▎ 摘　　要

We investigate organic bulk heterojunction (BHJ) devices that employ graphene nanosheets in the active layer. Solar cells based on P3HT:PCBM:graphene show device physics significantly different from traditional BHJs, and display a monotonic increase in performance with graphene concentration. The efficiency increases threefold upon addition of graphene due to the higher photocurrent. External quantum efficiency measurements demonstrate significant changes in morphology for devices with graphene. Incorporating such high aspect ratio fillers enables an alternate paradigm for polymer-based solar cells, with much higher concentrations of conjugated polymer, thereby enhancing the capture of solar energy. (c) 2013 Elsevier B.V. All rights reserved.