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Cadmium Telluride
CdTe thin-film technology is being actively commercialized. CdTe cell efficiencies are over 16% in the laboratory; commercial module efficiencies are likely to be in the 9% range in the first manufacturing plants. Companies have an array of inexpensive options to choose from in CdTe fabrication-there are more than a dozen ways to make 10%—efficient cells.
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Back to Top Conference Papers
| Post Date | 05/30/2008 |
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| Title | THE ROLE OF POLYCRYSTALLINE THIN-FILM PV TECHNOLOGIES IN COMPETITIVE PV MODULE MARKETS |
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| Link | (PDF 351 KB) Download Acrobat Reader. |
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| Authors | B. Von Roedern, H. S. Ullal |
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| 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. |
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| Venue | Presented at the 33rd IEEE PVSC Conference, San Diego, CA 05/12-16/2008 |
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| Source | National Renewable Energy Laboratory |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 05/2008 |
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| Post Date | 09/28/2007 |
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| Title | THIN FILM CIGS AND CDTE PHOTOVOLTAIC TECHNOLOGIES: COMMERCIALIZATION, CRITICAL ISSUES, AND APPLICATIONS |
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| Link | (PDF 725 KB) Download Acrobat Reader. |
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| Authors | H. S. Ullal, B. Von Roedern |
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| 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. |
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| Venue | 22nd EC PVSEC, Milano, Italy Sep 3-7, 2007, paper presented |
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| Source | National Renewable Energy Laboratory |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 09/2007 |
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| Post Date | 04/30/2007 |
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| Title | OUTDOOR MONITORING AND HIGH VOLTAGE BIAS TESTING OF THIN FILM PV MODULES |
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| Link | (MS Word 64 KB) |
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| Author | N. G. Dhere |
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| 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. |
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| Venue | DOE Solar Technology Review Meeting, Denver, CO, 4/17-19/2007 |
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| Source | FLorida Solar Energy Center |
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| Document Type | Conference Papers (Word document) |
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| Resource Date | 03/2007 |
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| Post Date | 04/30/2007 |
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| Title |   VOLTAGE DEFICIT IN THIN-FILM POLYCRYSTALLINE SOLAR CELLS |
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| Link | (MS Word 46 KB) |
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| Author | J. R. Sites |
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| 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. |
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| Venue | DOE Solar Technology Review Meeting, Denver, CO 4/17-17/2007 |
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| Source | Colorado State University |
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| Document Type | Conference Papers (Word document) |
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| Resource Date | 03/2007 |
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| Post Date | 10/26/2006 |
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| Title | BOS COST SAVINGS NEEDS AND POTENTIAL FOR LARGE SCALE GROUND BASED PV SYSTEMS UNTIL 2010 |
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| Link | (PDF 495 KB) Download Acrobat Reader. |
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| Author | M. Bachler |
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| 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. |
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| Venue | Dresden World Conference |
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| Source | Phonix SonnenStrom AG |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 09/2006 |
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| Post Date | 06/14/2006 |
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| Title | CDTE PHOTOVOLTAICS: LIFE CYCLE ENVIRONMENTAL PROFILE AND COMPARISONS |
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| Link | (PDF 210 KB) Download Acrobat Reader. |
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| Author | V. Fthenakis |
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| Description | We discuss the emissions of cadmium throughout all the life stages of CdTe PV modules, from extracting, refining, and purifying the raw materials to producing, using, and disposing or recycling of the modules. Then, we compare these emissions with those in the life cycle of three different types of crystalline Si PV modules. The energy requirement and energy pay back times (EPBT) of CdTe PV modules is considerably shorter than that of crystalline Si modules, although the latter exhibit higher efficiencies. This difference is primarily due to the energy used to process silicon, a fraction of which is derived from fossil fuels, inevitably producing Cd and many other heavy-metal emissions. |
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| Venue | Presented at the European Material Research Society Meeting |
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| Source | N/A |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 06/2006 |
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| Post Date | 05/18/2006 |
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| Title | HIGH-EFFICIENCY CDTE AND CIGS THIN-FILM SOLAR CELLS: HIGHLIGHTS AND CHALLENGES |
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| Link | (MS Word 602 KB) |
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| Authors | R. Noufi, K. Zweibel |
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| 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. |
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| Venue | WPEC4, Hawaii |
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| Source | National Renewable Energy Laboratory |
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| Document Type | Conference Papers (Word document) |
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| Resource Date | 05/2006 |
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| Post Date | 05/22/2006 |
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| Title | TECHNOLOGY CHOICE AND THE COST REDUCTION POTENTIAL OF PHOTOVOLTAICS |
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| Link | (PDF 116 KB) Download Acrobat Reader. |
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| Authors | J. E. Trancik, K. Zweibel |
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| 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. |
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| Venue | Trancik and Zweibel, WCPEC-4 2006 |
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| Sources | National Renewable Energy Laboratory; Santa Fe Institute |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 05/2006 |
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| Post Date | 11/07/2006 |
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| Title | THE RELATIONSHIP OF CDS/CDTE CELL BAND PROFILES TO J-V CHARACTERISTICS AND BIAS-DEPENDENT QUANTUM EFFICIENCY |
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| Link | (PDF 1.6 MB) Download Acrobat Reader. |
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| Author | A. Fahrenbruch |
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| Description |
AMPS models of two extreme profiles are discussed here as illustrations: an n/i/p junction, where V bi is mainly supported by charge at the contacts, and an n/p junction, where Vbi is supported by charge in the bulk CdTe within the absorber
There are several general pathways to increasing the efficiency of CdS/CdTe cells. Since J sc is close to its limit, those with the most potential yield involve increasing the cell voltage at the maximum power point (Vmax). These are discussed here in a theoretical way to view trends, allowing that they may be very difficult or impossible to realize in practice. One pathway is by increasing the net negative charge in the CdTe by ?p-type doping.? Another is by increasing the minority carrier lifetime (tn) by, for example, control of impurities, reducing growth rate, and/or changing the micro-stoichiometry. These two pathways deal with bulk materials properties. A third pathway is by decreasing the back-contact barrier height Fbc and the recombination there, both interface properties. Many other pathways are less risky and more practical including: thinner windows and/or absorber layers, increasing the window band gap, and optical optimization.
