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

Abstract

AbstractPhotodetectors 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 (C60) and zinc phthalocyanine (ZnPc) is in contact with the graphene layer, can be significantly increased by doping the C60 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 C60 layers, the increased bandwidth is attributed to the reduced electron lifetime in the C60 trap state by recombination with holes photogenerated in the ZnPc domains in the C60 layer.