[(CH₃)₄N]₂Mn_0.6Zn_0.4Br₄: Lead-free Mn^II-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]₂Mn_0.6Zn_0.4Br₄ was as high as 65%. Furthermore, [(CH₃)₄N]₂Mn_0.6Zn_0.4Br₄ exhibits better optical and thermal stability compared to [(CH₃)₄N]₂MnBr₄. [(CH₃)₄N]₂Mn_0.6Zn_0.4Br₄@CsPbBr_1.2I_1.8 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]₂Mn_0.6Zn_0.4Br₄ will provide effective route to fabricate stable and high-performance lead-free liquid crystal displays.