Titanium oxide (TiOx) was introduced as an electron selective layer between the active layer and bottom electrode in inverted organic solar cells with graphene oxide (GO) an anode interfacial layer. The device with TiOx exhibited a significant enhancement in power conversion efficiency compared to that without TiOx which indicates that TiOx efficiently blocked holes at the active/bottom layer. This device exhibits good stability over 2160 h of storage with only 3.67% reduction in efficiency. The dependence of the device performances on TiOx film thickness was also investigated. (C) 2012 Elsevier B.V. All rights reserved.