Mixed-Ligand Engineering to Enhance Luminescence of Mn-Based Metal Halides for Wide Color Gamut Display.

Lead-free Mn-based metal halide materials are now being considered as clean candidates for backlight displays and lights due to the d-d transition, diverse components, and environmental friendliness. Therefore, efficient and stable Mn-based metal halide phosphors are in great demand for practical applications. In this work, adopting the mixed-ligand strategy, a series of [(CH)N][(CH)N]MnCl phosphors were synthesized by mechanochemical process. With the increase molar ratio of (CH)N/(CH)N, the phase of phosphors is transformed from orthorhombic to tetragonal. Compared to [(CH)N]MnCl and [(CH)N]MnCl phosphors, the mixed-ligand strategy significantly boosts the green emission intensity of Mn-based metal halide phosphors. The obtained [(CH)N][(CH)N]MnCl phosphors exhibit a high photoluminescence quantum yield (PLQY) of 83.78% under 450 nm excitation, which is attributed to the modulation of the adjacent [MnCl]- distance by using the different chain length of organic cations, effectively suppressing non-radiative recombination. Additionally, the [(CH)N][(CH)N]MnCl phosphors exhibit a green emission at 516 nm, narrow full width at half-maximum (FWHM) of 45.53 nm, and good thermal stability. The constructed white light-emitting diode (WLED) device exhibits a wide color gamut of 108.3% National Television System Committee, demonstrating the suitability of the [(CH)N][(CH)N]MnCl phosphors as a green emitter for WLED displays and lightings. This work provides a new way to modulate the PL performance of manganese-based metal halides for application in the optoelectronic field.