A Cu2O/ZnO nanowires solar cell has a theoretical maximum power conversion efficiency (PCE) of approximately 20%; however, the currently reported PCE is significantly lower due to its low photovoltage (V-oc). Herein we report an approach by using self-assembled polymer functionalization of the interface of Cu2O/ZnO nanowires heterojunction to boost the photovoltage for a greatly improved PCE, which is very likely to be resulted by a dipole moment of the polymer self-assembly layer. The polymer functionalized solar cells also show smaller reverse and leakage current, and higher built-in electric field. An enhancement mechanism of polymer assisted exciton separation and reduced recombination is proposed. This work is a simple and environmental friendly approach to improve the performance of the Cu2O/ZnO nanowires solar cells. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.