[(CH3)4N]2Mn0.6Zn0.4Br4: Lead-free MnII-based hybrid halide with high photoluminescence quantum yield for backlight displays

High efficient lead halide perovskites with wide-color gamut properties have emerged as new candidates for backlight displays. However, the toxicity of lead and the instability of halide perovskites greatly limit their practical applications. Herein, the luminescent powders of [(CH3)4N]2MnBr4 and [(CH3)4N]MnBr3 were synthesized via a simple yet robust solvent evaporation method. [(CH3)4N]2MnBr4 with tetrahedral coordination Mn2+ and [(CH3)4N]MnBr3 with octahedral coordination Mn2+ show green at 517 nm and red emission peaks at 620 nm, respectively, originating from the 4T1-6A1 transition of Mn2+. To enhance optical of manganese halide via effective alloying, Zn2+-doped [(CH3)4N]2MnBr4 was successfully prepared, and the quantum efficiency of [(CH3)4N]2Mn0.6Zn0.4Br4 was as high as 65%. Furthermore, [(CH3)4N]2Mn0.6Zn0.4Br4 exhibits better optical and thermal stability compared to [(CH3)4N]2MnBr4. [(CH3)4N]2Mn0.6Zn0.4Br4@CsPbBr1.2I1.8 light conversion films with different green-to-red ratios are placed in backlight display devices, and their color gamut exceeds 106% of the National Television Standards Committee (NTSC) 1953 standard, which is superior to the currently reported Mn-based perovskite. This work broadly shows that the [(CH3)4N]2Mn0.6Zn0.4Br4 will provide effective route to fabricate stable and high-performance lead-free liquid crystal displays.