Three-dimensional (3D) heterojunctions consisting of Cu2O and ZnO nanorods were assembled via the electrochemical superfilling approach. This procedure included two electrochemical steps: the initial low-temperature nucleation of Cu2O on the surface of ZnO nanorods at high cathodic overpotential and the subsequent high-temperature growth at low cathodic overpotential. The structural morphologies, electrical properties and the interface features of the 3D heterojunction were characterized with SEM observation, I-V and Mott-Schottky testing and the impedance measurement. The bottom-up growth of Cu2O in ZnO nanorod arrays was realized. The filling depth was over 4.0 mu m. The dense structure had good electrical contact and large forward current, but the enlarged junction area and grain boundaries produced great interface state density, which contributed to the relative lower conversion efficiency of 0.08%. (C) 2012 Elsevier Ltd. All rights reserved.