Ultrafast Self-Assembly of Efficient Blue-Excitable Hybrid Manganese Bromide Microcrystals for Wide-Gamut Display...

Blue-excitable lead-free metal halide microcrystals (MCs) with high efficiency and narrow emission are highly desired for next-generation wide-gamut displays. Herein, an ultrafast self-assembly strategy is developed to prepare hybrid manganese bromide MCs with tunable alkyl-chain lengths. With increasing alkyl-chain length, the emission intensity of the obtained MCs first improves significantly and then deteriorates, accompanied by a gradual narrowing of the full width at half maximum (FWHM) from 46.37 to 41.97 nm. The optimized [(C₂H₅)₄N]₂MnBr₄ MCs exhibit strong narrow-band green emission at 518 nm with a FWHM of 43.30 nm and a high photoluminescence quantum yield of 98.70% under 455 nm excitation. This superior emission performance is ascribed to cooperative weak interactions, an appropriate Mn-Mn distance, and highly localized electronic transitions within isolated [MnBr₄]^2- tetrahedra. Moreover, the [(C₂H₅)₄N]₂MnBr₄ MCs show moderate thermal stability, retaining 52.03% of their initial emission intensity at 413 K. By integrating [(C₂H₅)₄N]₂MnBr₄ with K₂SiF₆: Mn⁴⁺ red phosphors on a blue chip, a white light-emitting diode with a high luminous efficacy of 134.60 lm/W and a wide gamut of 112.6% NTSC is achieved, demonstrating the great promise of ultrafast-assembled hybrid manganese bromides for efficient and wide gamut display backlighting.