We employ 3-PPA, BPA and APPA as self-assembled monolayers (SAMs), who owns the same phosphonic acid headgroup but different tail group, to modify the surface of ZnO nanorods. Their effects on the photovoltaic performance of quantum dots sensitized soar cells are systematically investigated. The results indicate that the deposition of SAMs not only passivates the surface defects of ZnO nanorods, but also tunes their surface work function to adjust the band alignment of solar cells. In particular, the 3-PPA modification exhibits the best passivation effect and makes the surface work function of ZnO decreases by 1.04 eV to realize a better band alignment due to its electron-withdrawing tailgroup, which results in an enhancement in photovoltaic conversion efficiency of solar cells. (C) 2015 Elsevier Ltd. All rights reserved.