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| Venue | 4th WCPEC ((IEEE PVSC), Hawaii 05/2006 paper |
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| Source | Colorado State University |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 05/2006 |
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| Post Date | 09/19/2006 |
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| Title | HOW CDTE SOLAR CELLS OPERATE: DETERMINING COLLECTION USING BIFACIAL DEVICE CHARACTERIZATION |
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| Link | (PDF 113 KB) Download Acrobat Reader. |
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| Authors | D. Desai, S. S. Hegedus, B. E. McCandless, R. W. Birkmire, K. D. Dobson, D. Ryan |
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| Description |
The results presented in this paper provide a quantitative understanding of minority carrier transport parameters in CdTe based photovoltaic devices. We have demonstrated that bifacial device characterization is a valuable and efficient tool for analysis of the primary transport parameters and allows separation of the primary CdS/CdTe junction from the back contact. We conclude that for standard front illumination, the fill factor (FF) and spectral response from front (SR F) are limited by voltage dependent collection and L is nearly irrelevant. However, spectral response from back illumination (SRB) is limited by diffusion through the bulk to the depletion edge. W and L were derived by extensive numerical analysis of SRB data. The values of W obtained were independently confirmed by CV measurements, thus validating the numerical model and the analysis procedure. The blocking contact usually observed in CdTe devices is photoconductive and can be effectively eliminated by illumination. This blocking contact barrier has no effect on Voc. |
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| Venue | IEC, U. Delaware, paper given at 4th WCPEC (Hawaii, 2006) |
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| Source | University of Delaware |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 05/2006 |
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| Post Date | 08/25/2006 |
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| Title | POLYCRYSTALLINE THIN-FILM PHOTOVOLTAICS: FROM THE LABORATORY TO SOLAR FIELDS |
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| Link | (PDF 682 KB) Download Acrobat Reader. |
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| Authors | B. Von Roedern, H. S. Ullal, K. Zweibel |
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| 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) |
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| 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 |
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| Source | National Renewable Energy Laboratory |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 05/2006 |
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| Post Date | 10/20/2005 |
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| Title | LIFE CYCLE ANALYSIS OF PHOTOVOLTAIC SYSTEMS |
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| Link | (PDF 144 KB) Download Acrobat Reader. |
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| Author | V. Fthenakis |
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| Description | Life Cycle Analyses (LCA) at BNL show that: i) The BOS of an optimized installation has an energy payback time (EPBT) of only 0.4 years for average US insolation, which is 70% lower than previously reported estimates. ii) The EPBT of CdTe modules produced and used in the U.S. is 0.85 years. iii) The life-cycle CO2 emissions of the nuclear fuel cycle in the U.S. are about the same as those in the PV cycle; this contrasts European studies showing CO2 emissions from nuclear to be 10 lower than those from PV. |
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| Venue | Solar Program Review Meeting 2005 |
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| Source | Brookhaven National Laboratory |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 10/2005 |
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| Post Date | 10/20/2005 |
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| Title | A REVIEW OF RISKS IN THE SOLAR ELECTRIC LIFE-CYCLE |
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| Link | (PDF 642 KB) Download Acrobat Reader. |
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| Authors | V. Fthenakis, H. C. Kim |
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| 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. |
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| Venue | Brussels 2005 |
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| Source | Brookhaven National Laboratory |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 10/2005 |
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| Post Date | 06/29/2005 |
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| Title | NREL PAPERS FOR THE PVSC IN ORLANDO, 2005 |
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| Link | (MS Word 41 KB) |
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| Author | N/A |
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| Description | Links to about 20 papers in CIS, CdTe, a-Si, thin Si and reliability. |
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| Venue | |
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| Source | National Renewable Energy Laboratory |
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| Document Type | Conference Papers (Word document) |
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| Resource Date | 06/2005 |
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| Post Date | 06/14/2005 |
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| Title | ENERGY AND LIFE CYCLE ASSESSMENT OF THIN FILM CDTE PHOTOVOLTAIC MODULES |
