An interface engineering process to deploy graphene film as the anode in poly(3-hexylthiophene-2,5-diyl):[ 6,6]-phenyl C61 butyric acid methyl ester (P3HT:PCBM)-based polymer solar cells is demonstrated. By modifying the interface between the graphene anode and the photoactive layer with MoO3 and poly(3,4-ethylenedioythiophene): poly(sty renesulfonate) (PEDOT:PSS), the power conversion efficiency of the solar cells reaches approximate to 83.3% of control devices that use an indium tin oxide (ITO) anode.