Chemical bath deposited (CBD) ZnS buffer layer for CIGSS solar cells

Cadmium free buffer layers for Cu(In,Ga)S_xSe_2-x (CIGSS) thin film solar cells have been fabricated using a chemical bath deposition (CBD) technique. The purpose of this work was to replace the chemically deposited CdS buffer layer with an alternative non-cadmium buffer layer. In this study a major effort was made to improve quality of the ZnS buffer layers on 4cm² (2cm×2cm) CIGSS substrates. The use of CBD-ZnS layer, which is a higher band gap material than CBD-CdS, improved the quantum efficiency of the fabricated cells at short wavelengths, leading to a acceptable short circuit current (Jsc). The best cell yielded an active area efficiency of 13.3% on 0.42 cm² as measured by NREL.