Bandwidth Enhancement of Graphene–Organic Hybrid Photoconductors by Accelerating Electron Transfer Processes at Graphene Interface

Photodetectors based on a heterojunction between graphene and photoactive layers have attractive features such as high responsivity and spectral sensitivity, but their narrow bandwidth originating from charge trapping is a major drawback. Here, it is demonstrated that the bandwidth of a graphene–organic hybrid photoconductor, where a planar bilayer of fullerene (C 60 ) and zinc phthalocyanine (ZnPc) is in contact with the graphene layer, can be significantly increased by doping the C 60 layer with ZnPc. The bandwidth, which increases with the doping concentration, is found to be more than two orders of magnitude higher at 40 vol% doping than that of the undoped device. Consequently, the 40%‐doped device has a fall time of the photocurrent transient of 19 μs, which is ≈300 times smaller than that of the undoped device (5.8 ms). Based on the model developed to analyze the electron transfer processes between the graphene and C 60 layers, the increased bandwidth is attributed to the reduced electron lifetime in the C 60 trap state by recombination with holes photogenerated in the ZnPc domains in the C 60  layer.