Stable and Bright CsPbX Nanocrystals in Metal-Organic Frameworks for White Light-Emitting Diodes.

The stability of metal halide perovskite (CsPbX, X = Cl, Br, and I) nanocrystals (NCs) is crucial for their practical applications. In this paper, perovskite NCs were synthesized in situ in lead-based metal-organic frameworks (Pb-MOFs: [Pb(1,3,5-HBTC)(HO)]·HO), and we obtained stable and bright luminescence composites with different colors. Namely, CsPbBr@Pb-MOF composites were created by the in situ growth of CsPbBr crystals (NCs) on Pb-MOF, which had high ion resistance, bright photoluminescence (PL), and excellent stability. The composites still had bright luminescence after 11 months of storage. The PL intensity of green-emitting CsPbBr@Pb-MOF composites was increased compared with as-prepared CsPbBr NCs. Bright and stable blue- and red-emitting CsPbX@Pb-MOF composites were obtained by adjusting the amount of PbX (X = Cl, Br, and I) in the synthesis process. These CsPbX NCs were homogeneously distributed in Pb-MOF substrates. The growth of CsPbX NCs in Pb-MOFs prevented NC aggregation and decreased surface defects against nonradiative recombination during emitting. Thus, the PL lifetime and stability were improved. Furthermore, white light-emission diodes were prepared using three color CsPbX@Pb-MOF composites with Commission Internationale de I'Eclairage color coordinates of (0.296, 0.316). This result provided an efficient way to overcome the limitation of chemical solution synthesis and improve the stability of CsPbX NCs.