Abstract: Cu₂S nanomaterials were prepared, and the influence of preparation conditions on the morphology and catalytic reduction of sodium polysulfide was investigated. The Cu₂S photocathode prepared under optimal conditions was used as a quantum-dot-sensitized solar cell. For preparation of the Cu₂S photocathodes, HCl pretreatment and reaction with sodium polysulfide were important processes. The Cu₂S photocathodes had petal-like structures composed of nano-plates. The Cu₂S photocathodes become rough and porous, which increased the surface area, as the HCl concentration increased and pretreatment time was prolonged. As a result, interfacial charge transfer resistance between the Cu₂S electrodes and polysulfide electrolyte decreased. Because the reaction between Cu and sodium polysulfide is very fast, the reaction time should be controlled. Otherwise, the Cu₂S film will fracture. For good catalytic performance of the Cu₂S photocathodes, the best preparation conditions were 30% HCl, pretreatment time for 40 min, and reaction with sodium polysulfide for 10 s. The quantum-dot-sensitized solar cell showed a high photoelectric conversion efficiency of 4.01%.

Key words: Cu₂S, Photocathode, Interfacial charge transfer resistance, Impedance, Quantum-dotsensitized solar cell