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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

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

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

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

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

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

Thin films: Past, present, future

Description: This report describes the characteristics of the thin film photovoltaic modules necessary for an acceptable rate of return for rural areas and underdeveloped countries. The topics of the paper include a development of goals of cost and performance for an acceptable PV system, a review of current technologies for meeting these goals, issues and opportunities in thin film technologies.
Date: April 1, 1995
Creator: Zweibel, K.
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

Novel thin-film CuInSe{sub 2} fabrication. Annual subcontract report, 1 May 1992--31 October 1993

Description: This report describes work exploring a new technique for the formation of Culn{sub x}Ga{sub 1{minus}x}Se{sub 2} thin films. The cu deposition was separated fro the Ga+In deposition such that precursor films with compositions of either Cu{sub x}Se or (In{sub x}Ga{sub 1{minus}x}){sub 2}Se{sub 3} were formed. These precursors were exposed to either (a) In+Ga+Se or (b) cu+Se at substrate temperatures > 500 C to form Galn{sub x}Ga{sub 1{minus}x}Se{sub 2}. Films made from the Cu{sub x}Se precursors were unexceptional, but films made from the (In{sub x}Ga{sub 1{minus}x}){sub 2}Se{sub 3} precursors were of exceptional smoothness and density. During the period covered in this report, a device made fro one of these films resulted in what, at the time, was the highest total-area efficiency measured for any non-single-crystal, thin-film solar cell, at 15.9%.
Date: August 1, 1994
Creator: Gabor, A. M. & Hermann, A. M.
Partner: UNT Libraries Government Documents Department

Low-cost CuInSe{sub 2} submodule development. Final subcontract report, 9 July 1990--31 January 1992

Description: Aim of this project is development and demonstration of processing steps necessary for fabrication of high efficiency CuInSe{sub 2} solar cells and sub-modules by the two-stage technique (also called the selenization method.) During this period, we have optimized the processing parameters of this method and demonstrated CuInSe{sub 2}/CdS/ZnO devices with a 1{endash}4 cm{sup 2} area and up to 12.4% active area efficiency. We have also developed a novel approach for the preparation of Cu/In precursors that improved the stoichiometric and morphological uniformity in these films. We have developed processing steps and tooling for handling up to 1 ft{sup 2} size substrates and as a result of these efforts demonstrated our first monolithically integrated sub-module of 1 ft{sup 2} area. 16 figs, 1 tab, 15 refs.
Date: October 1, 1992
Creator: Basol, B. M.; Kapur, V. K.; Halani, A. & Leidholm, C.
Partner: UNT Libraries Government Documents Department

Novel two-stage selenization methods for fabrication of thin-film CIS cells and submodules. Annual subcontract report, 25 March 1992--28 February 1993

Description: This is the Phase 1 Annual Technical Progress Report of a subcontract titled {open_quotes}Novel Two-Stage Selenization Methods for Fabrication of Thin-Film CIS Cells and Submodules.{close_quotes} The objectives of the program are the development of a cost effective process for CIS film deposition, optimization of various layers forming the CIS solar cell and fabrication of submodules using these processes and devices. During this first phase of the program the authors have completed their 1 ft{sup 2} size processing capabilities and added to their facilities an in-line sputtering system that can handle up to 1 ft{sup 2} size substrates. They have optimized the sputtering conditions for the Mo contact as well as the Cu and In films. Thickness uniformity of the Cu and In layers have also been optimized by masking the magnetron cathodes to obtain a variation of 3% throughout a ft{sup 2} substrate. Using the resulting films, they have demonstrated their first large area CIS submodules with outputs of about 3W/ft{sup 2}. Addition of a computer controlled mechanical scriber to the fabrication facilities, and optimization of the large-area ZnO layers are expected to improve the power output of these submodules to over 5W/ft{sup 2} shortly. In addition to the large-area submodule work, the authors have also carried out research aimed at the development of a non-vacuum processing approach for the growth of CIS layers. They have deposited films using this technique, and small-area cells with over 10% conversion efficiency have been demonstrated on such CIS layers.
Date: October 1, 1993
Creator: Basol, B. M.; Kapur, V. K.; Halani, A. & Leidholm, C.
Partner: UNT Libraries Government Documents Department

Advanced processing technology for high-efficiency thin-film CuInSe{sub 2} solar cells. Annual subcontract report, 1 March 1992--28 February 1993

Description: This report describes work to develop novel fabrication for CuInSe{sub 2} (CIS) solar cells that will result in improved performance and cost effectiveness at the manufacturing level. The primary approach involves all solid-state processing for CIS. This was augmented by work to provide novel alternatives for the formation of the window layer/heterojunction contact. Inherent to the project was the need to develop a generic understanding of the relationship between processing and performance so that broad-based transfer to industry can be facilitated. We achieved good-electronic-quality CIS by the use of two selenization procedures for predeposited metal layers. We achieved good stoichiometry throughout the bulk of the film, attained grain sizes of up to 1 {mu}m, and measured electron mobilities of up to 60 cm{sup 2}V-s. However, there is a complex relationship between grain size, adhesion, and performance. Our primary approach to characterization was to fabricate ZnO/CIS test devices and measure as many properties as possible in device format. We are also developing reactive sputtering of ZnO as an alternative window layer technology.
Date: August 1, 1993
Creator: Morel, D. L.; Attar, G.; Karthikeyan, S.; Muthaiah, A. & Zafar, A.
Partner: UNT Libraries Government Documents Department

