Abstract: Well-defined cuprous oxide (Cu2O) thin film electrodes were electrodeposited on indium-doped tin oxide (ITO) substrates from a slightly acidic Cu(II) acetate solution. The morphologies of Cu2O film were tunable by altering the deposition potential, reaction time, solution temperature and the NaCl concentration. In particular, the Cu2O morphologies evolved from dendritic branching to cube-like with the increasing of the NaCl concentration. A growth mechanism was proposed according to the experimental results. In addition, a photocurrent of 0.06 mA cm(-2), an open-circuit photovoltage (V-oc) of 0.38 V, and a significant energy conversation efficiency of 0.01% were obtained under 100 mW cm(-2) UV-visible illumination of the dendritic Cu2O thin film.