Efficient organic solar cells (OSCs) based on regioregular of poly (3-hexylthiophene): fullerene derivative [6,6]-phenyl-C-61 butyric acid methyl ester composites have been fabricated on fluorine-doped tin oxide coated glass substrates by using a sputtered indium oxide film as a hole-transporting layer (HTL). Optimized parameters for p-type In2O3 layer fabrication have been obtained through In2O3 layer sputtering temperature modulation. Based on this HTL, photovoltaic devices have been fabricated, and a power conversion efficiency up to 1.32% has been achieved. With the help of X-ray photoelectron spectroscopy and Hall-effect measurements, we conclude that the formation of In(OH)(3)/InOOH on the surface of In2O3 film could increase the electrical resistivity of films and affect the performance of OSC further. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.