Highly Stable CsPbBr₃ Perovskite Nanocrystals Encapsulated in Metal–Organic Frameworks for White Light-Emitting Diodes

Abstract

CsPbX3 (X = Cl, Br, I) perovskite nanocrystals (NCs) have shown great potential in numerous applications including wide color gamut display and lighting. Despite the wonderful luminescence properties, the inherent instability of these NCs hinders their use in practical situations. Herein, we report a facile aqueous-based, ligand-free method to synthesize highly stable CsPbX3 NCs using ZIF-62, a metal–organic framework, as an encapsulation matrix which effectively isolates CsPbX3 from the surrounding. We discovered that the slightly alkaline nature of ZIF-62 facilitates the reaction between water and PbBr2 to form PbBr(OH), which not only passivates the surface defects of the CsPbBr3 NCs but also prevents the perovskite from decomposing or oxidizing at high temperature. Sintering of ZIF-62 can therefore be performed in air at ∼300 °C to completely seal the perovskite within the insulating matrix, resulting in CsPbBr3/ZIF-62 composites exhibiting high stability against polar solvents, heat, light, and ambient humidity. Notably, the composite can maintain its bright luminescence without noticeable degradation in water for more than 2 months. The narrow-band emission and stability of these composites led to the demonstration of white light-emitting diodes with excellent color stability. Without the need for organic solvents during NC synthesis and noble gas ambient during sintering, the strategy proposed here can potentially facilitate the cost-effective, large-scale synthesis of highly stable perovskites which show great promise in commercial applications.

High Color Purity CsPbBr3 Nanocrystals Prepared by a Heterogeneous Reaction System

“…In general, CsPbBr 3 NCs with an ionic crystalline nature are susceptible to polar solvents, which deteriorates the optical performance of NCs. ,, To explore the influence of polar solvents on NCs, the stability of the prepared CsPbBr 3 NCs was tested suffering purification many times, and the spectra are shown in Figure a. The PLQY of colloidal ESA-CsPbBr 3 NC dispersion is still 86% after 13 cycles of purification with methyl acetate, and the PLQY of colloidal OBA-CsPbBr 3 NC dispersion is 87% after the same 5 cycles of purification.…”

Enhanced Photoelectric Properties of CsPbBr3 by SiO2 and TiO2 Bilayer Heterostructures

“…Due to the photophysical properties of CsPbX 3 (X = Cl, Br, I) NCs such as tunable PL spectra, narrow full width at half-maximum (fwhm), and high photoluminescence quantum yield (PLQY), they have made great progress in the fields of solar cells and light-emitting diodes (LED). − However, how to improve the stability of CsPbX 3 NCs remains a pressing issue. , The instability of CsPbX 3 NCs is mainly due to their ionic nature, which makes them very susceptible to irreversible degradation by reaction with water and oxygen . This is unfavorable for optoelectronic device applications.…”

Highly Luminescent and Stable Halide Perovskite Nanocrystals by Interfacial Defect Passivation and Amphiphilic Ligand Capping

“…Halide perovskites show great potential for light-emitting applications, − photovoltaics, and photocatalysis . Recently, water- and other polar solvent-based halide perovskites have been produced for real-world applications by coating their surface with polymers, inorganic layers, and silica. − Also, growing them inside porous silica and metal–organic frameworks (MOFs) or on the silica-based two-dimensional organic–inorganic hybrid nanoreactor with surface ligand engineering produces water-stable or amphiphilic perovskite nanocrystals (PNCs) . These coatings and matrices act as barriers for water molecules to reach the perovskite surface, protecting them from degradation.…”

“…These coatings and matrices act as barriers for water molecules to reach the perovskite surface, protecting them from degradation. Besides stability, the optical properties of polymer-coated, silica-coated, or matrix-embedded perovskites are improved through surface defect passivation. − Nevertheless, strain-induced lattice defects caused by the growth of thick shells around PNCs deteriorate their photoluminescence (PL) quantum yields (Φ) . Further, the encapsulation of PNCs inside polymers, silica, and MOF matrices can compromise their colloidal stability.…”