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).

CsPbBr₃ microcrystal (MC)-based photodetectors exhibit ultrahigh responsivity (R) up to 6 × 10⁴ A W⁻¹ with one-photon excitation and R = 6 A W⁻¹ with two-photon excitation. The photodetectors also exhibit fast response time of ≈1 ms. The sensitive and fast photoresponse is ascribed to the large absorption coefficient, low trap-state density, and high carrier mobility of CsPbBr₃ MCs.

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