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Advanced processing of CdTe- and CuIn{sub x}Ga{sub 1{minus}x}Se{sub 2}-based solar cells. Phase 1 annual subcontract report, 18 April 1995--17 April 1996

Description: The main objective of this project to develop high-efficiency CdTe solar cells based on processing conditions favorable for manufacturing processes. This report presents the results on work performed during the first phase of this project. One of the major issues addressed is the use of soda-lime glass substrates in place of the borosilicate glass often used for laboratory devices; another task is the preparation of Cu(In, Ga) Se{sub 2} solar cells by selenizing suitable precursor films. Emphasis is placed on processing and how different reaction schemes affect device performance. It was found that different reaction schemes not only change the bulk properties of Cu(In, Ga) Se{sub 2}, but also its surface properties, which critically affect device performance. Although the objective is to optimize processing to meet the manufacturing constraints, work has not been limited within these requirements.
Date: March 1, 1997
Creator: Morel, D.L. & Ferekides, C.S.
Partner: UNT Libraries Government Documents Department

Polycrystalline thin film cadmium telluride solar cells fabricated by electrodeposition. Annual technical report, 20 March 1995--19 March 1996

Description: The objective of this project is to develop improved processes for fabricating CdTe/CdS polycrystalline thin-film solar cells. Researchers used electrodeposition to form CdTe; electrodeposition is a non-vacuum, low-cost technique that is attractive for economic, large-scale production. During the past year, research and development efforts focused on several steps that are most critical to the fabricating high-efficiency CdTe solar cells. These include the optimization of the CdTe electrodeposition process, the effect of pretreatment of CdS substrates, the post-deposition annealing of CdTe, and back-contact formation using Cu-doped ZnTe. Systematic investigations of these processing steps have led to a better understanding and improved performance of the CdTe-based cells. Researchers studied the structural properties of chemical-bath-deposited CdS thin films and their growth mechanisms by investigating CdS samples prepared at different deposition times; investigated the effect of CdCl{sub 2} treatment of CdS films on the photovoltaic performance of CdTe solar cells; studied Cu-doped ZnTe as a promising material for forming stable, low-resistance contacts to the p-type CdTe; and investigated the effect of CdTe and CdS thickness on the photovoltaic performance of the resulting cells. As a result of their systematic investigation and optimization of the processing conditions, researchers improved the efficiency of CdTe/CdS cells using ZnTe back-contact and electrodeposited CdTe. The best CdTe/CdS cell exhibited a V{sub oc} of 0.778 V, a J{sub sc} of 22.4 mA/cm{sup 2}, a FF of 74%, and an efficiency of 12.9% (verified at NREL). In terms of individual parameters, researchers obtained a V{sub oc} over 0.8 V and a FF of 76% on other cells.
Date: April 1, 1997
Creator: Trefny, J.U. & Mao, D.
Partner: UNT Libraries Government Documents Department

Module process optimization and device efficiency improvement for stable, low-cost, large-area, cadmium telluride-based photovoltaic module production. Final subcontract report, 1 July 1990--30 April 1994

Description: This report describes work performed under a three-phase subcontract. The objectives of the program include (1) achievement of active-area efficiencies of greater than 14% on small cells; (2) achievement of aperture-area efficiencies of greater than 13% on 0.09-m{sup 2} (1 ft{sup 2}) modules; (3) achievement of aperture-area efficiencies of greater than 12.5% on 0.37-m{sup 2} (4 ft{sup 2}) modules; and achievement of greater than 20-year module life (based on life testing extrapolations) with no greater than 10% efficiency degradation. The results obtained and described herein include the following: (1) efficiencies of 12.7% were achieved on small-area devices; (2) 0.09-m{sup 2} (1 ft{sup 2}) modules achieved greater than 8% aperture-area efficiency, but work for further efficiency improvement was redirected toward the 0.37-M{sup 2} (4 if) modules; (3) 0.37-m{sup 2} (4 ft{sup 2}) modules achieved 26.5-W output, which calculates to 8.0% aperture-area efficiency; (4) consistent prototype production was focused on and substantially achieved within Phase 2; (5) life testing at the National Renewable Energy Laboratory showed no inherent stability problems with the CdTe technology, and the accuracy of module measurement was satisfactorily resolved; and (6) a ``cradle-to-cradle`` recycling program was begun based upon the philosophy that the establishment of such mechanisms will be required to ensure maximum recapture and recycling of all manufacturing waste materials and/or modules returned from the field.
Date: June 1, 1994
Creator: Albright, S. P. & Johnson, S. X.
Partner: UNT Libraries Government Documents Department

