In-situ growth all-inorganic bismuth-based perovskite single crystal hexagonal sheets for planar photodetector

Single crystal thin films can achieve the balance between thickness and mobility, which is widely used in the field of optoelectronic devices. Herein, lead-free perovskite Cs3Bi2I9 single crystal hexagonal sheets with preferred orientation along (0 0 2) were prepared by solution method. The Bi element is positively trivalent without oxidation in the single crystal hexagonal sheets. The growth processes of Cs3Bi2I9 crystal including nucleation and crystal growth are revealed by in-situ optical and structural observation. The Cs3Bi2I9 single crystal hexagonal sheets demonstrate excellent stability without encapsulation during long time exposure to the air. Obvious fluorescence quenching effect observed by steady-state and time-resolved photoluminescence measurement indicates charge transfer from Cs3Bi2I9 to ITO electrodes. Planar photodetectors based on Cs3Bi2I9 exhibit good photosensitive property, reproducibility and stability during multiple switching cycles. This work is conducive to lead-free perovskite regulation and further applications in photoelectronic devices.