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| Link | (PDF 360 KB) Download Acrobat Reader. |
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| Author | M. Raugei |
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| Description | topic of this paper is the Life Cycle Assessment (LCA) of modern CdTe PV modules. The analysis was performed within the framework of the European research project PVACCEPT, and is based on actual
production data provided by the former project partner ANTEC Solar GmbH. This latter point makes the present LCA especially worthy of attention as a preliminary indication of the future environmental impact that the upscaling of CdTe module production may entail. The analysis is performed according to the recommendations of ISO norms 14040 and updates, and makes use of an original multi-criteria approach named SUMMA. The performance of the analysed CdTe system is also compared to other examples of advanced PV systems based on
different technologies (CIS and mc-Si), which were also part of the PVACCEPT project. Results clearly show an overall very promising picture for CdTe technology, which is found to be characterised by
favourable environmental impact indicators (e.g. 60g(abiotic matter)/kWh, 32 g(CO2-eq)/kWh and energy payback of 0.9 yrs. |
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| Venue | 20th EU PVSC Barcelona |
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| Source | University of Siena |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 06/2005 |
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| Post Date | 06/14/2005 |
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| Title | EMPIRICAL TUNING METHODOLOGY FOR AS AND CL DOPING OF MOCVD GROWN CDTE |
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| Link | (PDF 192 KB) Download Acrobat Reader. |
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| Author | V. Barrioz |
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| Description | Photovoltaic solar cells based on CdTe absorbers are still showing comparitively high efficiencies, currently at 16.5%. However, these cells rely on CdCl2 treatments which are not fully understood and constrainflexibility over cell design. In this work, the effect of controlled arsenic and chlorine doping will be discussed as a potential alternative to CdCl2 treatments. The CdTe/CdS structures were grown by MOCVD onto commercial ITO/glass substrates. Numerous growth and post-growth parameters were varied such as; the II:VI precursor ratios, the substrate temperatures (Tsub) and the in situ post-growth annealing ambient gas (H2 or N2). A strategic statistical design of experiments, the Taguchi matrix method, was used, to establish the best combination of material parametersfor photovoltaic solar cell. High arsenic doping concentrations were needed to achieve a good photo-response in the test cells with a Jsc = 24.3 mA.cm-2, but the cell efficiency was limited by other parameters Voc = 0.55 V; FF = 40.9 %. The other main parameters increasing the cell efficiency were the in situ CdCl2 treatment and substrate temperatures of 315oC and 390oC during the growth of CdS and CdTe respectively. Any post-growth annealing at 500oC damaged considerably the photocurrent response. The method has been successful in showing rapid progress with a new approach, using 16 material and process parameters, in just 36 experiments, for achieving acceptable PV test cells. |
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| Venue | 20th EU PVSC Barcelona |
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| Source | University of Wales |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 06/2005 |
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| Post Date | 06/13/2005 |
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| Title | IMPLICATIONS OF EUROPEAN ENVIRONMENTAL LEGISLATION FOR PHOTOVOLTAIC SYSTEMS |
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| Link | (PDF 434 KB) Download Acrobat Reader. |
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| Authors | M. J. De Wild-Scholten, K. Wambach, E. A. Alsema, A. Jager-Waldau |
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| 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. |
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| Venue | 20th European PVSC Barcelona |
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| Sources | Deutsche Solar; Energy Research Centre of the Netherlands |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 06/2005 |
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| Post Date | 05/09/2005 |
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| Title | CURRENT TRANSIENTS IN CDS/CDTE SOLAR CELLS |
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| Link | (PDF 194 KB) Download Acrobat Reader. |
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| Author | A. Fahrenbruch |
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| Description | Current transient responses to voltage and illumination steps are investigated to clarify the mechanisms involved in carrier transport in CdS/CdTe cells. For most cells, the response to a dark, forward-bias step after a long dark soak at zero bias is a current growth curve For one such
cell, the magnitude of the transient is ¡Ö 22% of the starting value with half of the growth occurring within ¡Ö 5 sec, the other half requiring 1000's of seconds. The effect is completely reversible and a mirror-image decay curve at zero bias after dark bias-on equilibration can be measured. Similarly, a complex of growth and decay curves are observed on application of illumination steps with constant bias. Similar transients have been observed by McMahon [1] and del Cueto et al. [2]. This is a survey of these effects in cells from three different fabricators. These transients, with varying magnitudes and directions, were seen in all the cells studied.
