Optimization of CBD CdS process in high-efficiency Cu(In,Ga)Se2-based solar cells

Abstract We present an optimization of the CdS chemical bath deposition process as applied to high-efficiency Cu(In,Ga)Se2 photovoltaic thin-film absorber materials. Specifically, we investigated deposition time (thickness), bath temperature (65, 80 and 90°C) and a Cd2+ partial-electrolyte treatment of the chalcopyrite absorber prior to CdS deposition. We found that thinner CdS layers (grown on as-deposited absorbers) allowing more light to reach the junction are not necessarily conducive to higher short-circuit current density. Device performance was found to be dependent on the CdS layer thickness, but rather independent of the growth temperature. On the other hand, devices prepared from absorbers subjected to a Cd2+ partial electrolyte treatment show that the device performance dependence on CdS thickness is somewhat alleviated, and devices incorporating thinner CdS layers are possible without loss of parameters, such as open-circuit voltage and fill factor.