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Alternative window schemes for CuInSe{sub 2}-based solar cells. Annual report, 1 November 1995--31 October 1996

Description: The objectives of this program are to develop alternate heterojunction partner layers (buffer layers) for high efficiency CuInSe{sub 2}-based thin-film solar cells, and improve the understanding of how these layers and the details of processing affect cell performance. Investigations have primarily involved three tasks: (1) MOCVD growth of non-cadmium containing buffer layers; (2) optimized processing of buffer layers for high efficiency solar cells; and (3) electrical and physical characterization of layers and devices. Investigations of alternative buffer layers emphasized studies of ZnO grown by MOCVD. Using CIS substrates obtained form Siemens for process development, it was determined that growth procedures that resulted in good results with Siemens CIS (non-sulfur containing material) substrates also worked well with NREL CIGS material. A two step process was developed for growing highly resistive ZnO buffer layers (i-ZnO). In particular, after growing 100 to 150 {angstrom} of ZnO at 250 C, an additional 600 {angstrom} to 800 {angstrom} were grown at 100 C. Collaboration with NREL resulted in a n-ZnO/i-ZnO/CIGS cell which was determined to have a total area efficiency of 12.7%, and an active area efficiency greater than 13%. After growing i-ZnO with the two-step process onto NREL CIGS material, the i-ZnO/CIGS film structure was sent to NREL for deposition of a TCO, namely, conducting ZnO (n-ZnO). Collector grids and a MgF{sub 2} AR coating were also deposited at NREL. Low level efforts were devoted to studies of ZnSe and InSe buffer layers. A total area efficiency of 9.5% was achieved for a completed ZnSe/CIS cell making use of a RF sputtered ZnO for a TCO. Investigations of In{sub x}Se{sub y} (InSe) buffer layers were also initiated this past year.
Date: October 1, 1997
Creator: Olsen, L.C.
Partner: UNT Libraries Government Documents Department

CIS-based thin film PV technology. Phase 2 technical report, October 1996--October 1997

Description: This report describes work performed during Phase 2 of Siemens Solar Industries` (SSI) subcontract. Studies of the differences between reactors continued, resulting in adjustment of most of the process conditions to more closely mimic process conditions in the baseline reactor, thereby mitigating most of the process differences. SSI designed and built a new large-area reactor that is a more-direct scale-up of the baseline reactor. This reactor became operational during Phase 2 and was successfully demonstrated by initial circuit performance for 28-cm x 30-cm circuits averaging 10.6%, which compares favorably to the 10-cm x 10-cm baseline. SSI also defined a package for introductory products in support of the DOE long-term goal of systems that last at least 30 years. SSI also introduced two new CIS-based products: the product designations are ST5 and ST10, which are 21-cm x 33-cm/5-watt and 39-cm x 33-cm/10-watt modules designed for 12-V systems. NREL reports 9.6% aperture-area efficiency on the samples (11.2% circuit-plate aperture area), which is the highest efficiency of any commercial noncrystalline module. SSI also delivered a set of modules to NREL for a 1-kW array replacing an existing 1-kW array based on an older absorber formation technology. NREL reports stable performance and an unprecedented average efficiency of over 9%. A champion module was confirmed by NREL to produce 40.6 watts for a new world-record efficiency of 11.1% on 3,665 cm{sup 2}. This demonstrated efficiency exceeds the 1995 DOE efficiency goal for CIS prototype modules and exceeds the year 2000 efficiency goals for amorphous silicon and cadmium telluride technologies.
Date: May 1, 1998
Creator: Tarrant, D.E. & Gay, R.R.
Partner: UNT Libraries Government Documents Department

Research on polycrystalline thin-film submodules based on CuInSe{sub 2} materials. Final subcontract report, 11 November 1990--30 June 1995

