Synthesis and Photoelectrochemical Properties of (Cu₂Sn)xZn3(1–x)S₃Nanocrystal Films

This work provides new routes for developing efficient photoelectrodes for photoelectrochemical (PEC) water splitting using a low-cost electrophoretic film preparation method. A series of (Cu 2 Sn) x Zn 3(1– x ) S 3 (0 ≤ x ≤ 0.75) quaternary nanocrystals (NCs) with tunable optical band gaps are synthesized. Morphologies including particles, rods, and wires are obtained by tuning the composition of the NCs. (Cu 2 Sn) 0.75 Zn 0.75 S 3 (Cu 2 ZnSnS 4 ) has a pure kesterite structure, but an increase in the Zn content results in a kesterite–wurtzite polytypism. (Cu 2 Sn) x Zn 3(1– x ) S 3 films are fabricated from their colloidal solutions via electrophoretic deposition, and the PEC properties of these films with p-type character have been examined under water-splitting conditions. It is shown that the photocurrent varies as a function of film thickness as well as chemical composition. The produced (Cu 2 Sn) 0.45 Zn 1.65 S 3 ( x = 0.45) film has the highest photocurrent, and the incident photon to current conversion efficiency is improved compared with previously reported results of Cu 2 ZnSnS 4 photocathodes.