Technology support for initiation of high-throughput processing of thin-film CdTe PV modules. Phase 3 final technical report, 14 March 1997--1 April 1998

Description: Thin-film PV devices based on cadmium telluride have been identified as one of the candidates for high-performance, low-cost source of renewable electrical energy. Roadblocks to their becoming a part of the booming PV market growth have been a low rate of production and high manufacturing cost caused by several rate-limiting process steps. Solar Cells Inc. has focused on the development of manufacturing processes that will lead to high volume and low-cost manufacturing of solar cells and on increasing the performance of the present product. The process research in Phase 3 was concentrated on further refinement of a newly developed vapor transport deposition (VTD) process and its implementation into the manufacturing line. This development included subsystems for glass substrate transport, continuous feed of source materials, generation of source vapors, and uniform deposition of the semiconductor layers. As a result of this R and D effort, the VTD process has now achieved a status in which linear coating speeds in excess of 8 ft/min have been achieved for the semiconductor, equal to about two modules per minute, or 144 kW per 24 hour day. The process has been implemented in a production line, which is capable of round-the-clock continuous production of coated substrates 120 cm x 60 cm in size at a rate of 1 module every four minutes, equal to 18 kW/day. Currently the system cycle time is limited by the rate of glass introduction into the system and glass heating, but not by the rate of the semiconductor deposition. A new SCI record efficiency of 14.1% has been achieved for the cells.
Date: September 1, 1998
Creator: Powell, R.C.; Dorer, G.L.; Jayamaha, U. & Hanak, J.J.
Partner: UNT Libraries Government Documents Department

Technology support for initiation of high-throughput processing of thin-film CdTe PV modules. Phase II technical report, March 14, 1996--March 13, 1997

Description: Research at Solar Cells Inc. is focused on developing processes which will lead to high volume and low cost manufacturing of solar cells and to increase the performance of their present technology. The process research has focused on developing vapor transport deposition of the semiconductors, eliminating wet chemistry steps while minimizing the chloride treatment time, forming a low-loss back contact using only dry processing, and an improved interconnection technique. The performance improvement work has focused on the increase of the photocurrent by a combination of more transparent glass substrates and a thinner CdS window layer deposited on an i-SnO{sub 2} buffer layer. SCI record 13.0% 1 cm{sup 2} devices have been fabricated using these techniques. Stability monitoring continues and shows minimal degradation for over 20,000 hours of continuous light soak at 0.8 sun illumination.
Date: September 1, 1997
Creator: Sasala, R.; Powell, R. & Dorer, G.
Partner: UNT Libraries Government Documents Department

Fabrication of stable, large-area thin-film CdTe photovoltaic modules. Final subcontract report, May 10, 1991--February 28, 1995

