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High-quality backlit display puts forward urgent demand for colorconverting materials. Recently, metal halide perovskites (MHPs) with full spectral tunability, high photoluminescence quantum yields (PLQYs), and high color purity have found potential application in wide-color-gamut display. Regrettably, naked MHPs suffer from long-term instable issue and cannot pass harsh stability tests. Herein, amorphous-glass-protected green/ red CsPbX 3 quantum dots (QDs) are prepared by elaborately optimizing glass structure, perovskite concentration, and in situ crystallization. PLQYs of green CsPbBr 3 @glass and red CsPbBr 1.5 I 1.5 @glass reach 94% and 78%, respectively, which are the highest ones of CsPbX 3 @glass composites reported so far and comparable to colloidal counterparts. Benefited from complete isolation of QDs from external environment by glass network, CsPbX 3 @glass can endure harsh commercial standard aging tests of 85 °C/85%RH and blue-light-irradiation, which are applied to construct white light-emitting diodes (wLEDs) with high external quantum efficiency of 13.8% and ultra-high luminance of 500 000 cd m −2 . Accordingly, the perovskite wLED arrays-based backlit unit and a prototype display device are designed for the first time, showing more vivid and wide-color-gamut feature benefited from narrowband emissions of CsPbX 3 QDs. This work highlights practical application of CsPbX 3 @glass composite as an efficient and stable light color converter in backlit display.

Perovskite nanocrystals (PNCs) are promising candidates for solar‐to‐fuel conversions yet exhibit low photocatalytic activities mainly due to serious recombination of photogenerated charge carriers. Constructing heterojunction is regarded as an effective method to promote the separation of charge carriers in PNCs. However, the low interfacial quality and non‐directional charge transfer in heterojunction lead to low charge transfer efficiency. Herein, a CsPbBr3–CdZnS heterojunction is designed and prepared via an in situ hot‐injection method for photocatalytic CO2 reduction. It is found that the high‐quality interface in heterojunction and anisotropic charge transfer of CdZnS nanorods (NRs) enable efficient spatial separation of charge carriers in CsPbBr3–CdZnS heterojunction. The CsPbBr3–CdZnS heterojunction achieves a higher CO yield (55.8 µmol g−1 h−1) than that of the pristine CsPbBr3 NCs (13.9 µmol g−1 h−1). Furthermore, spectroscopic experiments and density functional theory (DFT) simulations further confirm that the suppressed recombination of charge carriers and lowered energy barrier for CO2 reduction contribute to the improved photocatalytic activity of the CsPbBr3–CdZnS heterojunction. This work demonstrates a valid method to construct high‐quality heterojunction with directional charge transfer for photocatalytic CO2 reduction. This study is expected to pave a new avenue to design perovskite–chalcogenide heterojunction.

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