Cu2O and CuO provide a unique possibility to tune the band gap into the middle of the efficiency maximum for photoelectrochemical (PEC) and solar cell applications. Photo active materials containing Cu2O, CuO and Cu2O/CuO have been prepared with high quality and stability in various compositions by an economic, simple and reliable electrodeposition (ED) method. These materials based on copper oxide have been characterized and compared using XRD, SEM, EDX, UV-Vis, PL, FTIR, Raman spectroscopy and electrochemical techniques. Based on the electrochemical production conditions; phase changes of photoactive materials and, at which conditions which phase or phases are present, were evaluated in detail. It was carried out that a full phase change from single-phase Cu2O to single-phase CuO. The crystal dimensions expand as the cube-shaped Cu2O transforms into CuO, crystal surface areas increase, crystal shapes change and turn gradually into flower-shaped crystals. Here, the band gap of copper oxide material can be altered within a broad scale by adjusting the element ratios. The semiconductors have been found to have direct band gap that is more preferred for solar energy applications. PEC performances of the copper oxide electrodes containing a different phase structure were determined, and the changes of PEC activities were examined comparatively. Copper oxide semiconductors have p-type conductivity and they act as photocathodes. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.