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A new optical parametric amplifier based on lithium thioindate used for sum frequency generation vibrational spectroscopic studies of the Amide I mode of an interfacial model peptide

Description: We describe a new optical parametric amplifier (OPA) that employs lithium thioindate, LiInS{sub 2} (LIS), to create tunable infrared light between 1500 cm{sup -1} and 2000 cm{sup -1}. The OPA based on LIS described within provides intense infrared light with a good beam profile relative to similar OPAs built on silver gallium sulfide, AgGaS{sub 2} (AGS), or silver gallium selenide, AgGaSe{sub 2} (AGSe). We have used the new LIS OPA to perform surface-specific sum frequency generation (SFG) vibrational spectroscopy of the amide I vibrational mode of a model peptide at the hydrophobic deuterated polystyrene (d{sub 8}-PS)-phosphate buffered saline interface. This model polypeptide (which is known to be an ?-helix in the bulk solution under the high ionic strength conditions employed here) contains hydrophobic leucyl (L) residues and hydrophilic lysyl (K) residues, with sequence Ac-LKKLLKLLKKLLKL-NH{sub 2}. The amide I mode at the d{sub 8}-PS-buffer interface was found to be centered around 1655 cm{sup -1}. This can be interpreted as the peptide having maintained its {alpha}-helical structure when adsorbed on the hydrophobic surface, although other interpretations are discussed.
Date: May 3, 2008
Creator: York, Roger L.; Holinga, George J.; Guyer, Dean R.; McCrea, Keith R.; Ward, Robert S. & Somorjai, Gabor A.
Partner: UNT Libraries Government Documents Department

Crystal chemistry and self-lubricating properties of monochalcogenides gallium selenide and tin selenide

Description: This paper describes the fundamentals of the crystal chemistry and self-lubricating mechanisms of two monochalcogenides; tin selenide and gallium selenide. Specifically, it enumerates their inter-atomic array and bond structure in crystalline states, and correlates this fundamental knowledge with their self-lubricating capacity. Friction tests assessing the self-lubricating performance of gallium and tin selenides were carried out on a pin-on-disk machine. Specifically, large crystalline pieces of gallium selenide and tin selenide were cut and cleaved into flat squares and subsequently rubbed against the sapphire balls. In another case, the fine powders (particle size {approx} 50--100 {mu}m) of gallium selenide and tin selenide were manually fed into the sliding interfaces of 440C pins and 440C disks. For the specific test conditions explored, it was found that the friction coefficients of the sapphire/gallium selenide and sapphire/tin selenide pairs were {approx} 0.23 and {approx} 0.35, respectively. The friction coefficients of 440C pin/440C disk test pairs with gallium selenide and tin selenide powders were on the orders of {approx} 0.22 and {approx} 0.38, respectively. For comparison, a number of parallel friction tests were performed with MoS{sub 2} powders and compacts and the results of these tests were also reported. The friction data together with the crystal-chemical knowledge and the electron microscopic evidence supported the conclusion that the lubricity and self-lubricating mechanisms of these solids are closely related to their crystal chemistry and the nature of interlayer bonding.
Date: February 1, 1993
Creator: Erdemir, A.
Partner: UNT Libraries Government Documents Department

Deep levels in AgGaSe{sub 2}

Description: The photoluminescence spectra of AgGaSe{sub 2} obtained at 77 K is reported. Two emission peaks have been observed and their pressure dependence studied. One of these peaks has been identified with emission involving one of the two deep level peak D{sub 1} and D{sub 2} observed previously in absorption measurement [App. Phys. Lett. 64,1717 (1994)]. A simple model for the capture of carriers into these deep levels has been proposed.
Date: August 1, 1994
Creator: Choi, I. H. & Yu, P. Y.
Partner: UNT Libraries Government Documents Department

Final Report

Description: The objective of this DOE SAI project is to demonstrate the feasibility of electrodeposited and solution-doped transparent conducting oxides (TCOs) such as zinc oxide with resistivity in the mid-10{sup -4} {Omega}-cm range. The target application is an 'on-top' TCO which can be deposited on semiconductors in thin-film and future solar cells including amorphous silicon, copper indium gallium selenide and emerging solar cells. There is no solution-prepared on-top TCO currently used in commercial solar cells. This project, if successful, will fill this gap. Our technical objectives include electrodeposited TCOs with (1) resistivity in the mid-10{sup -4} {Omega}-cm range, (2) post-deposition annealing below 300 C and (3) no-vacuum processing or low-vacuum processing. All the three research objectives listed above have been accomplished in the 14-month period from July 1, 2009 through September 30, 2010. The most noticeable accomplishments of this project are (1) identification of a terawatt-scale dopant for zinc oxide, i.e. yttrium, whose known reserve is enough for 60 peak terawatts of thin-film solar cells; (2) demonstration of a record-low resistivity, 6.3 x 10{sup -5} {Omega}-cm, in solution-deposited zinc oxide with an abundant dopant; and (3) the record-low resistivity was accomplished with a maximum process temperature of 300 C and without vacuum annealing. Industrial applications of the new yttrium-doped zinc oxide are being pursued, including (1) green deposition of yttrium-doped zinc oxide to reduce water consumption during deposition and (2) search for an industrial partner to develop an electrochemical tool for large-area uniform deposition of yttrium-doped zinc oxide.
Date: December 22, 2010
Creator: Tao, Dr. Meng
Partner: UNT Libraries Government Documents Department

