Influence of Preparation Conditions on the Properties of Cu2S Photocathodes

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%