Surface modification of $\beta$-CIGS film by $Na_2S$ post-deposition treatment and its effect on cell performance

Abstract

High-efficiency thin-film solar cells based on polycrystalline CIGS require the incorporation of typically 0.1 at. % of sodium into the CIGS absorber layers. It seems that Na atoms give positive impact on the electrical properties of CIGS absorbers. Delicate studies have generally reported that Na elements show beneficial for bulk quality improvement by passivation of defects and grain boundaries. In this study, we investigated the impact of $Na_2S$ post-deposition treatment on the $\beta$-CIGS and in order to furtherly improve the efficiency of $\beta$-CIGS and let the $Na_2S$ post-deposition treatment works better, GGI ratio and Se flux was optimized.