Highly Bright and Stable CsPbX3@Cs4PbX6 Hexagonal Nanoarchitectonics Created by Controlling Dissolution‐Recrystallization of CsPbX3 Nanomaterials

Abstract CsPbBr 3 @Cs 4 PbBr 6 hexagonal NCs with a bright photoluminescence (PL) peak of 456 nm are created through the dissolution‐recrystallization of CsPbBr 3 nanoplatelets. Small CsPbBr 3 nanocrystals are encapsulated in hexagonal Cs 4 PbBr 6 during recrystallization to form a core‐shell structure and keep high brightness and stability. The recrystallization kinetics is systematically investigated to explore the roles of methyl acetate, oleylamine, and n‐hexane. Result further indicates that core/shell NCs remained high PL under a variety of harsh conditions (e.g., light irradiation and heat treatment) because of Cs 4 PbX 6 shell and the controlling of recrystallization. Their initial PL intensity is remained after 4 months of storage under ambient conditions and continuous exposure to UV lamp for 180 min. The bright PL is also maintained even treatment at 120 °C. To indicate the universality of this synthesis method, CsPbX 3 @Cs 4 PbX 6 hexagonal NCs with different emission colors are fabricated by changing temperature, solvent viscosity, and precursors (e,g, oleylamine and halogens). These core‐shell samples reveal bright and stable green, orange, and red PL. Because of its high stability, the core/shell NCs are dispersed in flexible films to create diverse patterns. The films also exhibit high brightness and excellent stability. This strategy opens a novel avenue for the application of perovskite nanomaterials in the display field.