Description: During the period of this subcontract, May 1991 through February 1995, Solar Cells, Inc. has developed and demonstrated a low-cost process to fabricate stable large-area cadmium telluride based thin-film photovoltaic modules. This report summarizes the final phase of the project which is concentrated on process optimization and product life tests. One of the major post-deposition process steps, the CdCl{sub 2} heat treatment, has been experimentally replaced with alternative treatments with vapor chloride or chlorine gas. Material and device qualities associated with alternative treatments are comparable or superior to those with the conventional treatment. Extensive experiments have been conducted to optimize the back-electrode structure in order to ensure long term device stability. Numerous small-area cells and minimodules have been subjected to a variety of stress tests, including but not limited to continuous light soak under open or short circuit or with resistive load, for over 10,000 hours. Satisfactory stability has been demonstrated on 48 cm{sup 2} and 64 cm{sup 2} minimodules under accelerated tests and on 7200 cm{sup 2} large modules under normal operating conditions. The conversion efficiency has also been significantly improved during this period. The total area efficiency of 7200 cm{sup 2} module has reached 8.4%, corresponding to a 60.3W normalized output; the efficiency of 64 cm{sup 2} minimodules and 1.1 cm{sup 2} cells has reached 10.5% (aperture area) and 12.4% (total area), respectively.
Date: June 1, 1995
Creator: Zhou, T.X.
Partner: UNT Libraries Government Documents Department

Polycrystalline Thin-Film Cadmium Telluride Solar Cells Fabricated by Electrodeposition; Final Technical Report, 20 March 1995-15 June 1998

Description: This report summarizes work performed by the Colorado School of Mines Department of Physics under this subcontract. Based on the studies conducted, researchers increased the efficiency of the cells with electrodeposited CdTe and CBD CdS by 3% on average ({approx}30 relative %). The improvement came from 1. Optimization of CdS initial thickness taking into account CdS consumption of CdTe during the CdTe/CdS post-deposition treatment; optimization of CdS post-deposition treatment with CdCl2 aimed at prevention of Te diffusion into CdS and improvement of the CdS film morphology and electronic properties. That led to a considerable increase in short circuit current, by 13% on average. 2. Optimization of CdTe thickness and post-deposition treatment which led to a significant increase in Voc, by {approx}70 mV. The highest Voc obtained exceeded 800 mV. 3. Development of a ZnTe:Cu/Metal back contact processing procedure that included selection of optimal Cu content, deposition regime and post-deposition treatment conditions. As a result, back contact resistance as low as 0.1W-cm2 was obtained. The cell stability was measured on exposure to accelerated stress conditions. Preliminary studies of some new approaches to improvement of CdS/CdTe structure were conducted.
Date: January 27, 1999
Creator: Trefny, J. U.; Mao, D.; Kaydanov, V.; Ohno, T. R.; Williamson, D. L.; Collins, R. et al.
Partner: UNT Libraries Government Documents Department

Technical evaluation of Solar Cells, Inc., CdTe modules and array at NREL

Description: The Engineering and Technology Validation Team at the National Renewable Energy Laboratory (NREL) conducts in-situ technical evaluations of polycrystalline thin-film photovoltaic (PV) modules and arrays. This paper focuses on the technical evaluation of Solar Cells, Inc., (SCI) cadmium telluride (CdTe) module and array performance by attempting to correlate individual module and array performance. This is done by examining the performance and stability of the modules and array over a period of more than one year. Temperature coefficients for module and array parameters (P{sub max}V{sub oc}, V{sub max}, I{sub sc}, I{sub max}) are also calculated.
Date: May 1, 1996
Creator: Kroposki, B.; Strand, T. & Hansen, R.
Partner: UNT Libraries Government Documents Department

High-throughput manufacturing of thin-film CdS/CdTe photovoltaic modules. Annual subcontract report, 16 November 1994--15 November 1995

Description: The objectives of this subcontract are to advance Solar Cells, Inc.`s (SCI`s) photovoltaic manufacturing technologies, reduce module production costs, increase module performance, and provide the groundwork for SCI to expand its commercial production capacities. Activities during the second year of the program concentrated on process development, equipment design and testing, quality assurance, and ES and H programs. These efforts broadly addressed the issues of the manufacturing process for producing thin-film monolithic CdS/CdTe photovoltaic modules.
Date: February 1, 1997
Creator: Sandwisch, D.W.
Partner: UNT Libraries Government Documents Department

Device physics of thin-film polycrystalline cells and modules. Annual subcontract report, 6 December 1995--5 December 1996

