Heteroepitaxial Growth to Construct Hexagonal/Hexagonal β‐NaYF₄:Yb,Tm/Cs₄PbBr₆ Multi‐Code Emitting Core/Shell Nanocrystals

Abstract

Synthesis of upconversion nanoparticles (UCNPs)‐metal halide perovskites (MHPs) heterostructure is garnered immense attentions due to their unparalleled photophysical properties. However, the obvious difference in their structural forms makes it a huge challenge. Herein, hexagonal β‐NaYF₄ and hexagonal Cs₄PbBr₆ are filtrated to construct the UCNP/MHP heterostructural luminescent material. The similarity in their crystal structures facilitate the heteroepitaxial growth of Cs₄PbBr₆ on the surface of β‐NaYF₄ NPs, leading to the formation of high‐quality β‐NaYF₄:Yb,Tm/Cs₄PbBr₆ core/shell nanocrystals (NCs). Interestingly, this heterostructure endows the core/shell NCs with typically narrow‐band green emission centered at 524 nm under 980 nm excitation, which should be attributed to the Förster resonance energy transfer (FRET) from Tm³⁺ to Cs₄PbBr₆. It is noteworthy that the FRET efficiency of β‐NaYF₄:Yb,Tm/Cs₄PbBr₆ core/shell NCs (58.33%) is much higher than that of the physically mixed sample (1.84%). In addition, the reduced defect density, lattice anchoring effect, as well as diluted ionic bonding proportion induced by the core/shell structure further increase the excellent water‐resistance and thermal cycling stability of Cs₄PbBr₆. These findings open up a new way to construct UCNP/MHP heterostructure with better multi‐code luminescence performance and stability and promote its wide optoelectronic applications.