In general, the better the cell, the smaller the magnitudes of the transients. They range from changes by factors of 10 for pathological cells to subtle transients of 1-2% in excellent cells. Beside the important implications these transients have for accurate measurements of cell efficiency and stability, they provide clues about the carrier transport mechanisms.. One of the mechanisms proposed involves the occupation of deep donor traps with small hole cross sections, changing their recombination kinetics. The second hypothesis involves the modulation of the junction barrier profile by changing the charge on deep acceptors and donors by carrier trapping,
leading to a change in the effective junction barrier height. A third involves defect mutation such as that of [Cui] donors into [VCd]. |
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| Venue | Presented at the MRS Spring Meeting 3/28-4/1/2005, San Francisco REVISED 4/9/2005 |
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| Source | Colorado State University |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 04/09/2005 |
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| Post Date | 04/05/2005 |
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| Title | PHYSICS OF CDTE PHOTOVOLTAICS: FROM FRONT TO BACK |
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| Link | (PDF 332 KB) Download Acrobat Reader. |
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| Authors | et al., V. G. Karpov |
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| Description | We discuss physical mechanisms underlying the performance and stability of CdTe based thin-film PV. The processes in (i) photovoltaic junction, (ii) back contact, (iii) nonuniformities, (iv) grain boundaries, and (v) light-induced degradation are addressed including their interactions. The physics of thin film PV turns out to be quite different from that of crystalline PV. High surface-volume ratio and lack of crystallinity result in strong interfacial effects, lateral nonuniformities, and shunting-like and adhesion instabilities in thin film structures. This paper is aimed at presenting a ?big picture?; also, it suggests practical ways of improving thin-film PV. |
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| Venue | MRS Spring Meeting 2005, March 28 ? April 1, San Francisco, |
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| Source | University of Toledo |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 03/28/2005 |
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| Post Date | 03/22/2005 |
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| Title | LBIC ANALYSIS OF THIN-FILM POLYCRYSTALLINE SOLAR CELLS |
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| Link | (MS Word 1.1 MB) |
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| Authors | T. J. Nagle, J. R. Sites |
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| 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. |
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| Venue | IEEE PVSC-31 |
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| Source | Colorado State University |
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| Document Type | Conference Papers (Word document) |
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| Resource Date | 01/2005 |
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| Post Date | 02/11/2005 |
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| Title | LIFE CYCLE ASSESSMENT OF PHOTOVOLTAICS: PERCEPTIONS, NEEDS, AND CHALLENGES |
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| Link | (PDF 222 KB) Download Acrobat Reader. |
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| Authors | E. A. Alsema, M. J. De Wild-Scholten, V. Fthenakis |
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| 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. |
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| Venue | IEEE Photovoltaic Specialistis Conference, Jan. 3-7, 2005, Orlando, FL |
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| Sources | Brookhaven National Laboratory; Energy Research Centre of the Netherlands; Utrecht University |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 01/2005 |
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| Post Date | 02/15/2005 |
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| Title | EARLY PERFORMANCE FOR THE ROOF-MOUNTED, 20-KW THIN FILM CDTE PV-ARRAY AT JASPER RIDGE |
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| Link | (PDF 364 KB) Download Acrobat Reader. |
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| Authors | et al., J. H. Scofield |
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| 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. |
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| Venue | IEEE PVSC |
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| Source | Oberlin College |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 01/2005 |
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|
| Post Date | 03/22/2005 |
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| Title | QUANTIFICATION OF LOSSES IN THIN-FILM CDS/CDTE SOLAR CELLS |
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| Link | (MS Word 3.5 MB) |
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| Authors | S. Demetsu, J. R. Sites |
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| 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. |
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| Venue | PVSC-31 IEEE |
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| Source | Colorado State University |
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| Document Type | Conference Papers (Word document) |
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| Resource Date | 01/2005 |
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|
| Post Date | 07/15/2005 |
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| Title | QUANTIFICATION OF LOSSES IN THIN FILM CDS/CDTE CELLS |
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| Link | (PDF 288 KB) Download Acrobat Reader. |
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| 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. R- |
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| Venue | PVSC Orlando, FL 2005 |
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| Source | Colorado State University |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 01/2005 |
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|
| Post Date | 02/15/2005 |
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| Title | ANALYTICAL RESULTS OF OUTPUT RESTRICTION DUE TO THE VOLTAGE INCREASING OF POWER DISTRIBUTION LINE IN GRID-CONNECTED CLUSTERED PV SYSTEMS |
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| Link | (PDF 2.4 MB) Download Acrobat Reader. |
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| Authors | et al., Y. Ueda |
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| 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. |
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| Venue | IEEE PVSC |
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| Source | Tokyo University |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 01/2005 |
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|
| Post Date | 02/14/2005 |
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| Title | EARLY PERFORMANCE FOR THE ROOF-MOUNTED, 20-KW THIN FILM CDTE PV-ARRAY AT JASPER |
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| Link | (PDF 354 KB) Download Acrobat Reader. |
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| Author | J. H. Scofield |
|---|
| Description | 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, elevated 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. |
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| Venue | IEEE PVSC |
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| Source | Oberlin College |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 01/2005 |
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|
| Post Date | 02/07/2005 |
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| Title | THE ROLE OF POLYCRYSTALLIN THIN-FILM PV TECHNOLOGIES FOR ACHIEVING MID-TERM MARKET-COMPETITIVE PV MODULES |
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| Link | (MS Word 123 KB) |
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| Authors | B. Von Roedern, K. Zweibel |
