Organolead trihalide perovskites (methyl ammonium lead halide, or CH3NH3PbX3, where X is a halogen) have become a hot topic in materials science for their light-collection properties useful for photodetectors. At present, the performance of photodetectors based on perovskite polycrystalline thin films has not achieved its potential; one of the main reasons is that the carrier transport at the interface is easily affected by grain boundaries and grain defects. Numerous research groups have tried to combine perovskite polycrystalline thin films with high-mobility 2D materials to improve device performance and have achieved some encouraging results, but the negative effects of perovskite polycrystalline grain boundaries still remain.
To solve this problem, a team led by Yu Weili from Changchun Institute of Optics, Fine Mechanics and Physics (CIOMP) of the Chinese Academy of Sciences (Beijing, China) and Chunlei Guo from the University of Rochester (Rochester, NY) synthesized low-surface-defect-density CH3NH3PbBr3 microplates using an inverse temperature crystallization approach, and prepared an effective vertical structure photodetector combining high-quality perovskite single crystals with monolayer graphene having high carrier mobility. The vertical photodetectors made with these microplates and monolayer graphene exhibit excellent light response, with high light responsivity (1017.1 A/W), high light detectivity (2.02 × 1013 Jones), and ultrahigh gain (2.37 × 103) under 532 nm laser irradiation at room temperature. The parameters are approximately one order of magnitude larger than that of similar photodetectors without monolayer graphene.
Carrier ultrafast kinetics studies have shown that the improvement in device performance is mainly due to the increased lifetime of perovskite carriers of high-quality perovskite crystals and the effective extraction and transport of free charge by graphene. The improved device performance for the perovskite/graphene photodetectors is believed to be closely related to the operational synergy of the two materials in carrier generation and transportation. Reference: Y. Zou et al., Small (2020); https://doi.org/10.1002/smll.202000733.
