This report describes research to fabricate high-efficiency CdZnS/CuInGaSe{sub 2} (CIGS) thin-film solar cells, and to develop improved transparent conductor window layers such as ZnO. A specific technical milestone was the demonstration of an air mass (AM) 1.5 global, 13% efficient, 1-cm{sup 2}-total-area CIGS thin-film solar cell. Our activities focused on three areas. First, a CIGS deposition: system was modified to double its substrate capacity, thus increasing throughput, which is critical to speeding the process development by providing multiple substrates from the same CIGS run. Second, new tooling was developed to enable an investigation of a modified aqueous CdZnS process. The goal was to improve the yield of this critical step in the device fabrication process. Third, our ZnO sputtering system was upgraded to improve its reliability, and the sputtering parameters were further optimized to improve its properties as a transparent conducting oxide. The characterization of the new CIGS deposition system substrate fixturing was completed, and we produced good thermal uniformity and adequately high temperatures for device-quality CIGS deposition. Both the CIGS and ZnO deposition processes were refined to yield a ZnO//Cd{sub 0.82}Zn{sub 0.18}S/CuIn{sub 0.80}Ga{sub 0.20}Se{sub 2} cell that was verified at NREL under standard testing conditions at 13.1% efficiency with V{sub oc} = 0.581 V, J{sub sc} = 34.8 mA/cm{sup 2}, FF = 0.728, and a cell area of 0.979 cm{sup 2}.

Polycrystalline thin-film solar cells with the structure ZnO/CdZnS/CuInGaSe/sub 2/ have been fabricated with larger single-cell areas than have been previously reported. A cell with an area of 4 cm/sup 2/ has been made with an AM1.5, 100 mW/cm/sup 2/ total area conversion efficiency of 11.1% (12.0% active area) and an AM0 conversion efficiency of 10.0% (10.9% active area). The CuInGaSe/sub 2/ layer had a gallium to indium ratio of 0.26:0.74 with a bandgap of approximately 1.15 eV. The cells use an isolated tab design for the negative (grid) contact, demonstrating the ability to pattern the semiconductor layers. Such CuInGaSe/sub 2/-based cells may be suitable for large-area terrestrial applications and for single-junction space cell applications.< >

The results of a two year research programs are presented. A 1- cm{sup 2} ZnO/CdZnS/CuInGaSe{sup 2} solar cell with a total area efficiency of 12.5% (12.9% active area) as measured at SERI (AM1.5, 100 mW/cm{sup 2}) has been fabricated. The quantum efficiency of this device at 400 nm is over 0.7 due to the improved transmission of the ZnO/thin CdZnS window layers. The fabrication and characteristics of each of the three layers and of the complete devices are discussed. An extensive optical analysis of this cell has been done. This analysis is presented and the implications for cell performance discussed. A 4 cm{sup 2} cell with this same structure has been fabricated with an efficiency of 11.1% (11.9% active area), again as measured at SERI. The I-V and Quantum Efficiency characteristics of this cell are presented and the reasons for the decreased conversion efficiency relative to the 1-cm{sup 2}cells are discussed. 28 refs., 24 figs., 3 tabs.

Thin-film polycrystalline solar cells with the structure ZnO/CdZnS/CuInGaSe/sub 2/ fabricated with total area efficiencies of up to 12.5% under AM1.5 equivalent illumination and 10.5% under AM0 equivalent are discussed. These are among the highest total area efficiencies reported for polycrystalline thin-film solar cells. Current-voltage and quantum efficiency data for such a high-efficiency cell ...

The properties of polycrystalline, thin-film CuInSe/sub 2//CdS and CuInSe/sub 2//(Cd,Zn)S solar cells prepared by vacuum evaporation techniques are described. First results are presented on preparation of CuIn/sub 1-x/Ga/sub x/Se/sub 2/ polycrystalline thin-films and CuIn/sub 1-x/Se/sub 2//CdS photovoltaic devices. X-ray diffraction and photoluminescence results on the films are given. Current-voltage and spectral response measurements are reported on CuIn/sub 1-x/Ga/sub x/Se/sub 2//CdS devices that show the higher V/sub oc/ and wider band gap expected. Experiments on annealing of CuInSe/sub 2/ in H/sub 2/Se which produced grain sizes of up to 20 ..mu..m are reported. Thermally stimulated capacitance, isothermal capacitance transient spectroscopy, and a new transient capacitance technique applied to CuInSe/sub 2//CdS cells are described. Application of film and device analysis techniques (SEM, EDS, EBIC, and laser spot scans) are described. Low-temperature photoluminescence of CuInSe/sub 2/ films is discussed along with a proposed energy level model. Results of epitaxial deposition, ionized cluster beam deposition, and deposition of CuInSe/sub 2/ in an oxygen ambient are discussed. Loss analysis results and reports pertaining to cell analysis and theoretical cell mechanism studies are presented.