film was incorporated into CIGS layers with a post-deposition diffusion method that is suitable for in-line production of solar cells. Independent measurements have confirmed 14.1% efficiency under simulated AM1.5 standard test conditions. This is the highest efficiency reported to date for any kind of solar cell grown on polymer films. An average reflectance loss of about 13% was measured for these cells. Application of a commonly used antireflection coating would enable more than 15% efficiency flexible CIGS solar cells on polyimide foils.
Venue	IEEE PVSC
Source	Swiss Federal Institute of Technology
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	02/2005

Post Date	03/03/2005
Title	XPS AND UPS INVESTIGATION OF NH4OH-EXPOSED CU(IN,GA)SE2 THIN FILMS
Link	(PDF 518 KB) Download Acrobat Reader.
Authors	et al., C. L. Perkins
Description	Photoelectron spectroscopy was used to determine the compositional and electronic changes occurring in Cu(In,Ga)Se2 thin films as a result of immersion in aqueous ammonia solution. We find that NH4OH-treated CIGS surfaces are preferentially etched of indium and gallium, resulting in the formation of a thin layer of a degenerate Cu-Se compound that we tentatively identify as Cu2Se. The work function of ammonia-treated samples is found to increase by 0.6 eV relative to as-grown CIGS thin films. The uniformity of chemical bath effects (etching & deposition) was found to be improved by the addition to the bath of a non-ionic surfactant. Initial device results show that the new surfactant-based chemical bath deposition (CBD) method may lead to better and thinner CdS buffer layers.
Venue	IEEE PVSC
Source	National Renewable Energy Laboratory
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	02/2005

Post Date	03/03/2005
Title	THE EFFECT OF MO MORPHOLOGY ON THE PERFORMANCE OF CU(IN,GA)SE2 THIN FILMS
Link	(PDF 1.5 MB) Download Acrobat Reader.
Author	D. C. Fisher
Description	The properties of sputtered and electron-beam evaporated Mo are compared, and the resulting impacts on performance of co-evaporated CIGS devices deposited on each type of back contact are investigated. In past studies, the effect of Mo on Cu(In,Ga)Se2 device efficiency has been attributed largely to control of sodium diffusion from the glass. To verify this hypothesis, sodium-free Al2O3 substrates were utilized. Despite lack of Na in the substrate ? Na was provided as NaF on the Mo layer ? significant differences in device performance between the two types of Mo were observed. Purely resistive effects are ruled out by sheet resistance measurements, and comparison of current-voltage parameters. Negative contributions due to diffusion of harmful impurities from the substrate can be eliminated based on secondary ion mass spectroscopy results. These findings lead to the deduction of device performance dependency on Mo morphology.
Venue	IEEE PVSC
Source	Global Solar
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	02/2005

Post Date	03/22/2005
Title	LBIC ANALYSIS OF THIN-FILM POLYCRYSTALLINE SOLAR CELLS
Link	(MS Word 1.1 MB)
Authors	T. J. Nagle, J. R. Sites
Description	Light-beam-induced-current (LBIC) measurements are providing a direct link between the spatial non-uniformities inherent in thin-film polycrystalline solar cells, such as CdTe and CIGS, and the overall performance of these cells. LBIC is uniquely equipped to produce quantitative maps of local quantum efficiency with relative ease. Spatial resolution of 1 ?m at 1-sun intensity, and return to the same area after other measurements, is routinely achieved. A wavelength range of 638 to 857 nm is available with diode lasers. The LBIC measurements demonstrate that several types of effects that alter cell performance can be traced to specific local-area features. Examples of such effects include defects related to edges, grids, or scribes, spatial variations in alloying, and local changes due to high-temperature stress.
Venue	IEEE PVSC-31
Source	Colorado State University
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	et al., Y. Ueda
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	03/22/2005
Title	QUANTIFICATION OF LOSSES IN THIN-FILM CDS/CDTE SOLAR CELLS
Link	(MS Word 3.5 MB)
Authors	S. Demetsu, J. R. Sites
Description	Quantification of solar cell losses can identify promising pathways for further cell improvements. This paper expands earlier work and applies it specifically to CdS/CdTe cells. For the analysis we have defined four cells: The Target cell is one that should be possible with current industrial processes. The Production cell is typical of today?s production. The Record cell has the highest efficiency (16.5%) reported to date. The Ideal cell has the highest theoretical performance for CdTe. The systematic technique of separating losses, referred to as third level metrics, breaks current, voltage, and fill-factor losses down into their individual loss mechanisms. The losses are expressed both as the deficiency in the specific parameter and as the impact on cell efficiency. The latter allows clear identification of the most significant losses.
Venue	PVSC-31 IEEE
Source	Colorado State University
Document Type	Conference Papers (Word document)
Resource Date	01/2005