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| 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. |
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| Venue | IEEE PV Specialists Conference, 2004 |
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| Source | National Renewable Energy Laboratory |
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| Document Type | Conference Papers (Word document) |
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| Resource Date | 01/2005 |
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|
| Post Date | 02/09/2005 |
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| Title | TRANSPARENT CONTACT DEVELOPMENT FOR CDSE TOP CELLS IN HIGH EFFICIENCY TANDEM STRUCTURES |
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| Link | (MS Word 65 KB) |
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| Authors | et al., P. Mahawala |
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| Description | developing transparent contact/CdSe/transparent contact structures deposited on glass/SnO2:F. With these transparent structures we have demonstrated record Jsc's of 17.4 mA/cm2. SnO2 serves as the n contact, and the p contact is ZnSe:Cu. These structures have also exhibited sub band gap transmission of 80%. We have evaluated ZnO and CdS as alternative n contacts and ZnTe as an alternative p contact. Voc's of only 300 mV are being attained with ZnSe:Cu because its Fermi level seems to be near the middle of the band gap of CdSe in spite of favorable valence band alignment. However, using ZnTe:Cu as the p contact we have achieved Voc's up to 575 mV, a new high. |
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| Venue | IEEE |
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| Source | University of South Florida, Tampa |
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| Document Type | Conference Papers (Word document) |
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| Resource Date | 11/2004 |
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|
| Post Date | 02/08/2005 |
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| Title | CONSISTENT PROCESSING AND LONG TERM STABILITY OF CDTE DEVICES |
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| Link | (PDF 1.4 MB) Download Acrobat Reader. |
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| Authors | K. L. Barth, R. A. Enzenroth, W. S. Sampath |
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| Description | A technology for processing of thin film CdS/CdTe devices has been developed in our laboratory. This inline, continuous, pilot system enables unique processing steps and conditions not available with batch processing and allows the fabrication of a large number of devices. Results from the pilot scale system are applicable to systems processing larger areas. |
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| Venue | IEEE |
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| Source | Colorado State University |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 10/2004 |
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|
| Post Date | 02/08/2005 |
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| Title | THERMAL ADMITTANCE SPECTROSCOPY STUDY: PRELIMINARY OBSERVATIONS OF A MEYER-NELDEL RELATIONSHIP IN CDTE DEVICES |
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| Link | (PDF 689 KB) Download Acrobat Reader. |
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| Authors | K. L. Barth, R. A. Enzenroth, W. S. Sampath |
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| Description | CdTe analysis. |
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| Venue | IEEE |
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| Source | Colorado School of Mines, Golden, CO |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 10/2004 |
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|
| Post Date | 02/04/2005 |
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| Title | STUDY OF POTENTIAL COST REDUCTIONS RESULTING FROM SUPER-LARGE-SCALE MANUFACTURING OF PV MODULES |
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| Link | (MS Word 112 KB) |
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| Authors | R. Arya, M. Keshner |
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| Description | Short version of multi-GW production report |
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| Venue | NREL Solar Review |
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| Source | Hewlett Packard |
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| Document Type | Conference Papers (Word document) |
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| Resource Date | 10/2004 |
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|
| Post Date | 02/09/2005 |
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| Title | HIGH THROUGHPUT PROCESSING OF CDTE/CDS SOLAR CELLS |
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| Link | (MS Word 596 KB) |
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| Authors | et al., B. E. McCandless |
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| Description | Methods for achieving high throughput and materials yield in processing >13% efficient CdTe thin film solar cells are demonstrated, with emphasis on emiconductor deposition and post-deposition processing. Chemical surface deposition was used to deposit uniform 100 cm2 area CdS films 50 nm thick at 0.2 nm/sec, with >80% tilization of solvated Cd species. Vapor transport at 20 Torr was used to deposit dense CdTe films, 1-7 ?m thick, onto CdS-coated substrates with >50% utilization in an unbaffled system. Uniform films have been deposited with translation at up to 12 cm/min and static equivalent growth rate >80 ?m/min. Vapor CdCl2 post-deposition treatments yielded solar cells with AM1.5 conversion efficiency >13% for 6 mm thick CdTe and >8% for 1 mm thick CdTe. |
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| Venue | IEEE PVSC |
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| Source | University of Toledo |
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| Document Type | Conference Papers (Word document) |
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| Resource Date | 10/2004 |
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|
| Post Date | 02/08/2005 |
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| Title | THE IMPROVED INTRINSIC STABILITY OF CDTE POLYCRYSTALLINE THIN FILM DEVICES |
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| Link | (PDF 137 KB) Download Acrobat Reader. |
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| Authors | D. Albin, et al. |
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| Description | Parametric studies of CdS/CdTe device stability. |
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| Venue | DOE/NREL Solar Review 2004 |
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| Source | National Renewable Energy Laboratory |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 10/2004 |
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|
| Post Date | 02/09/2005 |
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| Title | PHYSICAL MODES OF THIN-FILM PV DEGRADATION |
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| Link | (PDF 267 KB) Download Acrobat Reader. |
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| Authors | et al., V. G. Karpov |
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| 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. |
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| Venue | IEEE |
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| Source | University of Toledo |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 10/2004 |
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|
| Post Date | 02/10/2005 |
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| Title | CHARACTERISTICS OF CDTE FILMS OF DIFFERENT COMPOSITIONSFABRICATED BY CMBD |
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| Link | (MS Word 965 KB) |
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| Authors | et al., T. M. Razykov |
