Photoinduced charge transfer in ZnO/Cu2O heterostructure films studied by surface photovoltage technique

ZnO/Cu2O heterostructure films were prepared by a two-step electrodeposition method in aqueous solution on fluorine-doped tin oxide (FTO) substrates. Scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and UV-vis transmission measurements were utilized to characterize the films. Surface photovoltage (SPV) technique was used to investigate the process of photoinduced charge transfer. The results show that there is an electric field located at the interface between ZnO and Cu2O film and the photoinduced electrons in Cu2O film inject into ZnO under the effect of interfacial electric field with visible light irradiation. While under ultraviolet light illumination, the photoinduced electrons in Cu2O film accumulate at the surface of Cu2O film instead of injecting into ZnO under the action of surface built-in electric field of Cu2O film. The work function measurements confirm that the direction of interfacial electric field is from ZnO to Cu2O. These results are help to future design of high performance heterostructure photovoltaic devices.