Synergistic Confinement and Passivation Effects Enable High PLQY and Ultrastable CsPbBr3 in Mg‐Silicalite‐1 for Backlight Displays

All inorganic perovskite quantum dots (PQDs) are emerging as highly promising luminescent nanomaterials in display field for their outstanding optical properties. However, it is still a great challenge to prepare CsPbBr3 PQDs that boast both superior photoluminescence quantum yield (PLQY) and ultrahigh stability. Herein, Mg‐doped silicalite‐1 (MS‐1) zeolite is employed as a matrix to develop a CsPbBr3@MS‐1 composite through a straightforward thermal diffusion strategy, achieving ultrahigh PLQY of 97.4% for bright green solid‐state fluorescence emission. The PLQY of CsPbBr3@MS‐1 composite remains over 90% even after 6 months in air. Additionally, the composite demonstrates outstanding luminescent stability against heat, ultraviolet (UV) irradiation, and erosion effects of both acidic and alkaline solutions. The synergistic protection from both the dense zeolite shell and the passivation by magnesium ions detached from the framework facilitates reduction of intrinsic bromine vacancies on the CsPbBr3 surface, thereby minimizing nonradiative recombination centers and resulting in ultrahigh stability and PLQY. A standard white light emitting diode (LED) with a maximum luminous efficiency of 63.12 lm W−1 and outstanding stability is constructed based on CsPbBr3@MS‐1 composite, commercial red phosphor, and a blue chip. This work introduces a novel approach to create high‐efficiency and ultrastable PQDs within zeolite matrix, offering broad applications in display technology.