Description: During 1996, a number of projects were carried out at Colorado State University (CSU) on Cu(In, Ga)Se{sub 2} (CIGS) and CdTe solar cells and small modules. CSU participated directly in the deposition of CIGS at NREL for the first time. Five separate substrates were used, and sodium was both deliberately introduced and deliberately blocked from exiting soda-lime substrates. In general, sodium in the CIGS led to better junction properties and higher efficiency. In other CIGS measurements, CSU showed that electrodeposited absorber material made at NREL produced competitive cells. Voltages, normalized to bandgap, were about 50 mV less than the best evaporated CIGS cells. CSU also showed, in collaboration with Solarex, that the existence of a high-resistivity ZnO layer is probably not critical for cells with relatively thick CdS window layers. In collaboration with seven CdTe fabrication laboratories, CSU measured the effect of CdS thickness on cell parameters. Although voltage and fill-factor generally degrade for CdS thickness below 100 nm, the exceptions suggest that with at least some fabrication techniques, CdS thickness can be reduced to the point that high quantum efficiency in the blue and a good diode junction are not mutually exclusive. A number of artifacts were investigated that appear in module measurement and analysis, but that are generally negligible for small test cells. These include effects due to module-cell geometry and misleading conclusions from selective illumination experiments. NREL data from the highest-efficiency CIGS and CdTe cells were analyzed to provide direct comparisons of different fabrication techniques. The three commonly used NREL deposition systems have produced CIGS cells with very similar junction properties. 20 figs.
Date: October 1, 1997
Creator: Sites, J.R.
Partner: UNT Libraries Government Documents Department

Electrical Characterization of Etched Grain-Boundary Properties from As-Processed px-CdTe Based Solar Cells

Description: An ability to lift off or separate the thin-film polycrystalline CdTe from the CdS, without the use of chemical etches, has enabled direct electrical characterization of the as-processed CdTe near the CdTe/CdS heterointerface. We use this ability to understand how a back-contact, nitric-phosphoric (NP) etch affects the grain boundaries throughout the film. Quantitative determination of the grain-boundary barrier potentials and estimates of doping density near the grain perimeter are determined from theoretical fits to measurements of the current vs. temperature. Estimates of the bulk doping are determined from high-frequency resistivity measurements. Also, a variable doping density within the grains of non-etched material has been determined. These results allow a semi-quantitative grain-boundary band diagram to be drawn that should aid in determining more-accurate two-dimensional models for polycrystalline CdTe solar cells.
Date: October 22, 1998
Creator: Woods, L. M.; Robinson, G. Y. (Colorado State University, Ft. Collins, CO) & Levi, D. H. (National Renewable Energy Laboratory) Kaydanov, V. (Colorado School of Mines, Golden, CO)
Partner: UNT Libraries Government Documents Department

Development of a computer model for polycrystalline thin-film CuInSe{sub 2} and CdTe solar cells; Annual subcontract report, 1 March 1992--28 February 1993

Description: Solar cells operate by converting the radiation power from sun light into electrical power through photon absorption by semiconductor materials. The elemental and compound material systems widely used in photovoltaic applications can be produced in a variety of crystalline and non-crystalline forms. Although the crystalline group of materials have exhibited high conversion efficiencies, their production cost are substantially high. Several candidates in the poly- and micro-crystalline family of materials have recently gained much attention due to their potential for low cost manufacturability, stability, reliability and good performance. Among those materials, CuInSe{sub 2} and CdTe are considered to be the best choices for production of thin film solar cells because of the good optical properties and almost ideal band gap energies. Considerable progress was made with respect to cell performance and low cost manufacturing processes. Recently conversion efficiencies of 14.1 and 14.6% have been reported for CuInSe{sub 2} and CdTe based solar cells respectively. Even though the efficiencies of these cells continue to improve, they are not fully understood materials and there lies an uncertainty in their electrical properties and possible attainable performances. The best way to understand the details of current transport mechanisms and recombinations is to model the solar cells numerically. By numerical modeling, the processes which limit the cell performance can be sought and therefore, the most desirable designs for solar cells utilizing these materials as absorbers can be predicted. The problems with numerically modeling CuInSe{sub 2} and CdTe solar cells are that reported values of the pertinent material parameters vary over a wide range, and some quantities such as carrier concentration are not explicitly controlled.
Date: March 1, 1994
Creator: Gray, J.L.; Schwartz, R.J. & Lee, Y.J.
Partner: UNT Libraries Government Documents Department