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| Description | CdTe films with near stoichiometric compositions and cadmium-rich compositions were fabricated by a novel low-cost chemical molecular beam deposition (CMBD) technique at atmospheric pressure under hydrogen or nitrogen gas flow. X-ray diffraction analysis and scanning electron microscopy studies show different grain growth by CMBD depending on the composition of samples. Those grown with cadmium rich compositions were of poor quality with large discontinuous island structures. On the other hand, samples grown with near stoichiometric compositions were polycrystalline with large grain size and uniform thickness. Additionally, films grown under nitrogen flow contained a cadmium tellurium oxide phase while those grown under hydrogen did not. |
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| Venue | 31st IEEE PVSC |
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| Source | Uzbek Academy of Sciences |
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| Document Type | Conference Papers (Word document) |
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| Resource Date | 10/2004 |
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|
| Post Date | 02/09/2005 |
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| Title | THE INFLUENCE OF VARIOUS FRONT CONTACT MATERIALS ON THE PERFORMANCE OF CDTE SOLAR CELLS |
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| Link | (MS Word 201 KB) |
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| Authors | et al., R. Mamazza |
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| Description | The use of a resistive, or buffer, layer in the front con-tact structure of CdTe solar cells has been known to improve solar cell performance, in particular when the CdS thickness is relatively small. This paper reviews the performance of CdTe solar cells fabricated on various front contact bi-layer combinations. Conductive (low-r) trans-parent oxides utilized for this work include SnO2:F, Cd2SnO4 and ITO; resistive (high-r) transparent oxides include SnO2, In2O3, and Zn2SnO4. All high-r layers were found to be effective within a range of processing condi-tions and process/device characteristics. Buffer layers of Zn-Sn-O appear to be the most promising high-? films for the fabrication of CdTe cells with small CdS thickness without compromising the VOC and FF. |
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| Venue | IEEE PVSC |
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| Source | University of South Florida, Tampa |
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| Document Type | Conference Papers (Word document) |
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| Resource Date | 10/2004 |
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|
| Post Date | 02/08/2005 |
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| Title | INTRODUCTION OF CU IN CDS AND ITS EFFECT ON CDTE SOLAR CELLS |
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| Link | (MS Word 130 KB) |
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| Authors | K. Barri, et al. |
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| Description | The use of copper during the fabrication of CdTe solar cells is a common feature for nearly all processing schemes developed for these devices. Copper is typically introduced in CdTe during the application of the back electrode, to enhance device performance by facilitating the formation of an ohmic back contact. However, Cu has also been associated with observed instability in CdTe. For this work, although Cu was utilized during the cell fabrication process, it was eliminated from the back contact formation step, and instead introduced in the CdS film prior to the deposition of the CdTe. The only fabrication step, where Cu was intentionally introduced, was subsequent to the CdS deposition. Both plain graphite and Sb2Te3/Mo were used as back contacts. Solar cell results suggested that ohmic contacts to CdTe can be attained with undoped graphite as the back electrode. For devices contacted with plain graphite VOC's and FF's in the range of 800-830 mV and 63-67% have been obtained. For Sb2Te3-contacted cells, the incorporation of Cu in CdS has lead to a significant increase in performance even though a back barrier was present in these cells. |
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| Venue | IEEE |
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| Sources | National Renewable Energy Laboratory; University of South Florida, Tampa |
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| Document Type | Conference Papers (Word document) |
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| Resource Date | 10/2004 |
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|
| Post Date | 02/09/2005 |
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| Title | RF SPUTTER ETCH AS A SURFACE CLEANING PROCESS FOR CDTE SOLAR CELLS |
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| Link | (MS Word 171 KB) |
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| Authors | et al., V. Viswanathan |
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| Description | The primary objective of this work is to investigate the potential of an alternative dry, vacuum-based process, as a surface modification step for CdTe prior to the application of the back contact electrode. RF-sputter etch has been used as an alternative surface cleaning process. The process was optimized for the type of etchant gas, pressure, time, and sputter power. Solar cells exhibited VOC's greater than 830 mV and FF's in the high 60's. This performance demonstrates the potential of this process for the development of an all-dry vacuum based CdTe technology. |
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| Venue | IEEE |
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| Source | University of South Florida, Tampa |
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| Document Type | Conference Papers (Word document) |
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| Resource Date | 10/2004 |
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|
| Post Date | 02/09/2005 |
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| Title | THE STATUS OF AND CHALLENGES IN CDTE THIN-FILM SOLAR-CELL TECHNOLOGY |
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| Link | (PDF 160 KB) Download Acrobat Reader. |
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| Author | A. Compaan |
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| Description | Polycrystalline CdTe thin- film solar cells have shown high potential for low cost, large-area module fabrication. But successful large-scale commercial production has been elusive. Fabrication of the basic n-CdS / p-CdTe heterojunction is possible by a wide variety of methods, including close-spaced sublimation, vapor-transport deposition, electrodeposition, chemical bath deposition, and magnetron sputtering. An overview of these methods is presented as well as the role of the postdeposition "activation" treatment using CdCl2. |
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| Venue | Spring 2004 MRS Symp. Amorphous and Nanocrystalline Silicon Science and Technology Proceedings to appear as MRS Symp. Proc. |
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| Source | University of Toledo |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 06/2004 |
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|
| Post Date | 02/11/2005 |
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| Title | EXPERIMENTAL INVESTIGATION OF EMISSIONS AND REDISTRIBUTION OF ELEMENTS IN CDTE PV MODULES DURING FIRES |
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| Link | (PDF 246 KB) Download Acrobat Reader. |
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| Authors | et al., V. Fthenakis |
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| Description | This study is based on glass-glass CdTe PV modules which are the only ones in the market. Pieces of commercial CdTe photovoltaic (PV) modules, sizes 3.8 cm by 30.5 cm, were heated to temperatures up to 1100ºC to simulate exposure to residential and commercial building fires. The temperature rate and duration in these experiments were defined according to standard UL and ASTM test protocols. Three different types of analysis were performed: measurements of sample weight loss as a function of temperature; analyses of Cd in the fire emissions; and analysis of Cd distribution in the molten glass, using Synchrotron x-ray fluorescence microprobe. It was found that a small amount of cadmium compounds (0.4 to 0.6% of the Cd content) was carried to the edges by the flow of EVA decomposition products. The pathway for this loss was through the perimeter of the sample before the two sheets of glass fused together. In actual size PV modules, the ratio of perimeter to area is 13.5 times smaller; thus the actual Cd loss during fires would be insignificant (<0.04% of the Cd content). |
