We demonstrate efficient hybrid inorganic/organic p-i-n photovoltaic (PV) devices with a p-type-doped hydrogenated amorphous silicon (a-Si:H), intrinsic a-Si:H, and an organic semiconductor, pentacene. The correlation between the electrical properties of the PV devices and the morphological properties of the pentacene films were investigated using absorption spectroscopy, X-ray diffraction, and scanning electron microscopy. The maximum power conversion efficiency can be increased by one order with respect to the devices using different thicknesses of a pentacene layer from 0.32% at 10 nm to above 3.0% at 30 nm. Photocarriers in PVs are suggested to be mainly generated in the intrinsic a-Si:H layer. The pentacene layer is used as the exciton-blocking and electron-transport layer. Thus, the structural quality of pentacene films plays an important role in PV performance. (C) 2011 Elsevier B.V. All rights reserved.