High-efficiency, thin-film cadmium telluride photovoltaic cells. Annual subcontract report, 20 January 1994--19 January 1995

Description: This report describes work performed to develop and optimize the process of radio frequency (RF) sputtering for the fabrication of thin-film solar cells on glass. The emphasis is on CdTe-related materials including CdTe, CdS, ZnTe, and ternary alloy semiconductors. Pulsed laser physical vapor deposition (LPVD) was used for exploratory work on these materials, especially where alloying or doping are involved, and for the deposition of cadmium chloride layers. For the sputtering work, a two-gun sputtering chamber was implemented, with optical access for monitoring temperature and growth rate. We studied the optical and electrical properties of the plasmas produced by two different kinds of planar magnetron sputter guns with different magnetic field configurations and strengths. Using LPVD, we studied alloy semiconductors such as CdZnTe and heavily doped semiconductors such as ZnTe:Cu for possible incorporation into graded band gap CdTe-based photovoltaic devices.
Date: August 1, 1995
Creator: Compaan, A.D.; Bohn, R.G. & Rajakarunanayake, Y.
Partner: UNT Libraries Government Documents Department

Cadmium telluride photovoltaic manufacturing technology. Annual subcontract report, 7 January 1994--6 January 1995

Description: This report describes work performed by Golden Photon, Inc. (GPI), to conduct research under the PVMaT program, Phase 2B. The objective of the research is to advance GPI`s manufacturing technology, reduce module production costs, increase average module performance, and identify ways to expand production capacity. More specifically, the tasks established for Phase I were to design and install leasehold improvements for the 2-MW production line; to improve and develop product design, efficiency, and marketability; to ensure uninterrupted qualified supplies and raw materials for production; to address environmental, health, and safety issues encountered during production of photovoltaic modules; and to reduce the cost of manufacturing modules. During the first half of this reporting period, the development, design, and debugging of cell interconnection equipment critical to start-up was completed. During the second and third quarters, the primary focus was on the substrate deposition steps (tin oxide, cadmium sulfide, and cadmium telluride) and cell interconnection steps (division). In general, process development, engineering, and quality teams continued to focus on identifying, baselining, and improving (through redesign) actual process equipment operation parameters to meet the required PV panel specifications and improve process throughput rates and yields.
Date: November 1, 1995
Creator: Weisiger, D.; Albright, S.P.; Brines, J. & Thompson, R.
Partner: UNT Libraries Government Documents Department

Health and environmental hazards of CdTe photovoltaic module production, use and decommissioning

Description: Health and environmental (H&E) risks presented by CdTe photovoltaic module production, use and decommissioning have been reviewed and discussed by several authors. Several H&E concerns exit. The estimated risks are based on extrapolations of toxicity, environmental mobility, and bioavailability data for other inorganic cadmium compounds. Little information, however, is available about CdTe itself. In response to the increased interest in CdTe, Brookhaven National Laboratory (BNL) has been engaged in a cooperative research program with the National Institute of Environmental Health Sciences (NIEHS), the Fraunhofer Institute for Solid State Technology (IFT), and the GSF Institute of Chemical Ecology to develop fundamental toxicological and environmental data for CdTe. This paper describes the results of these studies, and their potential implications with respect to the H&E hazards presented by CdTe module production, use and decommissioning.
Date: February 1, 1995
Creator: Moskowitz, P. D.; Steinberger, H. & Thumm, W.
Partner: UNT Libraries Government Documents Department

