In recent years, organic photovoltaics (OPVs) as one of nextgeneration solar energy technologies have attracted intense interest since they are featured with low cost, light weight,flexibility and semi-transparency [1].At the early stage in the OPV field, fullerenes and their derivatives dominated electron acceptor materials due to their high electron affinity,high electron mobility and isotropic electron transporting ability, and fullerene-based devices yielded power conversion efficiencies (PCEs) up to ~12% [2].