Improved hybrid solar cells consisting of vertical aligned cadmium sulfide (CdS) nanorod arrays and interpenetrating polythiophene (P3HT) have been fabricated via modification on CdS nanorod surface by using aromatic acid as surface ligands. Morphology of CdS/P3HT composite film with interface modification was studied by scanning electron microscopy. The interaction between ligand molecule and CdS nanorod surface was tentatively studied by absorption spectrum, fluorescence spectrum and X-ray photoelectron spectrum. The roles of surface ligands on the improvement of device performance were discussed further from the analysis of photoluminescence spectra, dipole effect and theoretical simulation of photovoltaic characteristics. (C) 2010 Elsevier B.V. All rights reserved.