Post Date	03/03/2005
Title	ADVANCEMENTS IN FLEXIBLE CIGS MODULE MANUFACTURING
Link	(PDF 1.4 MB) Download Acrobat Reader.
Authors	M. E. Beck, et al.
Description	Roll-to-roll (RTR) manufacturing of consistent photovoltaic (PV) material over 1000-ft long metal foil lots has been realized at Global Solar Energy (GSE). Development of robust sensors and in-situ, real-time process control strategies for all thin-film coating (TFC) steps has enabled Global Solar to achieve manufacturing yields above 90%. In turn, reliable processing conditions enable rapid progress using well-controlled experiments designed for device optimization. Average large-area cell efficiency now exceeds 10%. Efficiency and yield have also been increased at the module level through improved fabrication methods. Flexible modules attain a power-toweight ratio of 40W/kg and aperture area efficiencies exceeding 11%. Real-time and accelerated stress tests investigating product reliability are underway.
Venue	IEEE
Source	Global Solar
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	et al., J. H. Scofield
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	02/07/2005
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	ADVANCEMENTS IN FLEXIBLE CIGS MODULE MANUFACTURING
Link	(PDF 1.4 MB) Download Acrobat Reader.
Authors	M. E. Beck, et al.
Description	Roll-to-roll (RTR) manufacturing of consistent photovoltaic (PV) material over 1000-ft long metal foil lots has been realized at Global Solar Energy (GSE). Development of robust sensors and in-situ, real-time process control strategies for all thin-film coating (TFC) steps has enabled Global Solar to achieve manufacturing yields above 90%. In turn, reliable processing conditions enable rapid progress using well-controlled experiments designed for device optimization. Average large-area cell efficiency now exceeds 10%. Efficiency and yield have also been increased at the module level through improved fabrication methods. Flexible modules attain a power-toweight ratio of 40W/kg and aperture area efficiencies exceeding 11%. Real-time and accelerated stress tests investigating product reliability are underway.
Venue	IEEE PVSC
Source	Global Solar
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	01/2005

Post Date	03/03/2005
Title	CIGS SOLAR MODULES
Link	(PDF 344 KB) Download Acrobat Reader.
Authors	et al., M. Powalla
Description
Venue	IEEE
Sources	Wurth Solar; ZSW
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	2005

Post Date	02/16/2005
Title	THE EFFECT OF MO DEPOSITION CONDITIONS ON DEFECT FORMATION AND DEVICE PERFORMANCE FOR CIGS SOLAR CELLS
Link	(MS Word 63 KB)
Authors	et al., V. Mohanakrishnaswamy
Description	We have studied the effect of native defects on CIGS solar cells on an ongoing basis and recently investigated the role of Na. We modulated access of Na to the growing film by use of Si3N4 blocking layers as well as by varying the Mo thickness and density. Our process is tuned to the level of Na coming from our soda lime glass substrates, however, the role of Na is complex. Collectively the results suggest that one role of Na is that of a catalytic agent for the oxidation of VSe, which is a donor-like defect, to acceptor-like OSe. In simulating the effect of this defect in AMPS we find that its biggest effect on performance is its presence in the junction interface region, and its presence there gives rise to the Jsc ? Voc trade-off that we observe in our experimental data. This results in the efficiency being pinned in the 13 ? 14% range for our deposition process and explains the difficulties we have had in overcoming this mechanism. These insights also indicate the path to overcoming this performance limitation.
Venue	IEEE
Source	University of South Florida, Tampa
Document Type	Conference Papers (Word document)
Resource Date	01/2005

