Versatile and Low-Toxic Solution Approach to Binary, Ternary, and Quaternary Metal Sulfide Thin Films and Its Application in Cu₂ZnSn(S,Se)₄ Solar Cells

We developed a versatile and environmentally friendly solution approach for the fabrication of a variety of metal sulfide nanocrystal thin films. Metal oxides, metal hydroxides, metal chlorides, metal acetates, and metal acetylacetonates can be used as the starting materials and dissolved in thioglycolic acid and ethanolamine, forming many types of metal–organic precursor solutions. High quality CdS, SnS, CuInS 2, CuSbS 2, Cu 2 ZnSnS 4, Cu(In 0.7 Ga 0.3 )S 2, and luminescent Ag-doped Zn x Cd 1– x S nanocrystal thin films have been successfully prepared by spin-coating their corresponding metal precursor solutions. Cu 2 ZnSn(S,Se) 4 thin film solar cell with a power conversion efficiency of 6.83% has been realized by this versatile method.