CIS photovoltaic technology. Annual technical report, January 12, 1996--January 11, 1997

Description: Thin film photovoltaic modules based on Cu(In,Ga)Se{sub 2} have been shown to possess attributes that should enable them to compete effectively with silicon-based modules, and that should ultimately allow realization of a much lower $/Wp cost figure. These attributes are stability, high efficiency, and low materials cost. Energy Photovoltaics has explored novel CIGS formation recipes that can be implemented on a unique pilot line constructed to coat substrates 4300 cm{sup 2} in area. One particular feature of this line is the use of proprietary linear sources capable of downwards evaporation. After experimentation with several types of recipe, a so-called {open_quotes}hybrid{close_quotes} process was found to simultaneously yield the desired combination of properties, namely good adhesion, device efficiency, uniformity, and reproducibility. The steps involve precursor formation, compound formation, and termination. Diagnostic techniques used to study and improve the CIGS films included spatial mapping of thickness, composition (using Auger analysis), resistance, V{sub oc} and I{sub sc}. The last three items are determined by quick tests designed to provide rapid feedback on plate quality. Problem areas were broken down and isolated through use of techniques involving substitution of different pieces of equipment for certain processing steps. For example, pilot line precursors were selenized in both the pilot line and smaller scale R&D equipment.
Date: June 1, 1997
Creator: Delahoy, A.E.; Britt, J.S. & Kiss, Z.J.
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

Derived reference doses for three compounds used in the photovoltaics industry: Copper indium diselenide, copper gallium diselenide, and cadmium telluride

Description: Polycrystalline thin-film photovoltaic modules made from copper indium diselenide (CIS), copper gallium diselenide (CGS), and cadmium telluride (CdTe) arc nearing commercial development. A wide range of issues are being examined as these materials move from the laboratory to large-scale production facilities to ensure their commercial success. Issues of traditional interest include module efficiency, stability and cost. More recently, there is increased focus given to environmental, health and safety issues surrounding the commercialization of these same devices. An examination of the toxicological properties of these materials, and their chemical parents is fundamental to this discussion. Chemicals that can present large hazards to human health or the environment are regulated often more strictly than those that are less hazardous. Stricter control over how these materials are handled and disposed can increase the costs associated with the production and use of these modules dramatically. Similarly, public perception can be strongly influenced by the inherent biological hazard that these materials possess. Thus, this report: presents a brief background tutorial on how toxicological data are developed and used; overviews the toxicological data available for CIS, CGS and CdTe; develops ``reference doses`` for each of these compounds; compares the reference doses for these compounds with those of their parents; discusses the implications of these findings to photovoltaics industry.
Date: July 6, 1995
Creator: Moskowitz, P.D.; Bernholc, N.; DePhillips, M.P. & Viren, J.
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

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

Influence of Damp Heat on the Electrical, Optical, and Morphological Properties of Encapsulated CuInGaSe2 Devices: Preprint

Description: CuInGaSe2 (CIGS) devices, encapsulated with different backsheets having different water vapor transmission rates (WVTR), were exposed to damp heat (DH) at 85C and 85% relative humidity (RH) and characterized periodically to understand junction degradation induced by moisture ingress. Performance degradation of the devices was primarily driven by an increase in series resistance within first 50 h of exposure, resulting in a decrease in fill factor and, accompanied loss in carrier concentration and widening of depletion width. Surface analysis of the devices after 700-h DH exposure showed the formation of Zn(OH)2 from hydrolysis of the Al-doped ZnO (AZO) window layer by the moisture, which was detrimental to the collection of minority carriers. Minority carrier lifetimes observed for the CIGS devices using time resolved photoluminescence (TRPL) remained relatively long after DH exposure. By etching the DH-exposed devices and re-fabricating with new component layers, the performance of reworked devices improved significantly, further indicating that DH-induced degradation of the AZO layer and/or the CdS buffer was the primary performance-degrading factor.
Date: August 1, 2011
Creator: Sundaramoorthy, R.; Pern, F. J.; Teeter, G.; Li, J. V.; Young, M.; Kuciauskas, D. et al.
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

