Synthesis of stable and phase-adjustable CsPbBr₃@Cs₄PbBr₆ nanocrystals via novel anion-cation reactions

All-inorganic cesium lead halide perovskites have emerged as promising semiconductor materials due to their preeminent performance in lighting, display, light detecting, and laser fields. However, the applications of lead halide perovskites are limited by the dissatisfactory stability owing to their fragile ionic crystal characteristics and highly dynamic surface-coordinated states. The in situ diphase structure passivation possessing the same chemical constituents (such as passivating CsPbBr₃ with Cs₄PbBr₆) has been proven to be an effective way to improve the stabilities and simultaneously maintain the highly efficient luminescence properties. Herein, for the first time, we report a novel anion-cation reaction method to synthesize the lead halide perovskite NCs with diphase CsPbBr₃@Cs₄PbBr₆ structure. Moreover, we have found that the phase transformation between CsPbBr₃ and Cs₄PbBr₆ is temperature dependent. Thus, we could control the relative composition of the diphase CsPbBr₃@Cs₄PbBr₆ composite by adjusting the temperature. The optimized CsPbBr₃@Cs₄PbBr₆ composite NCs achieve highly light emissive performance and stabilities against atmosphere, moisture and heating. Furthermore, we could obtain 135% of the NTSC color gamut through anion exchange. These highly emissive composite NCs with improved stabilities exhibit great potential in future optoelectronic fields.