Narrow‐Band Green‐Emitting Manganese (II) Hybrids Single Crystal with Record External Quantum Efficiency Under Blue Light Excitation

A bright green‐emitting Mn 2+ ‐based halide single crystal, [Et(Ph) 3 P] 2 MnBr 4 , has been successfully grown, exhibiting green emission that peaks at 523 nm and achieving a record external quantum efficiency of 82.1% under 450 nm excitation. This impressive efficiency is attributed to the long Mn 2+ –Mn 2+ distance resulting from the separation of large organic cations, along with minimal defects and boundaries within the single crystal. A white light emitting diode (LED) fabricated from this halide has achieved a high luminous efficiency of 121.3 lm W −1 and a color gamut coverage of 108.7% National Television System Committee (NTSC) standard. Additionally, liquid crystal display (LCD) utilizing a white LED strip made with synthesized manganese hybrids for backlighting produce images that are more vivid and colorful than those generated by commercial white LEDs based on Y 3 Al 5 O 12 :Ce 3+ phosphor. Furthermore, this halide exhibits significant piezochromism, shifting from green to red upon compression, with an ultrabroad tunability of 105 nm observed below 5.93 GPa. These findings underscore the promising potential of [Et(Ph) 3 P] 2 MnBr 4 hybrid halide for backlighting and visual pressure sensing applications.