Stable Lead‐Free Tin Halide Perovskite with Operational Stability >1200 h by Suppressing Tin(II) Oxidation

Abstract Sn‐based perovskites are the most promising alternative materials for Pb‐based perovskites to address the toxicity problem of lead. However, the development of Sn II ‐based perovskites has been hindered by their extreme instability. Here, we synthesized efficient and stable lead‐free Cs 4 SnBr 6 perovskite by using SnF 2 as tin source instead of easily oxidized SnBr 2 . The SnF 2 configures a fluorine‐rich environment, which can not only suppress the oxidation of Sn 2+ in the synthesis, but also construct chemically stable Sn−F coordination to hinder the electron transfer from Sn 2+ to oxygen within the long‐term operation process. The SnF 2 ‐derived Cs 4 SnBr 6 perovskite shows a high photoluminescence quantum yield of 62.8 %, and excellent stability against oxygen, moisture, and light radiation for 1200 h, representing one of the most stable lead‐free perovskites. The results pave a new pathway to enhance the optical properties and stability of lead‐free perovskite for high‐performance light emitters.