Description: This report describes work performed in development of CIS-based photovoltaic (PV) products. The activity began with developing manufacturable deposition methods for all required thin-film layers and developing and understanding processes using those methods. It included demonstrating the potential for high conversion efficiency and followed with developing viable methods for module segment formation and interconnection. These process steps were integrated to fabricate monolithic CIS-based submodules. An important result of this program is the basis of understanding established in developing this material for PV applications, which is necessary to address issues of manufacturability and cost-which were recognized early in the program as being determined by successful solutions to issues of yield, reproducibility, and control as much as by material and energy costs, conversion efficiency, and process speed. Solarex identified at least one absorber formation process that is very robust to shunt formation from pinholes or point defects, tolerant of variation in processing temperature and elemental composition, and is capable of producing high conversion efficiency. This program also allowed development and scale-up of processes for the deposition of all other substrate, heterojunction buffer, and window layers and associated scribing/module formation operations to 1000-CM{sup 2} size. At the completion of this program, Solarex has in place most of the necessary elements to begin the transition to pilot operation of CIS manufacturing activities.
Date: January 1, 1996
Creator: Arya, R.; Fogleboch, J.; Kessler, J.; Russell, L.; Skibo, S. & Wiedeman, S.
Partner: UNT Libraries Government Documents Department

Environmental issues related to commercialization of CulnSe{sub 2}- based photovoltaics

Description: One of the most promising materials for low-cost thin film photovoltaic cells is copper indium selenide (CuInSe{sub 2} or CIS). As with any new material, successful commercialization of CIS photovoltaic (PV) technology will require attention to environmental issues related to the sources of raw materials, their usage, and the disposal and/or recycling of products at the end of their useful life. This paper focuses on three specific environmental issues related to CIS technology: (i) Economics of the use and re-use of materials; (ii) regulations on environmental disposal and waste handling, and (iii) logistics and economics of recycling and disposing of products by industries faced with comparable environmental issues.
Date: July 1, 1996
Creator: Eberspacher, C.; Fthenakis, V.M. & Moskowitz, P.D.
Partner: UNT Libraries Government Documents Department

Research on high-efficiency, large-area, CuInSe{sub 2}-based thin- film modules. Annual subcontract report, 1 May 1992--15 Aug 1993

Description: This report describes work to demonstrate 12.5% aperture efficient, large-area (3900-cm{sup 2}) encapsulated thin-film CuInSe{sub 2} (CIS) photovoltaic modules. Module design consists of 53 series-connected ZnO/CdS/CIS/Mo/glass cells fabricated on a 4141-cm{sup 2} (128.6 {times} 32.2 cm) glass substrate with a nominal aperture area of 3895 cm{sup 2} (127.3 {times} 30.6 cm). Four CIS modules were shipped to NREL under the terms of the subcontract. Phase 2 consisted of fabricating large-area (3900-cm{sup 2}) modules for high-performance module processing. The large-area parts proved to be cumbersome, and we decided to use smaller substrates (100 cm{sup 2}) to accelerate the progress in solving the types of technical challenges that were discovered in processing large-area parts, and then to apply these solutions to larger areas to meet the objectives of the investigation. Most critical issues determining module yield losses can be grouped into three major categories: (1) Uniformity and reproducibility of the absorber formation process dominates the fundamental performance of the material over a large area, (2) interaction of the substrate with the Mm requires appropriate selection criterial and preparation techniques for minimizing defects that lead to shunting and areas of poor photoresponse, and (3) performance losses near interconnects reduce module performance and can cause inadequate performance through module durability testing.
Date: January 1, 1994
Creator: Knapp, K. E. & Gay, R. R.
Partner: UNT Libraries Government Documents Department

CIS-based thin film PV technology. Phase 1 annual technical report, September 1995--September 1996

Description: The primary objective of this subcontract is to establish reliable high-throughput, high-yield thin film deposition processes in order to make CIS a viable option for the next generation of photovoltaics. The primary goals for the project are to deliver a champion prototype 13% efficient large area module and to deliver sets of modules in 1-kW arrays composed of steadily increasing efficiency, reaching 1 kW of 12% efficient large-area modules by the end of the third year, demonstrating performance as well as commercial viability. The focus of the deliverables on large sets of high-performance modules reflects Siemens Solar Industries` commitment to demonstrating a reliable low-cost product. This document reports on progress from September 1995 through September 1996.
Date: April 1, 1997
Creator: Tarrant, D.E. & Gay, R.R.
Partner: UNT Libraries Government Documents Department

