A polyvinylpyrrolidone (PVP) thin film (9 nm) prepared on the top of Al-doped ZnO (AZO) electron transport layer by spin-coating, was developed as an interface modifier in inverted polymer solar cells (IPSCs). The PVP with excellent alcohol solubility provided a strong adhesion and wettability, leading to an improved interface quality between the AZO and active layer. Combined with a reduced work function of the AZO layer, the resulting devices showed a significant increase in power conversion efficiency from 2.86% to 4.08%, benefiting from the dramatic enhancement in fill factor (35%). Due to the ease of use and remarkable boost in efficiency, our results indicated that PVP was a promising candidate for surface modification material in IPSCs. (C) 2014 Elsevier B.V. All rights reserved.