Post Date	03/03/2005
Title	THE EFFECT OF MO MORPHOLOGY ON THE PERFORMANCE OF CU(IN,GA)SE2 THIN FILMS
Link	(PDF 1.5 MB) Download Acrobat Reader.
Authors	et al., D. C. Fisher
Description	The properties of sputtered and electron-beam evaporated Mo are compared, and the resulting impacts on performance of co-evaporated CIGS devices deposited on each type of back contact are investigated. In past studies, the effect of Mo on Cu(In,Ga)Se2 device efficiency has been attributed largely to control of sodium diffusion from the glass. To verify this hypothesis, sodium-free Al2O3 substrates were utilized. Despite lack of Na in the substrate ? Na was provided as NaF on the Mo layer ? significant differences in device performance between the two types of Mo were observed. Purely resistive effects are ruled out by sheet resistance measurements, and comparison of current-voltage parameters. Negative contributions due to diffusion of harmful impurities from the substrate can be eliminated based on secondary ion mass spectroscopy results. These findings lead to the deduction of device performance dependency on Mo morphology.
Venue	IEEE
Source	Global Solar
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	2005

Post Date	02/15/2005
Title	EFFICIENCY LIMITATIONS FOR WIDE-BAND-GAP CHALCOPYRITE SOLAR CELLS
Link	(PDF 309 KB) Download Acrobat Reader.
Authors	M. Gloeckler, J. R. Sites
Description	Wide-band-gap chalcopyrite solar cells, most prominently Cu(In,Ga)Se₂ (CIGS) with high Ga content, have failed over the past years to achieve conversion efficiencies consistent with those achieved with lower-Ga CIGS. Starting from a simple baseline case of a ZnO/CdS/CIGS solar cell, numerical modeling tools were used to investigate the effects of bulk and interface recombination for a broad range of absorber band-gap energies assuming that the Ga/In ratio primarily affects the conduction band. The model predicts that even very small interface recombination velocities limit the open circuit voltage, when the conductionband offset between window and absorber layer is close to zero or is negative. This is the case for CdS/CIGS structures with absorber band gaps above 1.3 - 1.4 eV. The simulations further predict that surface phases or pinning of the Fermi level at the interface can inhibit interface recombination, and hence, lead to an improvement in cell efficiency. Conversion efficiency for all band-gap energies is calculated based on a generic window layer/absorber structure assuming that the band alignment can be arbitrarily chosen. The implication of this work is that although the record CIGS efficiencies have been achieved with CdS window layers, CdS may not be the best window layer for wide-band-gap chalcopyrite solar cells. Our results agree very well with the reported record efficiency for CdS/CuInSe₂, CdS/CdTe, CdS/CuGaSe₂, and CdS/Cu(In,Ga)Se₂.
Venue	EMRS
Source	Colorado State University
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	01/2005

Post Date	09/27/2005
Title	DAMP HEAT STABILITY OF CHALCOPYRITE MINI-MODULES: EVALUATION OF SPECIFIC TEST STRUCTURES
Link	(PDF 77 KB) Download Acrobat Reader.
Authors	J. Klaer, et al.
Description	Damp heat stress (85% relative humidity at 85 �C) has been used to test long term stability of CIS thin film photovoltaic devices. Two CIS absorber types have been examined, CuInS2 and Cu(In,Ga)Se2. Module degradation is dominated by an increase of the series resistance Rs. In order to get information about the ZnO sheet resistance Rsq and the Mo/ZnO contact resistance Rc, which are the most important contributions to Rs, specially designed transmission-line test structures are used. Degradation of Rc strongly depends on the point of time when the second scribe for integrated series connection, P2, is made, while degradation of Rsq is strongly affected by the underlying absorber layer. Module-type solar cells without metal grid and complete mini-modules have been exposed to the same damp heat stress and yield additional information about degradation of other electrical parameters.
Venue	2005 IEEE.
Source	Hahn Meitner
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	03/03/2005
Title	ADVANCEMENTS IN FLEXIBLE CIGS MODULE MANUFACTURING
Link	(PDF 1.4 MB) Download Acrobat Reader.
Authors	M. E. Beck, et al.
Description	Roll-to-roll (RTR) manufacturing of consistent photovoltaic (PV) material over 1000-ft long metal foil lots has been realized at Global Solar Energy (GSE). Development of robust sensors and in-situ, real-time process control strategies for all thin-film coating (TFC) steps has enabled Global Solar to achieve manufacturing yields above 90%. In turn, reliable processing conditions enable rapid progress using well-controlled experiments designed for device optimization. Average large-area cell efficiency now exceeds 10%. Efficiency and yield have also been increased at the module level through improved fabrication methods. Flexible modules attain a power-toweight ratio of 40W/kg and aperture area efficiencies exceeding 11%. Real-time and accelerated stress tests investigating product reliability are underway.
Venue	IEEE
Source	Global Solar
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	2005