Polycrystalline CuInSe{sub 2} and CdTe PV solar cells. Annual subcontract report, 15 April 1993--14 April 1994

Description: This is an annual technical report on the Phase 2 of a three-year phased research program. The principal objective of the research project is to develop novel and low-cost processes for the fabrication of stable and efficient CuIn{sub 1{minus}x}Ga{sub x}Se{sub 2} and CdTe polycrystalline-thin-film solar cells using reliable techniques amenable to scale-up for economic, large-scale manufacture. The aims are to develop a process for the non-toxic selenization so as to avoid the use of extremely toxic H{sub 2}Se in the fabrication of CuIn{sub 1{minus}x}Ga{sub x}Se{sub 2} thin-film solar cells; to optimize selenization parameters; to develop a process for the fabrication of CdTe solar cells using Cd and Te layers sputtered from elemental targets; to develop an integrated process for promoting the interdiffusion between Cd/Te layers, CdTe phase formation, grain growth, type conversion, and junction formation; to improve adhesion; to minimize residual stresses; to improve the metallic back-contact; to improve the uniformity, stoichiometry, and morphology of CuIn{sub 1{minus}x}Ga{sub x}Se{sub 2} and CdTe thin films; and to improve the efficiency of CuIn{sub 1{minus}x}Ga{sub x}Se{sub 2} and CdTe solar cells.
Date: November 1, 1994
Creator: Dhere, N. G.
Partner: UNT Libraries Government Documents Department

Non-H{sub 2}Se, ultra-thin CuInSe{sub 2} devices. Annual subcontract report, November 10, 1992--November 9, 1993

Description: This report describes advances made during Phase II (November 10, 1992-November 9, 1993) of a three-phase, cost-shared subcontract whose ultimate goal is the demonstration of thin film CuInSe{sub 2} photovoltaic modules prepared by methods adaptable to safe, high yield, high volume manufacturing. At the end of Phase I, EPV became one of the first groups to clear the 10% efficiency barrier for CIS cells prepared by non-H{sub 2}Se selenization. During Phase II a total area efficiency of 12.5% was achieved for a 1 cm{sup 2} cell. The key achievement of Phase II was the production of square foot CIS modules without the use of H{sub 2}Se. This is seen as a crucial step towards the commercialization of CIS. Using a novel interconnect technology, EPV delivered an 8.0% aperture area efficiency mini-module and a 6.2% aperture area efficiency 720 cm{sub 2} module to NREL. On the processing side, advances were made in precursor formation and the selenization profile, both of which contributed to higher quality CIS. The higher band gap quaternary chalcopyrite material CuIn(S{sub x}, Se{sub 1{minus}X}){sub 2} was prepared and 8% cells were fabricated using this material. Device analysis revealed a correlation between long wavelength quantum efficiency and the CIS Cu/In ratio. Temperature dependent studies highlighted the need for high V{sub OC} devices to minimize the impact of the voltage drop at operating temperature. Numerical modeling of module performance was performed in order to identify the correct ZnO sheet resistance for modules. Efforts in Phase III will focus on increase of module efficiency to 9-10%, initiation of an outdoor testing program, preparation of completely uniform CIS plates using second generation selenization equipment, and exploration of alternative precursors for CIS formation.
Date: September 1, 1994
Creator: Delahoy, A. E.; Britt, J.; Faras, F. & Kiss, Z.
Partner: UNT Libraries Government Documents Department

Role of polycrystallinity in CdTe and CuInSe{sub 2} photovoltaic cells. Annual subcontract report, 1 April 1991--31 March 1992

Description: The limiting role of polycrystallinity in thin-film solar calls has been reduced somewhat during the past year, and efficiencies of both CdTe and CuInSe{sub 2} cells are approaching 15%. Quantitative separation of loss mechanisms shows that individual losses, with the exception of forward recombination current, can be made comparable to their single crystal counterparts. One general manifestation of the extraneous trapping states in that the voltage of all polycrystalline thin-film cells drifts upward by 10--50 mV following the onset of illumination.
Date: November 1, 1992
Creator: Sites, J. 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

Innovative sputtering techniques for CIS and CdTe submodule fabrication. Annual subcontract report, 1 September 1991--31 August 1992

Description: This report describes work done during Phase 1 of the subject subcontract. The subcontract was designed to study innovative deposition techniques, such as the rotating cylindrical magnetron sputtering system and electrodeposition for large-area, low-cost copper indium diselenide (CIS) and cadmium telluride (CdTe) devices. A key issue for photovoltaics (PV) in terrestrial and future space applications is producibility, particularly for applications using a large quantity of PV. Among the concerns for fabrication of polycrystalline thin-film PV, such as CIS and CdTe, are production volume, cost, and minimization of waste. Both rotating cylindrical magnetron (C-Mag{trademark}) sputtering and electrodeposition have tremendous potential for the fabrication of polycrystalline thin-film PV due to scaleability, efficient utilization of source materials, and inherently higher deposition rates. In the case of sputtering, the unique geometry of the C-Mae facilitates innovative cosputtering and reactive sputtering that could lead to greater throughput reduced health and safety risks, and, ultimately, lower fabrication cost. Electrodeposited films appear to be adherent and comparable with low-cost fabrication techniques. Phase I involved the initial film and device fabrication using the two techniques mentioned herein. Devices were tested by both internal facilities, as well as NREL and ISET.
Date: March 1, 1993
Creator: Armstrong, J. M.; Misra, M. S. & Lanning, B.
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