Synthesis and photoelectrochemical properties of (Cu₂Sn) _xZn_3(1-x)S₃ nanocrystal 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 (Cu₂Sn)_xZn _3(1-x)S₃ (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. (Cu₂Sn)_0.75Zn_0.75S₃ (Cu ₂ZnSnS₄) has a pure kesterite structure, but an increase in the Zn content results in a kesterite-wurtzite polytypism. (Cu ₂Sn)_xZn_3(1-x)S₃ 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 (Cu₂Sn)_0.45Zn_1.65S₃ (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 ₂ZnSnS₄ photocathodes.