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| Venue | European PV Solar Energy Conference, Paris, France, June 7-11, 2004; Paper 5BV.1.32 |
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| Source | Brookhaven National Laboratory |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 06/2004 |
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|
| Post Date | 02/09/2005 |
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| Title | STABILIZATION OF HIGH-EFFICIENCY CDTE PHOTOVOLTAIC MODULES IN CONTROLLED INDOOR LIGHT SOAKING |
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| Link | (PDF 330 KB) Download Acrobat Reader. |
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| Authors | D. Cunningham, J. A. del Cueto, J. Pruett |
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| Description | The performance and stabilization of large-area, high-efficiency 9%, CdTe photovoltaic (PV) modules maintained under controlled light-soaking nominally at 800 Watts/m2 irradiance and 65°C module temperature are investigated. Degradation of module performance occurs predominantly in the first few hundred hours of exposure under these conditions; these symptoms included losses in fill factor (FF), open-circuit voltage (Voc), and short-circuit current (Isc), which amount to between 7% and 15% total loss in performance. Higher stabilized performance was achieved with lower copper content in the back contact. Transient effects in module V... |
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| Venue | |
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| Sources | BP Solar; National Renewable Energy Laboratory |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 2004 |
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|
| Post Date | 02/04/2005 |
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| Title | POLYCRYSTALLINE THIN-FILM PHOTOVOLTAIC TECHNOLOGIES: PROGRESS AND TECHNICAL ISSUES |
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| Link | (MS Word 1.5 MB) |
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| 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. |
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| Venue | PVSEC |
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| Source | National Renewable Energy Laboratory |
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| Document Type | Conference Papers (Word document) |
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| Resource Date | 2004 |
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|
| Post Date | 02/10/2005 |
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| Title | QUANTUM EFFICIENCY OF CDTE SOLAR CELLS IN FORWARD BIAS |
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| Link | (PDF 234 KB) Download Acrobat Reader. |
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| Authors | M. Gloeckler, J. R. Sites |
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| Description | The quantum efficiency of a CdS/CdTe solar cell is measured under forward voltage, the measurement is likely affected by several factors including (1) the voltage dependence of the collection efficiency, (2) series resistance of the cell and instrumentation, (3) the electrical barrier of the back contact, (4) photoconductive effects in the CdS and CdTe, and (5) any secondary barrier in the primary junction. Each of these effects has a distinct signature, but without careful attention to these signatures, misinterpretation is possible and perhaps common. The approach here is to numerically simulate effect (1), and then progressively add effects (2), (3), (4), and (5). In each case, we show the characteristic signature of the apparent quantum efficiency when voltage is varied, we discuss the effect of bias light on the quantum efficiency measurement, we compare when possible with analytical modeling, and we show the impact of each effect on the cell's current-voltage curves, particularly the light/dark crossover. Although the presentation will be specific to CdTe cells, the principles should at least in part apply to other solar cells as well. |
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| Venue | Paris 2004 |
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| Source | Colorado State University |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 2004 |
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|
| Post Date | 02/09/2005 |
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| Title | NUMERICAL MODELING OF CIGS AND CDTE SOLAR CELLS: SETTING THE BASELINE |
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| Link | (MS Word 669 KB) |
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| Authors | et al., M. Gloeckler |
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| 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. |
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| Venue | IEEE |
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| Source | Colorado State University |
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| Document Type | Conference Papers (Word document) |
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| Resource Date | 2004 |
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|
| Post Date | 02/07/2005 |
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| Title | TECHNOLOGY AND MARKET CHALLENGES TO MAINSTREAM THIN-FILM PHOTOVOLTAIC MODULES AND APPLICATIONS |
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| Link | (PDF 276 KB) Download Acrobat Reader. |
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| 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. |
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| Venue | |
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| Source | N/A |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 2004 |
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|
| Post Date | 02/09/2005 |
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| Title | CONTINUOUS, IN-LINE PROCESSING OF CDS/CDTE DEVICES: PROGRESS TOWARDS CONSISTENT STABILITY |
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| Link | (PDF 98 KB) Download Acrobat Reader. |
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| Authors | K. L. Barth, R. A. Enzenroth, W. S. Sampath |
|---|
| Description | Two results pertaining to CdTe device stability are presented here: 1) The process conditions, particularly the CdCl 2 treatment, have a significant effect on device stability and 2) a saturation in the loss of efficiency over time in accelerated indoor stress has been observed for a large number of devices. CdTe, degradation, fabrication... |
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| Venue | EuroPV |
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| Source | Colorado State University |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 2004 |
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|
| Post Date | 02/08/2005 |
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| Title | COPPER INCLUSION AND MIGRATION FROM THE BACK CONTACT IN CDTE SOLAR CELLS |
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| Link | (MS Word 791 KB) |
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| Authors | C. R. Corwine, et al. |
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| Description | Metallic back contacts to CdS/CdTe solar cells will in general form Schottky barriers. Better performance is achieved with the inclusion of Cu in the back contact. This study uses current-voltage, capacitance-voltage, and laser beam induced current measurements to analyze as-deposited CdS/CdTe solar cells prepared with varying back contact Cu amounts and to evaluate changes in cell performance following elevated-temperature stress. A simple model is proposed to explain both the observed differences in device behavior as copper is added or removed from the contact region, and how copper movement depends on electrical bias. |
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| Venue | Draft |
|---|
| Source | Colorado State University |
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| Document Type | Conference Papers (Word document) |
