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Robust amorphous glass protected CsPbBr3 (CsPbBr3@glass) perovskite quantum dots (PeQDs) with ultra‐pure green emission and superior long‐term stability are highly desirable for developing wide‐color‐gamut liquid crystal displays. However, most of the reported CsPbBr3@glass nanocomposites are subject to low external quantum efficiency (EQE). This work demonstrates that ZrO2 additive has an "accumulation" effect on the borosilicate glass network structure to promote in situ nucleation/growth of PeQDs inside glass rather than self‐crystallization. This effect is beneficial in reducing surface defects, improving the quality of PeQDs, and thus boosting radiative recombination of excitons. As a consequence, the as‐prepared CsPbBr3@glass shows a record EQE of up to 75% and can pass the accelerated aging tests at 85 °C/85% RH for 1000 h and blue light irradiation over 2000 h. Finally, a prototype display using CsPbBr3@glass‐based straight‐down backlit unit is designed and gains more favorable responses in blind selection tests for its high brightness of 2647 cd m−2 and high color purity of 88%. The findings will pave the way for realizing the commercial application of CsPbBr3@glass nanocomposite in PeQDs‐converted backlit display. [ABSTRACT FROM AUTHOR]

Exploring new optical thermometric materials is important to realize highly accurate temperature detecting. Herein, Yb/Er activators are successfully doped into Cs 2 Ag(In/Bi)Cl 6 lead-free double perovskite (DP) semiconductor, providing dual-modal photoluminescence originated from self-trapped exciton recombination and 4f-4f transitions of Yb/Er dopants as well as Er3+ upconversion emissions. Remarkably different temperature-dependent emissive behaviors from DP host and Yb/Er activators are experimentally demonstrated, which enables to design novel fluorescence intensity ratio (FIR) between DP and Yb/Er based thermometric technology. In addition, upconversion FIR-based temperature sensing via thermal population between the 2H 11/2 level and 4S 3/2 one of Er3+ dopants in DP host is also realized. It is believed that the present Yb/Er: Cs 2 Ag(In/Bi)Cl 6 DP with excellent long-term stability and dual-functional temperature detecting is a suitable candidate as the self-calibrated optical thermometric material. The combination of the exciton recombination of Cs 2 AgInCl 6 lead-free double perovskite with Ln3+ (Ln = Yb, Er) dopants induces dual-modal light-emitting channel to produce a novel thermometric material. [Display omitted] • Yb/Er: Cs 2 Ag(In/Bi)Cl 6 lead-free double perovskite is successfully prepared. • The product exhibits both self-trapped exciton recombination and Ln3+: 4f-4f emissions. • Different temperature-dependent emissive behaviors from host and Ln3+ activators are demonstrated. • A novel DP/Ln3+ fluorescence intensity ratio thermometric channel is developed. • The product is a promising candidate for dual-modal optical temperature sensing. [ABSTRACT FROM AUTHOR]