Microstructure, wettability and electrical properties of n-ZnO/ZnO-SL/p-Cu2O heterojunction

ZnO/ZnO-SL/Cu2O heterojunction was successfully fabricated on Cu foil by hydrothermal and sol–gel method. Crystalline phase, surface morphology and photoluminescence spectrum of the heterojunction were measured by X-ray diffraction, scanning electronic microscopy and fluorescence spectrometer, respectively. Contact angles of ZnO thin films were measured using a contact angle apparatus. The current–voltage characteristics of heterojunction in dark were investigated at room temperature. The results indicated that the heterojunction was composed of Cu2O phase and ZnO phase. The post-heat temperature of 250 °C was beneficial to preferred growth of ZnO thin film along the c-axis direction. The Sample 2 was composed of the uniform, compact and vertically aligned ZnO nanorods and has the most obvious hydrophobic-to-hydrophilic transition. The transport characteristics of the Sample 2 may be related to the space-charge-limited current in region II and a trapped-charge-limited current in region III.