Vapor induced Recrystallization of Methylammonium Tin Iodide Perovskite for Enhanced Stability

There is great interest in lead-free alternatives to hybrid organometallic lead halide perovskite. Unfortunately, methylammonium tin iodide (MASnI₃) is not stable in ambient due to prompt oxidation of Sn⁺² to Sn⁺⁴. The rate of degradation depends on morphology of the film. In this work, we demonstrate a post-deposition treatment that improves the grain size of MASnI₃ films from 100-150 nm to 1-2 microns, one of the highest numbers ever reported for this material. The films are highly crystalline, and show extended near infrared absorption showing suppressed tin oxidation and improved stability in ambient.