Emerging lead-free all inorganic perovskite single crystals KBiX (X = Cl, Br) toward photodetector application.

Lead-free inorganic perovskites have attracted intensive attention in the field of photodetectors owing to their high stability, non-toxicity, and remarkable photoelectric characteristics. Herein, we designed and developed a series of thus-far unreported lead-free all inorganic perovskite single crystals, KBiX (X = Cl, Br). In particular, we resorted to cooling crystallization and intercalated K to inorganic Bi-Br and Bi-Cl frameworks as inorganic A-site cations, obtaining zero-dimensional (0D) KBiX (X = Cl, Br) perovskite single crystals, which display suitable bandgaps, excellent electron mobility and low trap-state density, as analysed by experimental characterization and density functional theory (DFT) calculations. Accordingly, the vertical structure KBiBr photodetector can achieve a fast ON/OFF switch under the irradiation of 395 nm light. When the light intensity is 5 mW cm and the voltage is 3 V, the responsivity is calculated to be 0.052 mA W. The above characteristics make KBiBr a promising material for fabricating ultraviolet photodetectors.