In this work, pristine reduced graphene oxide (RGO) sheets are added in the nanoarchitectural TiO2 nanorod (NR)-ZnO nanoparticle (NP)/P3HT hybrid polymer solar cells. With the addition of RGOs, the enhancement of the charge separation and the decrease of the electron lifetime in the nanoarchitectural metal oxide/P3HT hybrid are determined by time-resolved photoluminescence (TRPL) and impedance spectroscopy, respectively. The photovoltaic performance of the hybrid solar cell is therefore optimized by an appropriate addition of RGOs in the active layer. Moreover, intensity modulation of photocurrent spectroscopy measurements indicate that the electron transport rates in the hybrid solar cells are improved as adding RGOs in the active layer. Energy matching among P3HT, RGOs, and ZnO NPs is demonstrated in the TiO2 NR-ZnO NP/RGO/P3HT hybrid solar cell. It is respectively confirmed by TRPL and Kelvin probe force microscopy measurements that electron transfers occur effectively from P3HT to RGOs and from RGOs to ZnO NPs in the active layer. The pristine RGOs are concluded to be an energy-matched auxiliary electron acceptor in the nanoarchitectural metal-oxide/P3HT hybrid solar cell. An efficiency of 3.79% is achieved in the RGO-incorporated nanoarchitectural metal oxide/P3HT hybrid solar cell fabricated free of interfacial modification using the 900 nm-thick TiO2 NR array. (C) 2015 Elsevier B.V. All rights reserved.