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

The open-circuit voltage (V-oc) 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 V-oc 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 V-oc 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 mu m 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.