Optimizing chemical bath deposition of cadmium sulfide for CuInGaSe based semi-transparent photovoltaics

A novel application of thin-film photovoltaics is the Semi-Transparent Photovoltaics (STPV) for building integrated applications, where CuIn1−xGaxSe2 (CIGS) based solar cells can be a major candidate. To get the optimum efficiency for a given visible transparency, each layer in the thin-film stack needs to be optimized. In this paper, we optimize the cadmium sulfide (CdS) buffer layer for the CIGS based STPV using the chemical bath deposition technique. Several samples are deposited on clear glass and the highest visible transparency (71%) is found for the deposition time of 20 minutes, solution temperature of 80°C, stirring rate of 200 rpm and cadmium-sulfur reactant ratio of 1:10. The thickness measured from SEM micrograph is found to be 66 nm, which is the range of optimum thickness for this type of application.