Highly Ambient Stable CsSnBr₃ Perovskite via a New Facile Room-Temperature "Coprecipitation" Strategy

Tin-based perovskites are becoming promising alternatives to lead-based perovskites with eco-friendly merit and tantalizing photophysical properties. Unfortunately, the lack of facile, low-cost synthesis approaches associated with extremely poor stability greatly restrict their practical applications. Herein, a facile room-temperature "coprecipitation" method utilizing ethanol (EtOH) solvent and salicylic acid (SA) additive is proposed for synthesizing highly stable cubic phase CsSnBr₃ perovskite. Experimental results show that ethanol solvent and SA additive can not only effectively prevent the oxidation of Sn²⁺ during the synthesis processes but also stabilize the as-synthesized CsSnBr₃ perovskite. These are mainly ascribed to the protection effect of ethanol and SA, which are attached on the surface of CsSnBr₃ perovskite by coordinating with Br^- and Sn²⁺ ions, respectively. As a result, CsSnBr₃ perovskite can be obtained in open air and exhibits exceptional oxygen resistibility under moist air conditions (temperature: 24.2-25.8 °C; relative humidity: 63-78%). Absorption remains unchanged and photoluminescence (PL) intensity is vastly maintained (∼69%) after storage for 10 days, better than bulk CsSnBr₃ perovskite film synthesized by spin-coating method whose PL intensity is decreased to 43% after storage for 12 h. This work represents a step toward stable tin-based perovskite by a facile and low-cost strategy.