Ultrasensitive and Fast All‐Inorganic Perovskite‐Based Photodetector via Fast Carrier Diffusion

Low trap‐state density, high carrier mobility, and efficient charge carrier collection are key parameters for photodetectors with high sensitivity and fast response time. This study demonstrates a simple solution growth method to prepare CsPbBr 3 microcrystals (MCs) with low trap‐state density. Time‐dependent photoluminescence study with one‐photon excitation (OPE) and two‐photon excitation (TPE) indicates that CsPbBr 3 MCs exhibit fast carrier diffusion with carrier mobility over 100 cm 2 V −1 S −1 . Furthermore, CsPbBr 3 MC‐based photodetectors with high charge carriers' collection efficiency are fabricated. Such photodetectors show ultrahigh responsivity ( R ) up to 6 × 10 4 A W −1 with OPE and high R up to 6 A W −1 with TPE. The R for OPE is over one order of magnitude higher (the R for TPE is three orders of magnitude higher) than that of previously reported all‐inorganic perovskite‐based photodetectors. Moreover, the photodetectors exhibit fast response time of ≈1 ms, which corresponds to a gain ≈10 5 and a gain‐ bandwidth product of 10 8 Hz for OPE (a gain ≈10 3 and a gain‐bandwidth product of 10 6 Hz for TPE).