Heteroepitaxial Growth to Construct Hexagonal/Hexagonal β‐NaYF<sub>4</sub>:Yb,Tm/Cs<sub>4</sub>PbBr<sub>6</sub> Multi‐Code Emitting Core/Shell Nanocrystals
Rui Gao, Wanqing Xu, Zhiqing Wang, Fen Li, Yueli Liu, Guogang Li, Keqiang Chen
Abstract
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‐NaYF 4 and hexagonal Cs 4 PbBr 6 are filtrated to construct the UCNP/MHP heterostructural luminescent material. The similarity in their crystal structures facilitate the heteroepitaxial growth of Cs 4 PbBr 6 on the surface of β‐NaYF 4 NPs, leading to the formation of high‐quality β‐NaYF 4 :Yb,Tm/Cs 4 PbBr 6 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 Tm 3+ to Cs 4 PbBr 6 . It is noteworthy that the FRET efficiency of β‐NaYF 4 :Yb,Tm/Cs 4 PbBr 6 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 Cs 4 PbBr 6 . 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.