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	02/09/2005
Title	PHYSICAL MODES OF THIN-FILM PV DEGRADATION
Link	(PDF 267 KB) Download Acrobat Reader.
Authors	et al., V. G. Karpov
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	03/03/2005
Title	BAND GAP GRADING IN CU(IN,GA)SE2 SOLAR CELLS
Link	(PDF 187 KB) Download Acrobat Reader.
Authors	M. Gloeckler, J. R. Sites
Description	The quaternary system Cu(In,Ga)Se2 (CIGS) allows the band gap of the semiconductor to be adjusted over a range of 1.04 ? 1.67 eV. Using a non-uniform Ga/In ratio throughout the film thickness, additional fields can be built into p-type CIGSbased solar cells, and some researchers have asserted that these fields can enhance performance. The experimental evidence that grading improves device performance, however, has not been compelling, mostly because the addition of Ga itself improves device performance and hence a consistent separation of the grading benefit has not always been achieved. Numerical modeling tools are used in this contribution to show that (1) there can be a beneficial eect of grading, (2) in standard thickness CIGS cells the benefit is smaller than commonly believed, (3) there is also the strong possibility of reduced rather than of increased device performance, and (4) thin-absorber cells derive more substantial benefit.
Venue	Elsevier Science
Source	Colorado State University
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	09/22/2004

Post Date	03/03/2005
Title	INDIUM: SUPPLY, DEMAND & FLAT PANEL DISPLAYS
Link	(MS Word 1.0 MB)
Author	B. O'Neill
Description
Venue	Presented at Minor Metals 2004, London, June 2004
Source	AIM Specialty Materials
Document Type	Conference Papers (Word document)
Resource Date	09/2004

Post Date	02/16/2005
Title	EFFECT OF MAXIMUM CU RATIO DURING THREE-STAGE CIGS GROWTH DOCUMENTED BY DESIGN OF EXPERIMENT
Link	(PDF 248 KB) Download Acrobat Reader.
Authors	M. E. Beck, J. S. Britt, D. C. Fisher, I. L. Repins
Description	The impact of a Cu-rich growth period during threestage CIGS co-evaporation on device performance was examined. Design of experiments was utilized to determine effect magnitudes and statistical significance. It was found that a Cu-rich growth period yields a statistically significant benefit for device performance. By varying film thickness, the number of moles deposited in stage 3 was also included as a variable. The latter did not produce a significant effect on efficiency. Comparison of these conclusions to other studies, and the application to manufacturing, are also discussed.
Venue
Sources	Global Solar; ITN Energy Systems
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	2004

Post Date	02/17/2005
Title	DEVICE MODELING AND SIMULATION OF THE PERFORMANCE OF CU(IN_1-X,GA_X)SE₂
Link	(PDF 367 KB) Download Acrobat Reader.
Authors	et al., J. Song
Description	Device modeling, thin Film solar cell; Cu(In,Ga)Se₂ (CIGS), graded band-gap, open-circuit voltage (V_oc), short-circuit current (I_sc)...
Venue
Source	University of Florida, Gainesville
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	2004

