CuIn(Ga)Se2 Solar Cell Fabricated By All Wet-Processes

Abstract

CuIn(Ga)Se2, I-III-IV chalcopyrite compound semiconductors, are attractive for thin film solar cells. Recently, energy conversion efficiency of CuIn(Ga)Se2 solar cells has been achieved over 20% based on vacuum process. To reduce fabrication cost, many efforts have been focused on non-vacuum process, and in this study we tried to fabricate the cells by almost all wet-processes; CuIn(Ga)Se2 absorption layers and In2S3 buffer layers were electrochemically deposited, and ZnO window layers were formed by solution based chemical methods. The deposited CuIn(Ga)Se2 absorption layers were heat-treated to improve crystallinity; however, due to surface cracks formed during heat-treatment, it was hard to adopt electrochemical method to form the absorption layers. Authors solved the problem to compensate the cracks by two-step electrodeposition process. Cd-based thin films had been used as buffer layers for a while, but nowadays many studies reported Cd-free buffer layers for CuIn(Ga)Se2 solar cells due to environmental destruction by toxicity of Cd. Therefore, we used In2S3 buffer layers forming by electrochemical method instead of Cd-bsed thin films. ZnO window layers were then deposited by solution based process in compact wire forms. We will discuss in this presentation about microstructures, chemical compositions, and light absorption abilities of each layer. And solar cell efficiency will also be presented.