Environmental and health aspects of copper-indium-diselenide thin-film photovoltaic modules

Description: Copper-indium-diselenide (CIS) is a semiconductor compound that can be used to produce thin-film photovoltaic modules. There is on-going research being conducted by various federal agencies and private industries to demonstrate the commercial viability of this material. Because this is a new technology, and because scant information about the health and environmental hazards associated with the use of this material is available, studies have been initiated to characterize the environmental mobility and environmental toxicology of this compound. The objective of these studies is to identify the environmental and health hazards associated with the production, use, and disposal of CIS thin-film photovoltaic modules. The program includes both experimental and theoretical components. Theoretical studies are being undertaken to estimate material flows through the environment for a range of production options as well as use and disposal scenarios. The experimental programs characterize the physical, chemical e.g. leachability and biological parameters e.g. EC{sub 50} in daphnia and algae, and feeding studies in rats.
Date: December 31, 1994
Creator: Steinberger, H.; Thumm, W.; Freitag, R.; Moskowitz, P.D. & Chapin, R.
Partner: UNT Libraries Government Documents Department

Polycrystalline thin-film module and system performance

Description: The Module and System Performance and Engineering Project at the National Renewable Energy Laboratory (NREL) conducts in-situ technical evaluations of photovoltaic (PV) modules and systems (arrays). These evaluations on module/array performance and stability are conducted at the NREL Photovoltaic Outdoor Test Facility (OTF) in Golden, CO. The modules and arrays are located at 39.7{degree}N latitude, 105.2{degree}W longitude, and at 1,782 meters elevation. Currently, two polycrystalline thin-film technologies are the focus of the research presented here. The module structures are copper indium diselenide (CIS) from Siemens Solar Industries and cadmium telluride (CdTe) from Solar Cells, Inc. The research team is attempting to correlate individual module performance with array performance for these two polycrystalline thin-film technologies. This is done by looking at module and array performance over time. Also, temperature coefficients are determined at both the module and array level. Results are discussed.
Date: November 1, 1995
Creator: Strand, T.; Kroposki, B.; Hansen, R. & Mrig, L.
Partner: UNT Libraries Government Documents Department

Research on high-efficiency, large-area CuInSe{sub 2}-based thin-film modules. Final subcontract report, 16 August 1993--30 June 1995

Description: This final subcontract report, describing work to fabricate a large-area, stable, 12.5% (aperture)-efficient encapsulated CuInSe{sub 2} (CIS) module by scalable, low-cost techniques on inexpensive substrates. Demonstrated encapsulated module efficiencies (encapsulated 12.8%-efficient mini-module on 68.9cm{sup 2} and an NREL-verified 12.7%-efficient unencapsulated circuit on 69 CM{sup 2} with a prismatic cover) are the highest reported mini-module demonstrated (and verified by NREL). This is the first thin-film module of its size to exceed the 10% efficiency level. SSI also supplied NREL with a 1-kW array of large-area ({approximately}3890 CM{sup 2}) approximately 30-W modules. The NREL-verified performance of this array is a significant step toward meeting the efficiency target of the USDOE Five-Year Plan goals of 8%--10%-efficient commercial thin-film, flat-plate modules. Long-term outdoor stability of CIS and CIS-based absorbers was demonstrated by testing at NREL. Excellent stability was demonstrated for 6 years of outdoor exposure. The stability of the 1-kW Siemens CIS array, installed and tested at NREL, was also demonstrated for an exposure of about 1 year. The foundations have been laid to meet the thin-film milestones of the DOE Five-Year Plan. Outdoor testing has demonstrated excellent intrinsic module stability. Future plans include scaling these results to larger areas and emphasizing the reduction of variation methodology to lay the foundation for demonstrating the potential of CIS as a future commercial product.
Date: July 1, 1995
Creator: Tarrant, D.E. & Gay, R.R.
Partner: UNT Libraries Government Documents Department

