Toward High Performance Epitaxial and Low-temperature Cu ( In , Ga ) Se 2 Solar Cells
The CIGS research effort at the University of Illinois represents a three-pronged approach to understanding and solving some of the most critical issues in CIGS device. These three prongs are: (1) development of a basic understanding of the issues limiting performance in CIGS devices, (2) advancing the performance of the devices through single crystal epitaxial layers for integration into high-performance cells, and (3) developing novel growth processes that will allow lower deposition temperatures necessary to multijunction devices. This paper presents an approach for CIGS/GaAs and CIGS/Ge heterojunction solar cells for multijunction high-efficiency devices. In addition, application of ionized physical vapor deposition to lowtemperature deposition of CIGS is described. The two projects will be coupled and results from one used to enhance progress in the other as part of the Beyond the Horizon and High Performance PV programs now starting.
Single crystal and polycrystalline CuInSe/sub 2/ by the hybrid sputtering and evaporation method
Polycrystalline and single-crystal CuInSe/sub 2/ has been grown by the hybrid sputtering and evaporation process. The solar cells were 0.08 cm/sup 2/. The maximum conversion efficiency recorded was 8.4% with V/sub oc/=392 mV, J/sub SC/=33.9 mA, and a fill factor of 63.1%. Single-crystal CuInSe/sub 2/ thin films were deposited on GaAs
Chemical and structural characterization of physical‐vapor deposited CuInSe2 for solar cell applications
This paper reports the results of a comparative study of chalcopyrite‐structure CuInSe2 deposited by three techniques, three‐source evaporation, reactive sputtering and a hybrid sputtering, and evaporation method. All films exhibit comparable microstructures and microchemistries. Evaporated and hybrid‐process films include significant porosity. All layers show dislocations, twins, and stacking faults. No second phases were observed in layers deposited by any of the techniques, independent of film composition. Data supporting this conclusion include average and single‐grain energy‐dispersive x‐ray fluorescence spectroscopy measurements, diffraction studies of the film structure, and transmission electron microscopy images of the films. Finally, grain sizes can be increased by annealing films at temperatures above 400 °C.