Post Date	02/07/2005
Title	POLYCRYSTALLINE THIN-FILM PHOTOVOLTAIC TECHNOLOGIES: PROGRESS AND TECHNICAL ISSUES
Link	(PDF 370 KB) Download Acrobat Reader.
Author	H. S. Ullal
Description	Polycrystalline thin-film materials based on copper indium diselenide (CuInSe2, CIS) and cadmium telluride (CdTe) are promising thin-film solar cells for various power and specialty applications. Impressive results have been obtained in the past few years for both thin-film copper indium gallium diselenide (CIGS) solar cells and thin-film CdTe solar cells. NCPV/NREL scientists have achieved world-record, total-area efficiencies of 19.3% for a thin-film CIGS solar cell and 16.5% for thin-film CdTe solar cell. A number of technical R&D issues related to CIS and CdTe have been identified. Thin-film power module efficiencies up to 13.4% has been achieved thus far. Tremendous progress has been made in the technology development for module fabrication, and multi-megawatt manufacturing facilities are coming on line with expansion plans in the next few years. Several 40-480 kW polycrystalline thin-film, grid-connected PV arrays have been deployed worldwide. Hot and humid testing is also under way to validate the long-term reliability of these emerging thin-film power products. The U.S. thin-film production (amorphous silicon [a-Si], CIS, CdTe) is expected to exceed 50 MW by the end of 2005.
Venue	PVSEC 19
Source	National Renewable Energy Laboratory
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	2004

Post Date	03/03/2005
Title	TOWARDS THE DEVELOPMENT OF FLEXIBLE CIGS SOLAR CELLS ON POLYMER FILMS WITH EFFICIENCY EXCEEDING 15%
Link	(PDF 1.1 MB) Download Acrobat Reader.
Authors	D. Bremaud, et al.
Description	Development of Cu(In,Ga)Se2 (called CIGS) solar cells on polymers is challenging because of the thermo-physical properties of layers and substrates. CIGS layers of suitable structural and opto-electronic properties should be grown at low temperature (< 500ºC) as polyimides tend to degrade at higher deposition temperatures. Additionally, a method for controlled incorporation of an optimum amount of Na in CIGS is needed for highefficiency cells since polyimides do not contain Na. Solar cells were developed on commercially available Upilex foils. CIGS layers were grown by evaporation of elemental Cu, In, Ga and Se at different substrate temperatures. Na from a NaF film was incorporated into CIGS layers with a post-deposition diffusion method that is suitable for in-line production of solar cells. Independent measurements have confirmed 14.1% efficiency under simulated AM1.5 standard test conditions. This is the highest efficiency reported to date for any kind of solar cell grown on polymer films. An average reflectance loss of about 13% was measured for these cells. Application of a commonly used antireflection coating would enable more than 15% efficiency flexible CIGS solar cells on polyimide foils.
Venue
Source	Swiss Federal Institute of Technology
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	2004

Post Date	02/14/2005
Title	CIGS J-V DISTORTION IN THE ABSENCE OF BLUE PHOTONS
Link	(MS Word 158 KB)
Authors	et al., A. O. Pudov
Description	Common buffer materials used with CuInGaSe₂ (CIGS) absorbers produce conduction-band barriers that may significantly distort the current-voltage curves, especially when short-wavelength photons are excluded from the illumination spectrum. Earlier work documented this effect for CuInSe₂ (CIS) absorbers (band gap near 1.0 eV) with CdS buffers. Higher band-gap (~1.15 eV) CIGS absorbers show little or no distortion with CdS buffer layers. However, wider band-gap (lower electron affinity) ZnS(O,OH) or InS(O,OH) buffers, prepared by chemical-bath deposition, clearly show the J-V distortion. The distortions have a turn-on time constant the order of a minute and turn-off time constant the order of a day, and they correlate with major variations in apparent quantum efficiency measured with varying intensity and spectral content of bias light. The results are consistent with a conduction-band spike barrier that increases with buffer band gap and is larger when the electron concentration in the buffer is small.
Venue	EMRS
Source	Colorado State University
Document Type	Conference Papers (Word document)
Resource Date	2004

