Highly Stable CsPbBr₃ Perovskite Nanocrystals\nEncapsulated in Metal–Organic Frameworks for White Light-Emitting\nDiodes

Abstract

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