TiO2 Nanocrystal/Perovskite Bilayer for High‐Performance Photodetectors

Owing to their attractive performance in photovoltaic devices, organolead halide perovskite materials have attracted enormous interest for photodetector applications. However, current perovskite‐based photodetectors mainly rely on high‐conductive 2D materials such as graphene or transition metal sulfides to transport photocarriers, which indeed significantly improve the photoresponsivity but seriously weaken other parameters such as on/off ratio or response speed. Achieving a high overall performance remains a challenge. Here, a solution‐processed TiO2 nanocrystal (NC) film is employed to transport photocarriers. The designed TiO2 NC/perovskite (CH3NH3PbI3) bilayer device exhibits satisfactory overall performance with on/off ratio of 4000, photodetectivity of 1.85 × 1012 Jones, and rise/decay time of 0.49/0.56 s. The device can also be integrated on flexible polyimide substrate. This work provides a strategy to realize high‐performance perovskite‐based photodetectors and clearly demonstrates their potential applications in future flexible optoelectronics. TiO2 nanocrystal (NC) film is used to construct a TiO2 NC/perovskite bilayer photodetector, which shows high overall performance with on/off ratio of 4000, detectivity of 1.85 × 1012 Jones, and rise/decay time of 0.49/0.56 s. The device is also fabricated on flexible polyimide substrate and displays comparable performance with a glass‐based one, indicating its great potential in future flexible optoelectronics.