Centimeter‐Sized Single Crystals of Tetrahedral Manganese (II) Halide Hybrids for Wide‐Color Gamut Backlighting Displays

Phosphors with narrow-band green emissions and high photoluminescent quantum efficiency (PLQY) are significantly required for backlighting displays with wider color gamut. In this work, two centimeter-sized manganese (II) halide single crystals TMG₂MnCl₄ and TMG₂MnBr₄ (TMG = 1,1,3,3-tetramethylguanidine) are synthesized, exhibiting bright narrow-band green emissions with high PLQYs up to 62% and 90%, respectively. The narrow-band green light emission is located at 520 nm with a full-width at half-maximum (FWHM) of only 57 nm. The photoluminescence mechanisms of two single crystals are elaborated. Two white-light-emitting diodes for backlighting displays (BD-WLEDs) based on them are fabricated, exhibiting the widest color gamut of 122% National Television Standards Committee (NTSC), and a luminous efficacy reached ≈93 lm W^-1 with excellent luminescence stability at high temperatures. These properties indicate the potential applications of tetrahedral manganese (II) hybrids in wide-color gamut backlighting displays.