Tunable Grain Boundary of Lead‐Free All‐Inorganic Perovskite Films for Smart Photodetectors

Abstract The nonradiative recombination caused by the trap states at the grain boundaries (GBs) and surfaces directly limits the photoelectronic performance of lead‐free all‐inorganic perovskites films. In this work, the typical CsSnBr 3 films with controlled GBs and surfaces are prepared successfully on glass by a solid‐source chemical vapor deposition method. The grain size of CsSnBr 3 films increases with the increase of growth temperature, indicating the reduction of GBs. Time‐resolved photoluminescence spectra show that the lifetime of photogenerated carrier is longer in the large‐grain‐size CsSnBr 3 film. Furthermore, the photodetector based on CsSnBr 3 film with decreased GBs shows excellent performance with photocurrent up to 760 nA, responsivity up to 9200 mA W −1 , and fast response times of 5/12 ms under the illumination of 405 nm laser. Moreover, the photodetector is also fabricated on a flexible substrate, demonstrating a good bending stability. This work provides a guideline in the growth of high‐quality perovskites films with controlled GBs and surfaces for next‐generation high‐performance photoelectronic devices.