Ultrastable and high colour rendering index WLEDs based on CsPbBrI2 nanocrystals prepared by a two-step facile encapsulation method

Abstract

Lead halide perovskite CsPbX₃ (X = Cl, Br, and I) nanocrystals (NCs) are widely used in the newest generation of lighting display equipment because of their excellent optical properties. However, their poor stability remains an urgent issue to overcome. Encapsulation has become a significant and effective strategy to promote the stability of perovskite NCs, particularly by the package coating of polymer and porous materials. Herein, a simple two-step encapsulation strategy is adopted to fabricate CsPbBrI₂@zeolite/PMMA composite films to replace the previous preparation methods of perovskite films. A highly efficient and stable red-emitting material with great colour purity and excellent PLQY of ∼53.9% is manufactured by this simple and effective packaging method. Furthermore, because of the first-encapsulation with zeolite, the CsPbBrI₂@zeoite/PMMA composite films not only reduced the agglomeration of NCs but also obtained better optical performance and environmental stability compared to that of pure CsPbBrI₂/PMMA. Ultimately, WLEDs constructed by the red-emitting CsPbBrI₂@zeolite/PMMA composite material achieve an outstanding colour rendering index, luminous efficiency and correlated color temperature (CRI = 94.5, LE = 77.22 lm W⁻¹ and CCT = 5354 K), and realize tunable colour coordinates of (0.3359–0.32912, 0.3455–0.3336) in the white light area, implying that CsPbBrI₂@zeolite/PMMA is very promising for obtaining a high CRI of WLEDs instead of traditional phosphor. The facile two-step encapsulation method proposed in this study provides a prospect for obtaining high-quality perovskites.