Superstable Cs x SnBr x +2 @CsBr Nanocrystals with Over 1200 h of Half-Value PLQY in Air.

Tin-based perovskites comprise one of the preferred nontoxic alternatives to Pb-based perovskites due to their desirable optoelectronic properties. However, there remains a crucial stability problem due to the property of Sn 2+ oxidation. In this study, we reported stable tin-based perovskite nanocrystals (NCs) using stannous acetate as the Sn 2+ source because of its stronger Sn-O bonding. To prevent the oxidation of Sn 2+ , a thin layer of CsBr coverage was formed in situ; tin-based perovskite NCs, Cs x SnBr x +2 @CsBr (1 < x < 4), show a high photoluminescence quantum yield (PLQY) of 78.2% and high stability. The measured lifetime of PLQY decrease to half of the initial value is ∼1287 h under ambient conditions and ∼2200 h under a nitrogen atmosphere, respectively. Furthermore, the as-fabricated light-emitting diodes based on Cs x SnBr x +2 @CsBr NCs as the emitting layer exhibit a maximum luminescence of 16 cd/m 2 and an external quantum efficiency of 0.035% with peaks at 451 and 615 nm, corresponding to the emissions of CsBr and Cs x SnBr x +2 , respectively. This work provided a new way to obtain stable Sn-based perovskite NCs and exhibited their potential for application in white light-emitting diodes (LEDs).