In recent years, all-inorganic metal lead halide cesium perovskites (CsPbX 3 , X = Cl, Br, and I) have shown excellent luminescence performance in the field of wide color gamut backlight displays. However, Pb 2+ in CsPbX 3 easily leaks because of the unstable structure of CsPbX 3 , which seriously threatens human health. However, Mn-based metal halides (MHs) have unique environmentally friendly characteristics. In this work, Zn 2+ -doped Cs 3 MnBr 5 MHs were successfully prepared, which exhibited highly efficient green emissions at 520−522 nm. Moreover, Cs 3 Mn x Zn (1−x) Br 5 shows excellent stability at room temperature (25 °C) compared with Cs 3 MnBr 5 . More excitingly, when Cs 3 Mn x Zn (1−x) Br 5 was encapsulated in a polystyrene (PS) polymer, Cs 3 Mn x Zn (1−x) Br 5 @PS showed better water, acid, daylight, and blue light stabilities. In addition, the backlight display device was designed based on different green−red ratios and thicknesses of Cs 3 Mn x Zn (1−x) Br 5 @K 2 SiF 6 :Mn 4+ @PS light conversion films, and the color gamut was over 109% of the NTSC 1953 standard, which is better than that of the reported WLED devices based on Mn-based MHs thus far. This work undoubtedly shows that Mn-based MHs have great application potential in wide color gamut backlight displays and provide a practicable route to fabricate nontoxic, low-cost, and high-performance liquid crystal displays. KEYWORDS: Cs 3 Mn x Zn (1−x) Br 5 , PS, stability, color gamut, backlight display

All-inorganic perovskite CsPbX 3 (X = Cl, Br, I) nanocrystals (NCs) have generated significant attention in the emerging display industry because of their narrow-band emission, high color purity, and facile preparation and processing. By controlling the deposition of Ag nanoparticles in the B−Si−Zn glass matrix, CsPbBrI 2 NC glass with significantly enhanced photoluminescence (PL) intensity (about 6.3 times) was successfully prepared, and the photoluminescence quantum yield (PLQY) is increased from 12.4% to 36.9%. More meaningfully, the high-performance glass powders were incorporated into polystyrene (PS) films through solution and blending techniques, and the films prepared by the latter had superior color coordinates and environmental stability, particularly the intense blue light stability. Under conditions of 60 °C, 90% relative humidity (RH), and 10 000 nit blue light irradiation for 40 d, the PL intensity decline rate of blended film does not exceed 5%. In addition, the light conversion film based on Ag@CsPbBrI 2 glass with CsPbBr 3 glass powders exhibits a wide color gamut of 125.2% of the NTSC 1953 standard, which shows richer colors than commercial displays on the liquid crystal display (LCD) screen, further opening the space for the development of the quantum dot film industry.

Nowadays, an all-inorganic metal halide perovskite (CsPbX 3 , X = Cl, Br, and I) has shown excellent prospects in liquid crystal display (LCD) backlight device applications. However, in order to better meet the market's development, the stability of CsPbX 3 still remains an urgent problem to be solved. Herein, a heat-water cyclic process of CsPbBrI 2 glass powder (RGP) designed to improve stability is proposed. Excitingly, the treated RGP shows better optical properties and heat resistance. Moreover, RGP@PS was prepared with high blue light, water, and heat stabilities. It is particularly noteworthy that RGP6@PS was continuously exposed for 268 h at 60 °C and 90% relative humidity in the blue light (447 nm, 880 W/m 2 ) environment with no decrease in brightness. It illustrates that the CsPbX 3 films have made an important breakthrough in stabilities. The LCD device based on RGP@CsPbBr 3 @PS was designed with a wider color gamut (126%) compared with NTSC 1953. This study explores a new strategy to improve the stability of CsPbX 3 thin films for LCD light conversion films.