Characterization of Cu-Based I-V-VI Thin Films Using Hybrid Inks

Abstract

Cu(In,Ga)Se2 (CIGS) and Cu2ZnSnSe4 (CZTSe) have been studied as the most promising materials in solar cell research and production area. Until now, CIGS solar cell has already reported over 21 % conversion efficiency. Despite the real progress of efficiency, however, CIGS and CZTS absorbers in photovoltaic cells have been challenged by many problems, such as elemental scarcity, toxicity and structural complexity. Especially, complex stoichiometry and high process temperature are important obstacles to overcome because the elemental ratio of absorbers is hard to control and the bottom-cell can be easily degraded for fabricating high efficient tandem solar cell while the top-cell process is carrying on. Recently, Cu-based I-V-Vl materials, especially Cu-Sb-S phases, have been highlighted because of their characters, such as a band gap and a high optical absorption co-efficient. In the Cu-Sb-S phases, there are four major phases (CuSbS2, Cu3SbS3, Cu3SbS4, Cu12Sb4S13) but most of research have reported only about synthesis and characterization of nanocrystals. In this study, thin films of Cu-Sb-S phases were formed using non-vacuum process which is cost-effective. To form thin films of Cu-Sb-S using a non-vacuum hybrid ink, Cu and Sb precursors were coated and sulfurized with a rapid thermal annealing (RTA) process. However, each optimum sulfurization condition is needed to obtain single phase thin films of each material. The fabricating thin films were analyzed and confirmed as target phases. The characteristics of each Cu-Sb-S absorber and photovoltaic performances of fabricated cells will be presented.