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

Tin-basedperovskites comprise one of the preferred nontoxic alternativesto Pb-based perovskites due to their desirable optoelectronic properties.However, there remains a crucial stability problem due to the propertyof Sn2+ oxidation. In this study, we reported stable tin-basedperovskite nanocrystals (NCs) using stannous acetate as the Sn2+ source because of its stronger Sn-O bonding. To preventthe oxidation of Sn2+, a thin layer of CsBr coverage wasformed 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 halfof the initial value is & SIM;1287 h under ambient conditions and & SIM;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 emittinglayer exhibit a maximum luminescence of 16 cd/m(2) and anexternal 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 provideda new way to obtain stable Sn-based perovskite NCs and exhibited theirpotential for application in white light-emitting diodes (LEDs).