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| Resource Date | 2004 |
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|
| Post Date | 02/09/2005 |
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| Title | CU K-EDGE X-RAY FINE STRUCTURE CHANGES IN CDTE WITH CDCL2 PROCESSING |
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| Link | (PDF 86 KB) Download Acrobat Reader. |
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| Authors | A. Compaan, et al., X. Liu |
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| Description | MR-CAT beamline of the Advanced Photon Source at Argonne National Laboratory to study the fine structure in the Cu K-edge x-ray absorption in 3 mm thick polycrystalline films of CdTe on fused silica. 4 nm of evaporated Cu is diffused either with or without prior vapor CdCl2 treatments in dry air. Cu absorption is monitored through the Cu K a fluorescence using a 13 element Ge detector. The radial distribution junction inferred from the absorption fine structure indicates predominantly Cu2Te when Cu is diffused into the as deposited CdTe film but indicates a CuxO environment when Cu is diffused after the vapor CdCl2 treatment. |
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| Venue | European MRS |
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| Source | University of Toledo |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 2004 |
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| Post Date | 02/14/2005 |
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| Title | CIGS J-V DISTORTION IN THE ABSENCE OF BLUE PHOTONS |
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| Link | (MS Word 158 KB) |
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| Authors | et al., A. O. Pudov |
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| 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. |
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| Venue | EMRS |
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| Source | Colorado State University |
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| Document Type | Conference Papers (Word document) |
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| Resource Date | 2004 |
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| Post Date | 02/08/2005 |
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| Title | CDTE BACK CONTACT: RESPONSE TO COPPER ADDITION AND OUT-DIFFUSION |
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| Link | (PDF 345 KB) Download Acrobat Reader. |
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| Authors | et al., C. Jenkins |
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| Description | The back-contact barrier of CdTe solar cells plays an important role in cell operation, and it is substantially altered by both the amount of copper used in forming the contact and the movement of copper away from the contact during elevated temperature stress. It is shown that a simple model can explain the differences in current-voltage curves, cell uniformity, and capacitance as copper is added or moved out of the contact region, as well as the dependence of copper movement on electrical bias. |
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| Venue | draft |
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| Source | Colorado State University |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 2004 |
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| Post Date | 02/07/2005 |
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| Title | POLYCRYSTALLINE THIN-FILM PHOTOVOLTAIC TECHNOLOGIES: PROGRESS AND TECHNICAL ISSUES |
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| Link | (PDF 370 KB) Download Acrobat Reader. |
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| Author | H. S. Ullal |
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| 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. |
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| Venue | PVSEC 19 |
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| Source | National Renewable Energy Laboratory |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 2004 |
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| Post Date | 02/08/2005 |
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| Title | CONTINUOUS, IN-LINE PROCESSING OF CDS/CDTE DEVICES: PROGRESS TOWARDS CONSISTENT STABILITY |
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| Link | (PDF 98 KB) Download Acrobat Reader. |
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| Authors | K. L. Barth, R. A. Enzenroth, W. S. Sampath |
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| Description | A technology for continuous in-line processing of thin film CdS/CdTe devices has been developed in our laboratory. A CdTe PV device fabrication system has been operating for approximately 6 years and a full prototype manufacturing system for 16.5 x 16.5 inch substrates is under construction. Utilizing this technology, it has been demonstrated that at optimum process conditions good device stability (resistance to performance degradation) can be obtained. Two results pertaining to CdTe device stability are presented here: 1) The process conditions, particularly the CdCl2 treatment... |
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| Venue | EuroPV |
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| Source | Colorado State University |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 2004 |
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| Post Date | 02/09/2005 |
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| Title | CU K-EDGE XAFS IN CDTE BEFORE AND AFTER TREATMENT WITH CDCL2 |
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| Link | (PDF 204 KB) Download Acrobat Reader. |
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| Authors | et al., X. Liu |
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| Description | We have used the fine structure in the Cu K-edge x-ray absorption spectrum to help elucidate the lattice location of Cu in polycrystalline, thin-film CdTe solar cells. In particular, we have studied how the typical CdCl2 vapor treatment in dry air changes the local environment of the Cu in CdTe. We find the Cu absorption spectrum to be similar to that of Cu2Te in the asdeposited CdTe film but to convert to a spectrum similar to Cu2O environment after the vapor CdCl2 treatment. |
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| Venue | Materials Research Society Symposium Proceedings spring 2003, Symposium B "Compound Semiconductor Photovoltaics," paper B3.5 |
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| Source | University of Toledo |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 06/01/2003 |
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| Post Date | 02/09/2005 |
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| Title | THE MESOSCALE PHYSICS OF LARGE-AREA PHOTOVOLTAICS |
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| Link | (PDF 252 KB) Download Acrobat Reader. |
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| Authors | et al., V. G. Karpov |
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| 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. |
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| Venue | 29th IEEE Osaka |
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| Source | University of Toledo |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 05/16/2003 |
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| Post Date | 02/07/2005 |
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| Title | PROGRESS IN U.S. PHOTOVOLTAICS: LOOKING BACK 30 YEARS AND LOOKING AHEAD 20 |
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| Link | (PDF 310 KB) Download Acrobat Reader. |
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| Author | T. Surek |
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| Description | Technology and learning curve analysis of R&D. |
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| Venue | Osaka IEEE |
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| Source | National Renewable Energy Laboratory |
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| Document Type | Conference Papers (Adobe Postscript file) |
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| Resource Date | 2003 |
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