Research on high efficiency, large-area CuInSe{sub 2}-based thin-film modules. Annual subcontract report, 1 May 1991--30 April 1992

Description: Objective was to demonstrate 12.5% aperture efficient, large area (3900 cm{sup 2}) encapsulated thin thin CuInSe{sub 2} (CIS) modules. The module design consists of 53 series-connected ZnO/CdS/CIS/Mo/glass cells fabricated on a glass substrate. A baseline characterization of the CIS modules was established during Phase 1. Maps of open circuit voltage provide information on junction quality uniformity. Maps of cell voltages at fixed forward bias show variations in resistance losses due to interconnects. Individual cell I-V curves can be evaluated. Physical nature of defects is correlated using OBIC, EBIC, SEM, tape adhesion, etc. A new world record of 37.7 W and 9.7% aperture efficiency was attained for an encapsulated module; an unencapsulated CIS module plate achieved 40.8 W and 10.5% aperture efficiency.
Date: February 1, 1993
Creator: Mitchell, K. W. & Eberspacher, C.
Partner: UNT Libraries Government Documents Department

ZnMgO by APCVD Enabling High-Performance Mid-bandgap CIGS on Polyimide Modules: October 2009--October 2010

Description: This Pre-Incubator project was designed to increase the 'real world' CIGS based photovoltaic module performance and decrease the Levelized Cost of Energy (LCOE) of systems utilizing those modules compared to our traditional CIGS based photovoltaic modules. This was enabled by a) increasing the CIGS bandgap and b) developing better matched device finishing layers to the mid-bandgap CIGS based photovoltaics; including window and buffer layers (and eventually the TCO). Incremental progress in the novel device performance was demonstrated throughout the program, and ultimately achieved performance results that exceeded the milestones ahead of schedule. Metal-oxide buffer layer devices with mid-bandgap CIGS alloys on polyimide substrates were produced with efficiencies of over 12%. Corresponding mid-bandgap devices with CdS buffers produced over 13% efficient devices. Furthermore, no obvious degradation in the device performance has been observed to date, after proper storage ambient of the different types of unencapsulated devices were identified.
Date: April 1, 2011
Creator: Woods, L.
Partner: UNT Libraries Government Documents Department

Understanding and managing health and environmental risks of CIS, CGS, and CdTe photovoltaic module production and use: A workshop

Description: Environmental, health and safety (EH&S) risks presented by CIS, CGS and CdTe photovoltaic module production, use and decommissioning have been reviewed and discussed by several authors. Several EH&S concerns exit. The estimated EH&S risks are based on extrapolations of toxicity, environmental mobility, and bioavailability data for other related inorganic compounds. Sparse data, however, are available for CIS, CGS or CdTe. In response to the increased interest in these materials, Brookhaven National Laboratory (BNL) has been engaged in a cooperative research program with the National Renewable Energy Laboratory (NREL), the Fraunhofer Institute for Solid State Technology (IFT), the Institute of Ecotoxicity of the GSF Forschungszentrum fair Umwelt und Gesundheit, and the National Institute of Environmental Health Sciences (NIEHS) to develop fundamental toxicological and environmental data for these three compounds. This workshop report describes the results of these studies and describes their potential implications with respect to the EH&S risks presented by CIS, CGS, and CdTe module production, use and decommissioning.
Date: April 28, 1994
Creator: Moskowitz, P.D.; Zweibel, K. & DePhillips, M.P.
Partner: UNT Libraries Government Documents Department

Investigation of polycrystalline thin film CuInSe{sub 2} solar cells based on ZnSe windows. Annual subcontract report, 15 February, 1993--14 February, 1994