Preparation and properties of evaporated CdTe films: Final subcontract report, 16 February 1985-31 March 1987

Description: Previous work on evaporated CdTe films for photovoltaics showed no clear path to successful p-type doping of CdTe during deposition. Post-deposition annealing of the films in various ambients thus was examined as a means of doping. Anneals were done in Te, Cd, P, and As vapors and in vacuum, air and Ar, all of which showed large effects on series resistance and diode parameters. With As, series resistance values of In/p-CdTe/graphite structures decreased markedly. This decrease was due to a decrease in grain boundary and/or back contact barrier height, and thus was due to large increases in mobility; the carrier density was not altered substantially. Although the series-resistance decreases were substantial, the diode characteristics became worse. The decreases were not observed when CdS/CdTe cells were fabricated on Te vapor-annealed films. Preparation of ZnO films by reactive evaporation yielded promising results. Deposition of p-ZnTe films by hot-wall vapor evaporation, using conventional techniques, yielded acceptable films without intentional doping.
Date: July 1, 1987
Creator: Bube, R H; Fahrenbruch, A L & Chien, K F
Partner: UNT Libraries Government Documents Department

Preparation and properties of evaporated CdTe films compared with single crystal CdTe. Annual report, 1 February 1983-31 January 1984

Description: Variation of CdS/CdTe/graphite thick film solar cell properties was investigated as a function of temperature for CdS film deposition. A maximum open-circuit voltage of 0.67 V was found for a deposition temperature of 160/sup 0/C, corresponding to a CdS film resistivity of 150 ohm-cm. The effect is not due to avoidance of higher temperature annealing of the CdTe film in higher temperature CdS film depositions nor to the diffusion of In from the outermost CdS: In layer. The effect of coating the graphite before CdTe deposition with Au or Cu was also investigated. Although high concentrations of both Au or Cu could be determined after CdTe deposition, CdTe films grown on this coated graphite had lower hole densities than films grown on uncoated graphite. Photovoltaic parameters of thin-film CdS/CdTe/graphite solar cells were investigated as a function of storage time to check the stability of these cells. Initial degradation of parameters (especially fill factor) could be reversed by heat treatment in hydrogen, with subsequent properties being stable. Heat treatment of CdS/CdTe/graphite solar cells in air increases cell resistivity and decreases fill factor; heat treatment in hydrogen produces the reverse effect. The hole density is not affected by these heat treatments, suggesting that effects are associated with grain boundaries in the film.
Date: September 1, 1984
Creator: Bube, R; Fahrenbruch, A; Huber, W; Fortmann, C & Thorpe, T
Partner: UNT Libraries Government Documents Department

Annual Report: Photovoltaic Subcontract Program FY 1990

Description: This report summarizes the progress of the Photovoltaic (PV) Subcontract Program of the Solar Energy Research Institute (SERI) from October 1, 1989 through September 30, 1990. The PV Subcontract Program is responsible for managing the subcontracted portion of SERI's PV Advanced Research and Development Project. In fiscal year 1990, this included more than 54 subcontracts with a total annualized funding of approximately $11.9 million. Approximately two-thirds of the subcontracts were with universities at a total funding of nearly $3.3 million. The six technical sections of the report cover the main areas of the subcontract program: the Amorphous Silicon Research Project, Polycrystalline Thin Films, Crystalline Silicon Materials Research, High-Efficiency Concepts, the New Ideas Program, and the University Participation Program. Technical summaries of each of the subcontracted programs provide a discussion of approaches, major accomplishments in FY 1990, and future research directions. Another section introduces the PVMaT project and reports on its progress.
Date: March 1, 1991
Creator: Summers, K. A.
Partner: UNT Libraries Government Documents Department

Development of high-efficiency, thin-film CdTe solar cells. Final subcontract report, 1 February 1992--30 November 1995

