Materials analysis and device optimization of CuInSe sub 2 solar cells

This report presents results and conclusions from the two-year research program on CuInSe{sub 2} thin-film solar cells. The research was carried out in two integrated tasks: materials preparation and analysis, and high-efficiency solar cell fabrication and analysis. CuInSe{sub 2} thin-films were prepared by vacuum evaporation of elemental Cu, In, and Se onto heated substrates. We present systematic studies of the effects of incident flux and substrate temperature on CuInSe{sub 2} film composition and morphology. We prepared mirror smooth CuInSe{sub 2} films using a newly developed aqueous bromine solution as a chemical polishing etch, and we fabricated and analyzed heterojunction photovoltaic devices with (CdZn)S, ITO/ (CdZn)S, ZnO, and ZnO/(CdZn) window layer. We found the dominant recombination mechanism in high-efficiency CuInSe{sub 2} devices to be space-charge recombination in the CuInSe{sub 2}. We fabricated optimized one-square-centimeter CuInSe{sub 2}/(CdZn)S solar cells with efficiencies over 10%. 23 refs., 22 figs., 11 tabs.