Description: This report concerns studies of CIS solar cells based on ZnSe window layers. ZnSe/CIS devices are fabricated by growing ZnSe films by MOCVD onto Siemens CIS and graded absorber substrates. ZnSe films are grown by reacting H{sub 2}Se with a zinc adduct. ZnSe/CIS heterojunctions have been studied by depositing transparent aluminum contacts onto ZnSe. These studies indicate that ZnSe/CIS solar cells can be fabricated with an efficiency greater than 14%. Open circuit voltages are typically larger than 500 mV and the optimum range of ZnSe film thickness for maximum efficiency is between 100 {angstrom} and 250 {angstrom}. Photocurrents are significantly reduced as the film thickness exceeds 250 {angstrom}. Photoluminescence spectroscopy has been utilized to characterize the physical nature of CIS substrate surfaces, and ZnSe-CIS interfaces. These studies indicate that a segregated phase(s) exists at the surface of as received Siemens substrates. Additionally, it is determined that the segregated phase(s) still exist after the ZnSe growth process. To date, sputtered ZnO top contact layers have caused degradation of the photovoltaic properties of the ZnSe/CIS structure. Investigations of the effects of MOCVD grown ZnO upon ZnSe/CIS structures will soon be initiated. To establish the feasibility of ZnSe as a window layer, cells have been fabricated by incorporating a protective layer of CdS between the ZnSe and ZnO. A total area efficiency of 11% was obtained with such a structure.
Date: March 1, 1995
Creator: Olsen, L.C.
Partner: UNT Libraries Government Documents Department

Environmental, health and safety issues related to commercializing CuInSe{sub 2}-based photovoltaics

Description: Photovoltaics technology is rapidly evolving towards a new generation of low-cost thin film technologies. One of the most promising materials in this new generation is copper indium selenide (CuInSe{sub 2} or CIS). As with any new material, successful commercialization of CIS photovoltaic (PV) technology will require attention to environmental, health and safety issues, including consideration of the sources, usage, and end-of-product-life disposal and/or recycling of the constituent materials. This work focuses on three specific environmental, health and safety (EH and S) issues related to CIS PV: (1) economics are analyzed to determine their impact on materials use and re-use; (2) Federal and California State environmental disposal and waste handling regulations are analyzed to evaluate their impact on PV module manufacturing and end-of-life module handling; and (3) the logistics and economics of product recycling and waste disposal by industries with comparable EH and S issues are examined to quantify the corresponding options available for handling, disposing of and/or recycling manufacturing by-products and end-of-life modules.
Date: July 1, 1996
Creator: Eberspacher, C.; Fthenakis, V.M. & Moskowtiz, P.D.
Partner: UNT Libraries Government Documents Department

Research on polycrystalline thin-film submodules based on CuInSe{sub 2} materials. Final technical report, 14 December 1995--31 December 1996

Description: This report describes the progress made at Solarex for both device and module efficiencies from the inception of the CIS research program to the present. A rapid improvement in efficiency is apparent, culminating in the fabrication of a 15.5%-efficient device (total area) and a 13%-efficient submodule (aperture area). The device represents the highest efficiency device measured by NREL for any industrial source at that time. The module represented a new world record for any thin-film module at the time of its measurement. The factors leading to these results included improvements in absorber layer quality, transparent contacts, scribing and module formation processes. Other elements critical to the commercialization of CIS-based photovoltaics were also successfully attacked, including reduction of absorber deposition times into the range of 10 to 20 minutes and the successful scale-up of the absorber deposition process to greater than 500 cm{sup 2}. Other requisite processes saw continued development, such as a rapid, low-cost method for transparent window deposition. Subsequent to the demonstration of 13% module efficiency, scribing techniques were further improved that resulted in a reduction in shunt losses and higher module fill factor. This improvement, and the concomitant gain in fill factor, would yield efficiencies approaching 14% on modules having a short-circuit and open-circuit voltage comparable to the record module.
Date: April 1, 1997
Creator: Arya, R.; Fogleboch, J.; Kessler, J.; Russell, L.; Skibo, S. & Wiedeman, S.
Partner: UNT Libraries Government Documents Department

