A Dual Strategy to Prepare CsPbBr₃@glass with a High PLQY and Ultrastability: Combining Controllable Crystallization and Surface Modification

All‐inorganic perovskite quantum dots (PQDs) are widely applied in photoelectronics because of their high luminous efficiency. However, PQDs have poor stability, which hinders their practical applications. In this study, controllable crystallization of PQDs is achieved by adding Al 2 O 3 to alter the glass network. Next, Na 2 CO 3 (aq) washing‐heating treatment is used to improve the protective mechanism. Owing to this dual strategy, the prepared CsPbBr 3 @glass exhibits a high photoluminescence quantum yield (PLQY > 95%) and excellent stability. In a 1000 h accelerated aging experiment, the luminous intensity remains above 96% of the initial intensity. The luminescence intensity shows almost no change after soaking in water for 20 weeks. Finally, the CsPbBr 3 @CsPbBr 1 I 2 @PET light‐conversion film is prepared by the sandwich method. Its color gamut covers 138% of the NTSC 1953 and 102% of the Rec. 2020. This CsPbBr 3 @glass with a high PLQY and ultrastability will broaden the scope of perovskite materials in displays.