Metal sulfide precursor aqueous solutions for fabrication of Cu2ZnSn(S,Se)4 thin film solar cells

Aqueous solution deposition of metal chalcogenide semiconductor thin films is considered a green and low-cost approach. However, it is hard to find a general aqueous solution approach to deposit various kinds of high-quality metal sulfide thin films. Here, we describe a green and robust ammonium thioglycolate aqueous solution approach, and fifteen types of metal sulfide precursor solutions (metal = Cu, Zn, Sn, Ge, In, Sb, Mg, Cd, Mn, Bi, Fe, Ni, Li, Na, K) can be prepared using metal oxides or metal hydroxides as raw materials at room temperature under an air atmosphere. Moreover, elemental sulfur and selenium can also be highly dissolved. By this green route, high quality CZTS nanocrystal thin films can be deposited by directly coating the mixed Cu, Zn, and Sn precursor solutions without the need for complex nanocrystal synthesis. The remarkable power conversion efficiency of 6.62% was achieved, which is the highest value for aqueous solution deposited CZTSSe thin film solar cells.