In-situ preparation of ZnO/Cu2−xS on AZO conductive substrate and applied as counter electrode for quantum dot sensitized solar cells

Abstract In this work, the ZnO/Cu2−xS composite material is prepared based on Al doped zinc oxide glass substrate and applied as counter electrode (CE) in quantum dot sensitized solar cell. The ZnO/Cu2−xS CEs with the different Cu/S ratios of Cu2−xS (2-x = 1.73–1.48) can be controlled by immersing Cu/ZnO in different concentrations of S2- solution. As a result, the solar cell fabricated by Cu1.62S/ZnO CE exhibits the best photoelectric conversion efficiency of 5.35% under 1 sun illumination, which is higher than that of Cu1.62S CE (4.22%). On the basis of the result of solid-state current density–voltage test and transient photovoltage measurements, the formation of p-n heterojunction and the improving electrocatalytic activity in composite CEs accounts for the enhanced photoelectric conversion efficiency. These results are coincide with the outcomes of the impedance analysis, Tafel polarization measurement and cyclic voltammetry test for the symmetrical cell. Consequentially, the ZnO/Cu2−xS composite counter electrode is a promising material and the applications in solar cells.