Advanced Processing of CdTe- and CuInxGa1-xSe2-Based Solar Cells: Final Report, 18 April 1995 - 31 May 1998

This report summarizes work performed by the University of South Florida Department of Electrical Engineering under this subcontract. The cadmium telluride (CdTe) portion of this project deals with the development of high-efficiency thin-film CdTe solar cells using fabrication techniques that are suitable for manufacturing environments. The process being developed for semiconductor deposiiton isclose-spaced sublimation (CSS), which has demonstrated high throughput and efficient material utilization. During Phase II, an all-CSS device fabricated on Libbey-Owens-Ford substrate exhibited a 14.3% efficiency. Alternative transparent conducting oxides (TCOs) and window materials being studied under this project include zinc oxide (ZnO) and zinc selenide (ZnSe). The best efficiency obtainedfor a ZnSe/CdTe device was 11.3%. This work also included fabricating CdTe solar cells heat-treated with CdCl2 vapor instead of the typical methanol/CdCl2 wet process, which has produced some encouraging results. The copper indium gallium diselenide (CIGS) portion of the project focused on developing a semiconductor that reliably and reproducibly produced high Jsc values. A key objective wasachieved: the ability to optimize bulk and surface properties independently of each other. Researchers were able to boosst Voc values above 500 mV on 40 mA/m2 base materials and achieve efficiencies of 13%