Postsynthesis Phase Transformation for CsPbBr₃/Rb₄PbBr₆ Core/Shell Nanocrystals with Exceptional Photostability

Lead halide perovskite nanocrystals (NCs) as promising optoelectronic materials are intensively researched. However, instability is one of the biggest challenges needed to overcome before fulfill their practical applications. To improve their stability, we present a postsynthetic controlled phase transformation of CsPbBr₃ toward CsPbBr₃/Rb₄PbBr₆ core/shell structure triggered by rubidium oleate treatment. The resulting core/shell NCs show exceptional photostability both in solution and on-chip. The solution of CsPbBr₃/Rb₄PbBr₆ NCs can remain over 90% of the initial emission photoluminescence quantum yields after 42 h of intense light-emitting diodes illumination (450 nm, 175 mW/cm²), which is even better than the conventional CdSe/CdS quantum dots whose emission drop to 50% after 18 h under the same condition. We believe that the exceptional photostability should be resulted from the protection of the robust Rb₄PbBr₆ shell on CsPbBr₃ NCs.