Photovoltaic Energy Program overview, fiscal year 1997

Description: The US Department of Energy (DOE) Photovoltaic Energy Program fosters the widespread acceptance of photovoltaic (PV) technology and accelerates commercial use of US PV products. The Program is founded on a collaborative strategy involving industry, the research and development community, potential users, utilities, and state and federal agencies. There are three main Program elements: Systems Engineering and Applications, Technology Development, and Research and Development.
Date: February 1, 1998
Partner: UNT Libraries Government Documents Department

Application of CIS to high-efficiency PV module fabrication. Phase 3 final technical report

Description: During this research period, researchers at International Solar Electric Technology (ISET) concentrated their efforts on three different areas of research. Within the National CIS R and D Team, ISET participated in the substrate/Mo interactions working group and investigated issues such as Na diffusion from the soda-lime glass substrate into the Mo layers and CIS films. Researchers determined that the Na content within the Mo layers was not a strong function of the nature of the Mo film. However, they found that diffusion through the Mo layers was a function of the Mo film characteristics as well as a very strong function of the CIS growth process itself. Researchers showed conclusively that the Na resided on the grain boundaries of CIS layers. Another team activity involved evaluation of CdS-free CIS solar cells. ZnO/CIS junctions prepared by the two-stage process showed light-soaking effects. Cells left under illumination improved in efficiency and were similar to the CdS/CIS junctions. After storage in the dark, however, efficiency deteriorated greatly for the ZnO/CIS device, most of the decline coming from the open-circuit voltage values. Much of the effort during this period was spent on developing a low-cost, non-vacuum CIS deposition technique. The method developed involves particulate deposition and formation of precursor layers followed by the conversion of these layers into CIS. Test modules of 40--60 cm{sup 2} were adapted to understand the issues involved in this novel technology. At the present time, the submodule efficiencies are 6--7%. Single-cell efficiencies are in the 10--13% range.
Date: August 1, 1998
Creator: Basol, B.M.; Kapur, V.K.; Leidholm, C.R.; Halani, A.; Roe, R. & Norsworthy, G.
Partner: UNT Libraries Government Documents Department

NCPV preprints for the 2. world conference on photovoltaic solar energy conversion

Description: The proceedings contain 26 papers arranged under the following topical sections: Silicon (3 papers); Thin-film PV technologies (11 papers): amorphous silicon, cadmium telluride, copper indium diselenide, and high efficiency devices; Module and BOS manufacturing (2 papers); Cell, module, and system testing (7 papers); and Market development (3 papers). Selected papers have been indexed separately for inclusion in the Energy Science and Technology Database.
Date: September 1, 1998
Partner: UNT Libraries Government Documents Department

Ninth workshop on crystalline silicon solar cell materials and processes: Summary discussion sessions

Description: This report is a summary of the panel discussions included with the Ninth Workshop on Crystalline Silicon Solar Cell Materials and Processes. The theme for the workshop was ``R and D Challenges and Opportunities in Si Photovoltaics.'' This theme was chosen because it appropriately reflects a host of challenges that the growing production of Si photovoltaics will be facing in the new millennium. The anticipated challenges will arise in developing strategies for cost reduction, increased production, higher throughput per manufacturing line, new sources of low-cost Si, and the introduction of new manufacturing processes for cell production. At the same time, technologies based on CdTe and CIS will come on line posing new competition. With these challenges come new opportunities for Si PV to wean itself from the microelectronics industry, to embark on a more aggressive program in thin-film Si solar cells, and to try new approaches to process monitoring.
Date: November 23, 1999
Creator: Sopori, B.; Tan, T.; Swanson, D.; Rosenblum, M. & Sinton, R.
Partner: UNT Libraries Government Documents Department

Commercialization of CIS-based thin-film PV: Phase 1 annual technical status report, August 1998--August 1999

