Vapor-Phase Deposition of CsPbBr3 Shells on Iodide-Rich Perovskite Cores in SiO2 for Efficient and Robust Red Emission.

While high-temperature solid-phase confined synthesis has established itself as a viable approach for producing ultra-stable halide perovskite nanocrystals (NCs), the photoluminescence quantum yield (PLQY) of the resulting red-emitting NCs, whether pure-iodide or mixed-halide, remains unsatisfactory. In this work, we introduce a high-temperature vapor-phase deposition for the controlled synthesis of CsPbI3/CsPbBr3 and CsPb(Br/I)3/CsPbBr3 heterostructure NCs encapsulated within a robust SiO2 matrix. This method spatially separates the CsPbBr3 shell precursor from the preformed iodine-rich core in the vapor phase, effectively suppressing undesirable halide diffusion during high-temperature processing at 700°C. By leveraging the strong Br─Cs/Pb interactions, the CsPbBr3 vapor promotes preferential interfacial deposition on CsPbI3 or CsPb(Br/I)3 cores. The resulting NCs display highly efficient red emission, achieving a PLQY as high as 85%. Furthermore, benefiting from the dual protection of the SiO2 matrix and the heterostructure, these red-emitting materials exhibit outstanding environmental stability while retaining their high performance.