Post Date	03/03/2005
Title	THE SHELL SOLAR 245 KW GRID-CONNECTED CIS THIN FILM PV ROOFTOP ARRAY: SYSTEM DESIGN AND FIRST YEAR PERFORMANCE
Link	(PDF 123 KB) Download Acrobat Reader.
Authors	K. Mackamul, R. Wieting
Description	Shell Solar has deployed the world's largest rooftop thin film photovoltaic system, a 245-KW array consisting of 6144 ST40 modules using Shell's innovative copper indium diselenide-based (CIS) technology. Covering nearly 3,000 square meters on its module manufacturing building, the system is arranged in 13 rows wired into 256 module strings of 24 modules each, grid-connected through a 225KW Xantrex inverter. An innovative systems design approach was employed to evaluate a new modular commercial rooftop open-rack type array support structure. Utilizing low cost light gauge cold-formed steel sections, the design minimizes roof penetrations and enables modular design for simplified installation while creating a robust structure capable of withstanding 80 mph winds and zone 4 earthquake resistant. The system is designed for flat roofs (generally defined as pitch less than 2:12, or 2 inches in 12 feet). System design is optimized by analyzing the hourly and seasonal array output with the customer's utility rate schedule. Array tilt and azimuth angles are adjusted to provide the best value proposition to the customer. Additionally, the structure is utilized in a 245 kW CIS thin film installation with the savings and performance logged on a computer via internet.
Venue	IEEE
Source	Shell Solar Industries
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	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	02/04/2005
Title	POLYCRYSTALLINE THIN-FILM PHOTOVOLTAIC TECHNOLOGIES: PROGRESS AND TECHNICAL ISSUES
Link	(MS Word 1.5 MB)
Author	H. S. Ullal
Description	Polycrystalline thin-film materials based on copper indium diselenide (CuInSe2, CIS) and cadmium telluride (CdTe) are promising thin-film solar cells for various power and specialty applications. Impressive results have been obtained in the past few years for both thin-film copper indium gallium diselenide (CIGS) solar cells and thin-film CdTe solar cells. NCPV/NREL scientists have achieved world-record, total-area efficiencies of 19.3% for a thin-film CIGS solar cell and 16.5% for thin-film CdTe solar cell. A number of technical R&D issues related to CIS and CdTe have been identified. Thin-film power module efficiencies up to 13.4% has been achieved thus far. Tremendous progress has been made in the technology development for module fabrication, and multi-megawatt manufacturing facilities are coming on line with expansion plans in the next few years. Several 40-480 kW polycrystalline thin-film, grid-connected PV arrays have been deployed worldwide. Hot and humid testing is also under way to validate the long-term reliability of these emerging thin-film power products. The U.S. thin-film production (amorphous silicon [a-Si], CIS, CdTe) is expected to exceed 50 MW by the end of 2005.
Venue	PVSEC
Source	National Renewable Energy Laboratory
Document Type	Conference Papers (Word document)
Resource Date	2004

Post Date	02/09/2005
Title	NUMERICAL MODELING OF CIGS AND CDTE SOLAR CELLS: SETTING THE BASELINE
Link	(MS Word 669 KB)
Authors	et al., M. Gloeckler
Description	Numerical modeling of polycrystalline thin-film solar cells is an important strategy to test the viability of proposed physical explanations and to predict the effect of physical changes on cell performance. In general, this must be done with only partial knowledge of input parameters. Nevertheless, for consistent comparisons between laboratories, it is extremely useful to have a common starting point, or baseline. We will discuss guidelines that should be considered assigning input parameters for numerical modeling. Consequently specific baseline parameters for CIGS and CdTe are proposed. The modeling results for these baseline cases are presented and it is discussed how the baseline cases serve to describe some of the most important complications that are often found in experimental CIGS and CdTe solar cells.
Venue	IEEE
Source	Colorado State University
Document Type	Conference Papers (Word document)
Resource Date	2004