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

A low-cost approach to fabrication of multinary compounds for energy-related applications

Description: Non-vacuum electrodeposition and electroless deposition techniques with a potential to prepare large-area uniform precursor films using low-cost source materials and low-cost capital equipment are very attractive for the growth of compound materials for superconductors and photovoltaic applications. In the first part, a low-cost electrodeposition (ED) method will be discussed for fabrication of high-temperature Tl-oxide-based superconductors. In the second part, electrodeposition and electroless deposition of semiconductor Cu-In-Ga-Se thin films will be discussed.
Date: January 3, 2000
Creator: Bhattacharya, R.N. & Deb, S.K.
Partner: UNT Libraries Government Documents Department

Preferred orientation in polycrystalline Cu(In,Ga)Se{sub 2} and its effect on absorber thin-films and devices

Description: The purpose of this work is to investigate physical properties of Cu(In,Ga)Se{sub 2} polycrystalline thin-films exhibiting a high degree of preferred orientation. Specifically, by using Na-free Cu(In,Ga)Se{sub 2} thin-films, it is intended to experimentally determine differences (if any) between films with a (110/102)-preferred orientation and films with a (112)-preferred orientation. The approach to the problem is a systematic comparative analysis of film and device properties in which the most significant variable is the preferred orientation of the Cu(In,Ga)Se{sub 2} polycrystalline absorbers. To complement the results of Na-free absorbers and devices, a microstructural analysis is presented on (110)-oriented high efficiency Cu(In,Ga)Se{sub 2} absorbers that are grown on standard Mo-coated soda-lime glass substrates.
Date: May 15, 2000
Creator: Contreras, M. A.; Jones, K. M.; Gedvilas, L. & Matson, R.
Partner: UNT Libraries Government Documents Department

Processing and modeling issues for thin-film solar cell devices: Annual subcontract report, January 16, 1995 -- January 15, 1996

Description: The overall mission of the Institute of Energy Conversion is the development of thin film photovoltaic cells, modules, and related manufacturing technology and the education of students and professionals in photovoltaic technology. The objectives of this four-year NREL subcontract are to advance the state of the art and the acceptance of thin film PV modules in the areas of improved technology for thin film deposition, device fabrication, and material and device characterization and modeling, relating to solar cells based on CuInSe{sub 2} and its alloys, on a-Si and its alloys, and on CdTe. In the area of CuInSe{sub 2} and its alloys, EEC researchers have produced CuIn{sub 1-x}GaxSe{sub 2} films by selenization of elemental and alloyed films with H{sub 2}Se and Se vapor and by a wide variety of process variations employing co-evaporation of the elements. Careful design, execution and analysis of these experiments has led to an improved understanding of the reaction chemistry involved, including estimations of the reaction rate constants. Investigation of device fabrication has also included studies of the processing of the Mo, US and ZnO deposition parameters and their influence on device properties. An indication of the success of these procedures was the fabrication of a 15% efficiency CuIn{sub 1-x}GaxSe{sub 2} solar cell.
Date: August 1, 1996
Creator: Birkmire, R.W.; Phillips, J.E.; Buchanan, W.A.; Eser, E.; Hegedus, S.S.; McCandless, B.E. et al.
Partner: UNT Libraries Government Documents Department

CIS photovoltaic technology. Annual technical report, January 12, 1995--January 11, 1996

Description: EPV`s overall strategy in developing CIGS photovoltaic technology has been to define and construct a flexible set of large area vacuum deposition equipment and to explore CIGS formation recipes that can be implemented on this equipment. This is the inverse of the conventional approach in which manufacturing techniques are sought that can reproduce a high efficiency laboratory scale process over large areas. A feature of this equipment is the use of proprietary linear sources capable of downwards evaporation. Using recipes generated within this program, CIGS cells with efficiencies up to 13.9% were prepared by EPV under a separate CRADA with NREL. Entirely within this program, an aperture area efficiency of 9.6% was achieved for a laminated submodule of area 135.2 cm{sup 2}. Considerable effort has gone into the preparation and characterization of CIGS prepared on substrates measuring 96.5 cm x 44.5 cm, and good compositional uniformity has been achieved along both the short and long directions of the plate. Despite this, the material has not yet achieved the efficiency levels demonstrated in smaller scale equipment, and recipe development is ongoing. As part of a program to eliminate, if possible, the use of CdS, alternative buffer layers such as InSe, In{sub x}S{sub y}, and ZnSe have been explored, and, to gain insight into junction formation, CdSe. Of these compounds, ZnSe has shown the most promise, and further experiments are being conducted to optimize material and device properties.
Date: June 1, 1996
Creator: Delahoy, A.E.; Britt, J.S. & Gabor, A.M.
Partner: UNT Libraries Government Documents Department

