<i>In Situ</i> Phase-Transition Crystallization of All-Inorganic Water-Resistant Exciton-Radiative Heteroepitaxial CsPbBr₃–CsPb₂Br₅ Core–Shell Perovskite Nanocrystals

Abstract

The instability of the metal halide perovskites upon exposure to moisture or heat strongly hampers their applications in optoelectronic devices. Here, we report the large-yield synthesis of highly water-resistant total-inorganic green luminescent CsPbBr3/CsPb2Br5 core/shell heteronanocrystals (HNCs) by developing an in situ phase-transition approach. It is implemented via the water-driven phase transition of the original monoclinic CsPbBr3 nanocrystal and the resultant tetragonal CsPb2Br5 nanoshell has a small lattice mismatch with the CsPbBr3 core, which ensures formation of an epitaxial interface for the synthesised CsPbBr3/CsPb2Br5 HNCs. These HNCs maintain nearly 100% of the original luminescence intensity after immersion in water for 11 months and the luminescence intensity drops only to 81.3% at 100 °C. Transient luminescence spectroscopy and density functional theory calculation reveal that there are double radiative recombination channels in the core CsPbBr3 nanocrystal, and the electron potential barrier provided by the CsPb2Br5 nanoshell significantly improves the exciton recombination rate. A prototype quasi-white light-emitting device based on these robust CsPbBr3/CsPb2Br5 HNCs is realized, showing their strong competence in solid-state lighting and wide color-gamut displays.