Post Date	02/09/2005
Title	THE MESOSCALE PHYSICS OF LARGE-AREA PHOTOVOLTAICS
Link	(PDF 252 KB) Download Acrobat Reader.
Authors	et al., V. G. Karpov
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	02/17/2005
Title	EXPLANATION OF LIGHT/DARK SUPERPOSITION FAILURE IN CIGS SOLAR CELLS
Link	(MS Word 445 KB)
Authors	M. Gloeckler, C. Jenkins, J. R. Sites
Description	CIGS solar cells in many cases show a failure of light/dark superposition of their current-voltage (J-V) curves. Such failure generally becomes more pronounced at lower temperatures. J-V measurements under red light may also show an additional distortion, known historically as the "red kink". The proposed explanation is that a secondary barrier results from the conduction band offset between CIGS and the commonly employed CdS window layer. This barrier produces a second diode with the same polarity and in series with the primary photodiode. The secondary-diode barrier height is modified by photoinduced changes of trap occupancy in the CdS layer, hence creating a voltage shift between dark and light conditions. Numerical modeling of the proposed explanation, including a band offset consistent with experimental and theoretical values, gives a very good fit to measured light and dark J-V curves over a wide temperature range. It also predicts the observed difference between illuminated J-V curves with photon energy above the CdS band gap, and those with sub-band-gap illumination...
Venue	MRS, Spring 2003
Source	Colorado State University
Document Type	Conference Papers (Word document)
Resource Date	04/2003

Post Date	02/16/2005
Title	THE EFFECT OF MO MORPHOLOGY ON THE PERFORMANCE OF CU(IN,GA)SE₂ THIN FILMS
Link	(PDF 1.5 MB) Download Acrobat Reader.
Authors	et al., D. C. Fisher
Description	The properties of sputtered and electron-beam evaporated Mo are compared, and the resulting impacts on performance of co-evaporated CIGS devices deposited on each type of back contact are investigated. In past studies, the effect of Mo on Cu(In,Ga)Se₂device efficiency has been attributed largely to control of sodium diffusion from the glass. To verify this hypothesis, sodium-free Al₂O₃ substrates were utilized. Despite lack of Na in the substrate ? Na was provided as NaF on the Mo layer ? significant differences in device performance between the two types of Mo were observed. Purely resistive effects are ruled out by sheet resistance measurements, and comparison of current-voltage parameters. Negative contributions due to diffusion of harmful impurities from the substrate can be eliminated based on secondary ion mass spectroscopy results. These findings lead to the deduction of device performance dependency on Mo morphology.
Venue
Sources	Global Solar; ITN Energy Systems; National Renewable Energy Laboratory
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	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	03/03/2005
Title	CIS THIN FILM MANUFACTURING AT SHELL SOLAR: PRACTICAL TECHNIQUES IN VOLUME MANUFACTURING
Link	(PDF 1.6 MB) Download Acrobat Reader.
Authors	et al., R. Wieting
Description	CIS technologies have emerged from the laboratory. Hand crafted construction of a few small devices has given way to practical methods essential to the continuous manufacturing of large modules in high volumes. This paper surveys the present status of CIS production technology as employed at Shell Solar and reviews in detail a number of the methods developed during the transition to volume manufacturing.
Venue	module making
Source	Shell Solar Industries
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	02/15/2005
Title	NON-VACUUM PROCESSING OF CIGS SOLAR CELLS ON FLEXIBLE POLYMERIC SUBSTRATES
Link	(PDF 186 KB) Download Acrobat Reader.
Authors	et al., V. K. Kapur
Description	Using an ink based non-vacuum process CIGS solar cells were successfully fabricated on a flexible polymeric 'Upilex' substrate. A thin foil (0.001") of 'Upilex' was metallized by sputter deposition of 0.4 �m thick layer of Mo and CIGS solar cells were fabricated on it. 'Upilex' foil along with various device layers on it, withstood the fabrication conditions of ISET's process in which the maximum temperature was raised to 500°C.
Venue	WCPEC Japan
Source	ISET
Document Type	Conference Papers (Adobe Postscript file)
Resource Date	2003

Post Date	02/16/2005
Title	CUIN_XGA_1-XSE₂- THIN FILM SOLAR CELLS USING TRANSPARENT CONDUCTING OXIDE BACK CONTACTS FOR BIFACIAL AND TANDEM SOLAR CELLS
Link	(PDF 336 KB)