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 CsPbBr₃ microcrystals (MCs) with low trap-state density. Time-dependent photoluminescence study with one-photon excitation (OPE) and two-photon excitation (TPE) indicates that CsPbBr₃ MCs exhibit fast carrier diffusion with carrier mobility over 100 cm² V^-1 S^-1. Furthermore, CsPbBr₃ MC-based photodetectors with high charge carriers' collection efficiency are fabricated. Such photodetectors show ultrahigh responsivity (R) up to 6 × 10⁴ 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 ≈10⁵ and a gain- bandwidth product of 10⁸ Hz for OPE (a gain ≈10³ and a gain-bandwidth product of 10⁶ Hz for TPE).