Chemical bath deposition of Cu₂O quantum dots onto ZnO nanorod arrays for application in photovoltaic devices

Cu₂O quantum dots (QDs) decorated ZnO nanorod arrays (ZNAs) were fabricated using a facile hydrothermal method followed by a chemical bath deposition (CBD) process. The surface morphology, crystal structure and photovoltaic behaviors of the heterostructure films were investigated. The results indicate that the Cu₂O QDs decorated ZNAs can be used as a good light absorber improving the visible spectral absorption. In addition, the photo-induced electrons can easily transfer to ZnO, leading to an increase in the photovoltaic performance. When the number of CBD cycles was 10, an optimal photovoltaic performance could be obtained under simulated sunlight illumination (AM 1.5G, 100 mW cm^-2) with a photocurrent of 3.21 mA cm^-2, an open circuit photovoltage of 0.65 V and a conversion efficiency of 1.17%. Moreover, for improving the photovoltaic stability, a protective layer was prepared on the Cu₂O QDs by a simple process of heat treatment in ambient air at 100°C for 2 h. The results demonstrate that the passive CuO layer could be an effective protective layer to increase the photovoltaic stability.