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
Deposition of CuInSe/sub 2/ by the hybrid sputtering-and-evaporation method
The initial results of experiments characterizing CuInSe/sub 2/ deposition by a hybrid sputtering-and-evaporation technique are presented. The method yields films with compositions and structural properties comparable with those commonly accepted for polycrystalline CuInSe/sub 2/ over a large composition range at growth temperatures up to 450 degrees C. Film compositions are uniform to within +or-1 atomic percent, and nonuniformities can be directly related to the deposition geometry. The Se flux is shown to play a major role in determining both the Se and the In contents of the films at elevated temperatures. The substrate properties strongly affect the film composition. Layers deposited on sputtered Mo surfaces exhibit a lower In content than films on glass at all temperatures examined. Cu, In, and Se diffusion into the column boundaries of the Mo substrates is observed at all growth temperatures.<<ETX>>