Thin-film photovoltaics

CdTe and CuIn1-xGaxSe2-ySy (CIGSS) are ideal candidates for thin-film solar cells. Present photovoltaic (PV) conversion efficiencies of champion thin-film solar cells are: CuIn1-xGaxSe2 (CIGS) 19.5%, CdTe 16.5%, and a-Si: H 12.4%. Thin-film PV modules could spearhead production growth of photovoltaics in the United States because of their added production capacity. For this purpose, module efficiencies must be improved to the 13%-15% range. Obtaining Ohmic contacts is difficult, especially for CdTe, because of the inherently low p-type doping level. Therefore, increasing the p-type doping level is important. Growth of CIGSS film must be controlled carefully as it transitions from Cu-rich to In-rich composition. Other issues for CIGSS cells are minimizing indium consumption, and increasing process throughput of selenization/sulfurization and transparent conducting oxide deposition. Development of all-dry processing for CdS deposition would be beneficial for both cells. This paper discusses basic devices and related issues. (c) 2005 American Vacuum Society.