Stability enhancement of lead-free CsSnI3 perovskite photodetector with reductive ascorbic acid additive

Lead-free tin-based perovskites have attracted widespread research interest due to their nontoxicity and potential commercialization. However, their practical application is limited by high density of intrinsic defects and easy oxidation of Sn2+ in ambient environment. To address these issues, we demonstrate an environment-friendly stable broadband photodetector based on CsSnI3 perovskite with conventional SnF2 and reducing agent ascorbic acid additive. Through optimizing the concentration of ascorbic acid, the optimal device reveals high responsivity (0.257AW(-1)), fast response speed (0.35/1.6 ms), and excellent stability. The properties are comparable to most previously reported lead-free perovskite photodetectors. The enhanced performance is mainly due to the fact that ascorbic acid promotes the crystal growth, suppresses the formation of Sn4+, and makes it have good semiconductivity rather than metallicity.