Efficient organic solar cells (OSCs) based on the blends of poly(3-hexylthiophene): fullerene derivative [6,6]-phenyl-C61 butyric acid methyl ester composites have been fabricated on fluorine-doped tin oxide coated glass substrates using the sputtered nitrogen doped amorphous chromium oxide (NACO) film as a hole-transporting layer (HTL). Optimized parameters for p-type NACO layer fabrication have been obtained through argon/oxygen/nitrogen flow ratio variations. Based on the HTL, the power conversion efficiency up to 3.17% has been achieved. With the help of X-ray photoelectron spectroscopy and Hall-effect measurements, we come to a conclusion that CrN in amorphous chromium oxide (ACO) film could prevent water dissociation and hydroxylation at defect sites on the ACO film surface, and reduce the electrical resistivity of films. The stability of NACO as HTL has been improved compared with that of ACO as HTL, which can improve the performance of OSC. (C) 2010 Elsevier B.V. All rights reserved.