Zn-Doped Organic–Inorganic Hybrid Mn(II) Halides with Ultra-High PLQY and Stability for Eco-Friendly Display Backlights

To address the issues of Pb toxicity and stability in traditional lead halide perovskite materials, this study presented an environmentally benign aqueous-phase synthesis method for the fabrication of a series of high-performance, green-emitting, lead-free organic–inorganic hybrid manganese(II) halide (OIMnHs) materials, (C12H28N)2Mn(1–x)ZnxBr4. Through Zn2+ doping, the optical properties and stability of the materials were significantly enhanced. Notably, (C12H28N)2Mn0.95Zn0.05Br4 exhibited a remarkable photoluminescence quantum yield (PLQY) of 97.2% and narrow-band green emission at 520 nm with a full width at half-maximum (fwhm) of 43 nm. Furthermore, (C12H28N)2Mn0.95Zn0.05Br4@PET composite films, fabricated via a double-layered PET film encapsulation technique, demonstrated exceptional environmental stability, including resistance to air, heat, water, and blue light. Finally, by integrating (C12H28N)2Mn0.95Zn0.05Br4 with commercial K2SiF6:Mn4+ red phosphor, a composite light conversion film was developed, achieving an impressive wide color gamut coverage of 116.73% NTSC 1953 and 86.82% Rec. 2020. Importantly, the aqueous-phase method exhibited excellent scalability, as demonstrated by a successful 20-fold scale-up production without compromising the optical properties or crystal structure of the materials, highlighting its potential for large-scale manufacturing. This study paved the way for the development of high-performance, environmentally friendly, low-cost, and readily scalable lead-free halide materials for wide-color-gamut backlight displays.