Device physics of thin-film polycrystalline cells and modules: Phase 1 annual report: February 1998--January 1999

Description: This report describes work done by Colorado State University (CSU) during Phase 1 of this subcontract. CSU researchers continued to make basic measurements on CI(G)S and CdTe solar cells fabricated at different labs, to quantitatively deduce the loss mechanisms in these cells, and to make appropriate comparisons that illuminate where progress is being made. Cells evaluated included the new record CIGS cell, CIS cells made with and without CdS, and those made by electrodeposition and electroless growth from solution. Work on the role of impurities focused on sodium in CIS. Cells with varying amounts of sodium added during CIS deposition were fabricated at NREL using four types of substrates. The best performance was achieved with 10{sup {minus}2}--10{sup {minus}1} at% sodium, and the relative merits of proposed mechanisms for the sodium effect were compared. Researchers also worked on the construction and testing of a fine-focused laser-beam apparatus to measure local variations in polycrystalline cell performance. A 1{micro}m spot was achieved, spatial reproducibility in one and two dimensions is less than 1 {micro}m, and photocurrent is reliably measured when the 1{micro}m spot is reduced as low as 1-sun in intensity. In elevated-temperature stress tests, typical CdTe cells held at 100 C under illumination and normal resistive loads for extended periods of time were generally very stable; but those held under reverse or large forward bias and those contacted using larger amounts of copper were somewhat less stable. CdTe cell modeling produced reasonable fits to experimental data, including variations in back-contact barriers. A major challenge being addressed is the photovoltaic response of a single simple-geometry crystallite with realistic grain boundaries.
Date: December 21, 1999
Creator: Sites, J. R.
Partner: UNT Libraries Government Documents Department

Numericl modeling of graded band gap CIGS solar cells

Description: The high efficiency reported recently by NREL for CIGS solar cells demonstrates the potential of band gap grading in producing high efficiency thin film solar cells. In order to reap the full benefits of this design strategy, a clear understanding of the fundamental device physics of these structures is needed. The purpose of this paper is to examine the role grading of the band gap plays in achieving high conversion efficiencies. To aid in this examination, a detailed numerical device simulation program, ADEPT, is used.
Date: December 31, 1994
Creator: Gray, J.L. & Lee, Youn Jung
Partner: UNT Libraries Government Documents Department

Correlation of polycrystalline Cu(In,Ga)Se{sub 2} device efficiency with homojunction depth and interfacial structure: X-ray photoemission and positron annihilation spectroscopic characterization

Description: Angled-resolved high resolution photoemission measurements on valence band electronic structure and Cu 2p, In 3d, Ga 2p, and Se 3d core lines were used to evaluate surface and near-surface chemistry of CuInSe{sub 2} and Cu(In,Ga)Se{sub 2} device grade thin films. XPS compositional depth profiles were also acquired from the near-surface region, and bonding of the Cu, In, Ga, and Se was determined as a function of depth. A Cu-poor region was found, indicating CuIn{sub 5}Se{sub 8} or a CuIn{sub 3}Se{sub 5}-In{sub 2}Se{sub 3} mixture. Correlation between the depth of the Cu-poor region/bulk interface and device efficiency showed that the depth was 115 {angstrom} for a 16.4% CIGS device, 240 {angstrom} for a 15.0% CIGS, and 300 {angstrom} for 14.0% CIGS, with similar trends for CIS films. The surface region is n-type, the bulk is p-type, with a 0.5 eV valence band offset. Depth of homojunction may be the determining factor in device performance. Positron annihilation spectroscopy gave similarly illuminating results.
Date: June 1, 1994
Creator: Nelson, A. J.; Sobol, P. E.; Gabor, A. M.; Contreras, M. A.; Asoka-Kumar, P. & Lynn, K. G.
Partner: UNT Libraries Government Documents Department

Characterization of Damp-Heat Degradation of CuInGaSe2 Solar Cell Components and Devices by (Electrochemical) Impedance Spectroscopy: Preprint

Description: This work evaluated the capability of (electrochemical) impedance spectroscopy (IS, or ECIS as used here) to monitor damp heat (DH) stability of contact materials, CuInGaSe2 (CIGS) solar cell components, and devices. Cell characteristics and its variation of the CIGS devices were also examined by the ECIS.
Date: September 1, 2011
Creator: Pern, F. J. J. & Noufi, R.
Partner: UNT Libraries Government Documents Department