Toward High-Efficiency Cu(In,Ga)(S,Se)₂ Solar Cells by a Simultaneous Selenization and Sulfurization Rapid Thermal Process

Abstract

The open-circuit voltage (Voc) of copper indium gallium selenium (CIGSe) thin-film solar cells fabricated by a rapid thermal selenization process using elemental Se is limited to 600 mV, posing great challenges to high-efficiency CIGSe solar cells. In this study, we propose an effective method to improve the Voc of chalcopyrite solar cells by a simultaneous rapid thermal selenization and sulfurization process (RTP) using a Se capping layer and diluted H2S gas simultaneously. The high-temperature process time in RTP can be minimized without extra sulfurization time. The Voc of the Cu(In,Ga)(S,Se)2 (CIGSSe) solar cells was improved significantly by optimizing the concentration of the H2S gas and the thickness of the Se capping layer. We have successfully achieved high-efficiency CIGSSe solar cells above 17% by the RTP process using an elemental Se source with the optimized H2S content of 5% and the Se capping layer thickness of 0.85 μm The significance of this work is reducing the duration of the high-temperature process to less than 5 min, without toxic and expensive H2Se, therefore exerting strong attraction for industrial CIGSSe photovoltaic applications.