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

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 CsSnBr3 films with controlled GBs and surfaces are prepared successfully on glass by a solid-source chemical vapor deposition method. The grain size of CsSnBr3 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 CsSnBr3 film. Furthermore, the photodetector based on CsSnBr3 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.