Heterojunction devices were fabricated and composed of Al-doped ZnO films deposited by radio-frequency magnetron sputtering on Cu2O films with different orientation obtained by potentiostatic electrodeposition. Compared to the Al-doped ZnO/(200)-orientated Cu2O heterojunction, regardless of the intentional substrate heating during the deposition of Al-doped ZnO, the Al-doped ZnO/(111)-orientated Cu2O heterojunction has an epitaxy-like growth for Al-doped ZnO films due to a small lattice mismatch of about 7.1%. With the substrate heating, the resistance of the device increases, although the crystallinity of Al-doped ZnO films could be improved. The device composed of Al-doped ZnO/(111)-orientated Cu2O without substrate heating has the best photovoltaic characteristics and the highest conversion efficiency of 0.069% under the illumination condition of AM1.5 in this study. In addition, by modifying the thickness of the heterojunction, the best conversion efficiency of the Al-doped ZnO(200 nm)/(111)-orientated Cu2O (1 mu m) heterojunction could be promoted to 0.22% with a short-circuit current (J(SC)) of 4.3 mA/cm(2), an open-circuit voltage (V-OC) of 0.15 V, and a fill factor of 0.29. (C) 2008 The Electrochemical Society.