Ionic liquid-assisted green solution approach for high-performance Cu2ZnSn(S,Se)4 thin film solar cells

In this research, a facile and environmentally friendly solution approach is developed to deposit Cu 2 ZnSn(S,Se) 4 thin films by addition of n -butylammonium butyrate ionic liquid . n -Butylammonium butyrate plays a critical role in solution deposition of Cu 2 ZnSnS 4 precursor thin film. We find that liquid n -butylammonium butyrate can dissolve a number of metal oxides , including Cu 2 O, ZnO, and SnO as well as various metal chlorides , metal nitrates and metal acetates. Smell-free Cu 2 ZnSnS 4 precursor solution is synthesized by dissolving Cu 2 O, ZnO, SnCl 2 and thiourea in an ethanol solution of n -butylammonium butyrate. Thermally degradable n -butylammonium butyrate can be completely removed by a low-temperature sintering process , forming high quality Cu 2 ZnSnS 4 nanoparticle thin film. A power conversion efficiency of 8.79% is obtained by this facile and green solution approach.