Description: This report describes work performed by the Georgia Institute of Technology (GIT) to bring the polycrystalline CdTe cell efficiency a step closer to the practically achievable efficiency of 18% through fundamental understanding of detects and loss mechanisms, the role of chemical and heat treatments, and investigation of now process techniques. The objective was addressed by a combination of in-depth characterization, modeling, materials growth, device fabrication, and `transport analyses of Au/Cu/CdTe/CdS/SnO {sub 2} glass front-wall heterojunction solar cells. GiT attempted to understand the loss mechanism(s) in each layer and interface by a step-by-step investigation of this multilayer cell structure. The first step was to understand, quantify, and reduce the reflectance and photocurrent loss in polycrystalline CdTe solar calls. The second step involved the investigation of detects and loss mechanisms associated with the CdTe layer and the CdTe/CdS interface. The third stop was to investigate the effect of chemical and heat treatments on CdTe films and cells. The fourth step was to achieve a better and reliable contact to CdTe solar cells by improving the fundamental understanding. Of the effects of Cu on cell efficiency. Finally, the research involved the investigation of the effect of crystallinity and grain boundaries on Cu incorporation in the CdTe films, including the fabrication of CdTe solar calls with larger CdTe grain size.
Date: January 1, 1996
Creator: Rohatgi, A.; Chou, H.C.; Kamra, S. & Bhat, A.
Partner: UNT Libraries Government Documents Department

Device physics of thin-film polycrystalline cells and modules. Annual subcontract report, December 6, 1993--December 5, 1994

Description: Progress has been made in several applications of device physics to thin-film polycrystalline cells and modules. At the cell level, results include a more quantitative separation of photon losses, the impact of second barriers on cell operation, and preliminary studies of how current-voltage curves are affected by band offsets. Module analysis includes the effects of the typical monolithic, series-connected cell geometry, analytical techniques when only the two module leads are accessible, and the impact of chopping frequency, local defects, and high-intensity beams on laser-scanning measurements.
Date: May 1, 1995
Creator: Sites, J.R.
Partner: UNT Libraries Government Documents Department

Baseline Evaluation of Thin-Film Amorphous Silicon, Copper Indium Diselenide, and Cadmium Telluride for the 21st Century: Preprint

Description: This paper examines three thin-film PV technologies: amorphous silicon, cadmium telluride, and copper indium selenide. The purpose is to: (1) assess their status and potential; (2) provide an improved set of criteria for comparing these existing thin films against any new PV technological alternatives, and examining the longer-term (c. 2050) potential of thin films to meet cost goals that would be competitive with conventional sources of energy without any added value from the substantial environmental advantages of PV. Among the conclusions are: (1) today's thin films have substantial economic potential, (2) any new approach to PV should be examined against the substantial achievements and potential of today's thin films, (3) the science and technology base of today's thin films needs substantial strengthening, (4) some need for alternative technologies exists, especially as the future PV marketplace expands beyond about 30 GW of annual production.
Date: April 1, 1999
Creator: Zweibel, K.
Partner: UNT Libraries Government Documents Department

Processing and modeling issues for thin-film solar cell devices. Final report

Description: During the third phase of the subcontract, IEC researchers have continued to provide the thin film PV community with greater depth of understanding and insight into a wide variety of issues including: the deposition and characterization of CuIn{sub 1-x}Ga{sub x}Se{sub 2}, a-Si, CdTe, CdS, and TCO thin films; the relationships between film and device properties; and the processing and analysis of thin film PV devices. This has been achieved through the systematic investigation of all aspects of film and device production and through the analysis and quantification of the reaction chemistries involved in thin film deposition. This methodology has led to controlled fabrications of 15% efficient CuIn{sub 1-x}Ga{sub x}Se{sub 2} solar cells over a wide range of Ga compositions, improved process control of the fabrication of 10% efficient a-Si solar cells, and reliable and generally applicable procedures for both contacting and doping films. Additional accomplishments are listed below.
Date: November 1, 1997
Creator: Birkmire, R.W. & Phillips, J.E.
Partner: UNT Libraries Government Documents Department