Description: Outstanding progress toward reaching NREL/DOE goals was achieved during this subcontract: (1) Siemens Solar Industries (SSI) introduced two new CIS products to the SSI ST family of products, including an approximately 1-ft {times} 4-ft, 40-Wp module. (2) Process data for the production of circuit plates for the CIS family of products demonstrates improved efficiency and exhibits generally good control for extended periods. (3) The first subcontract milestone and the deliverables for this subcontract phase were met by delivering product samples that are larger and of higher efficiency than originally promised for this subcontract phase. (4) Capacity has been increased while also increasing the average efficiency of 1-ft {times} 4-ft circuit plates from 10.8% to 11.2%. (5) Yield improvements have been made by implementing improvements in processes and manufacturing protocols. (6) FM and UL approval was obtained for the ST series of products. (7) Long-term outdoor stability has been demonstrated at NREL, where 30-cm {times} 30-cm and 30-cm {times} 120-cm modules have undergone testing for more than 11 years. (8) SSI is addressing near-term and longer-term R&D topics through SSI's participation in NREL CIS National Team activities. (9) NREL confirmed a world-record 12.1% conversion efficiency large-area (3651 cm{sup 2}) CIS module. (10) R&D Magazine awarded the prestigious R&D 100 Award to SSI, NREL, and the California Energy Commission for the SSI family of CIS modules. CIS has demonstrated the prerequisites for a commitment to large-scale commercialization - high efficiency, long-term outdoor stability, and attractive cost projections. Remaining challenges are to: scale the processes to even larger areas, reach higher production capacity, demonstrate in-service durability over even longer times, and advance the fundamental understanding of CIS-based materials and devices, with the goal of further efficiency improvements for future products.
Date: June 29, 2000
Creator: Tarrant, D. E. & Gay, R. R.
Partner: UNT Libraries Government Documents Department

Fundamental studies of the effect of crystal defects on CuInSe{sub 2}/CdS heterojunction behavior: Final report, 28 June 1993--30 June 1998

Description: This report describes the work performed by the University of Illinois at Urbana-Champaign. The following results were obtained under the work funded by this subcontract: (1) Point defects and electronic properties of Cu(In{sub 1-x}Ga{sub x})Se{sub 2}: New record results for hole mobilities in Cu(In{sub 1-x}Ga{sub x})Se{sub 2} based on single crystals grown by Rockett's group; Demonstrated the role of Ga in determining hole concentrations; Showed that Ga does not affect the hole mobility in this material and why this is the case; Determined the diffusion coefficient for Ga in single-crystal Cu(In{sub 1-x}Ga{sub x})Se{sub 2}; Demonstrated the structure and optoelectronic properties of the CuIn{sub 3}Se{sub 5} ordered-defect phase of CuInSe{sub 2}; Characterized the detailed effects of Na on Cu(In{sub 1-x}Ga{sub x})Se{sub 2} solar cells and on the fundamental properties of the material itself (reduces compensating donors in p-type materials); and In collaboration with groups at the Universities of Salford and Liverpool in the United Kingdom, studied the effect of ion implantation damage on Cu(In{sub 1-x}Ga{sub x})Se{sub 2} single-crystals. (2) Materials for and characterization of devices: Developed a novel contact metallurgy that improves adhesion to the underlying Mo back-contact in solar cells made with Cu(In{sub 1-x}Ga{sub x})Se{sub 2}; (This material has also yielded substantial novel materials science behaviors, including grain rotation and growth prior to phase separation in a metastable binary alloy.) Characterized the electroluminescence as a function of temperature and Ga content in Cu(In{sub 1-x}Ga{sub x})Se{sub 2} solar cells and showed that the radiative recombination pathways are not band-to-band as in normal semiconductors, but rather, proceed through defect states; and Working with a group at the University of Uppsala in Sweden, demonstrated novel aspects of the bonding and chemistry of dip-coated CdS heterojunction materials used as heterojunction partner materials in Cu(In{sub 1-x}Ga{sub x})Se{sub 2} solar cells.
Date: November 17, 1999
Creator: Rockett, A.
Partner: UNT Libraries Government Documents Department