Efficient Mn 2+ Red Emission in a Hybrid Halide Induced by Octahedral Distortion

Abstract Manganese(II)‐based (Mn 2+ ) hybrid halides are promising lead‐free red phosphors; however, achieving high external quantum efficiency (EQE) remains challenging due to spin‐forbidden d–d transitions and nonradiative losses. A structurally rigid hybrid halide, (MAMP)MnCl 3 ·Cl [MAMP = 2‐((methylamino)methyl)pyridine], is reported, comprising face‐sharing [MnCl 6 ] 4− chains stabilized by N─H···Cl hydrogen bonds and π–π interactions from the organic cation. This structural framework suppresses nonradiative recombination, enabling bright red emission at 655 nm with an EQE of 43.9%. The internal quantum efficiency (IQE) reaches 70.8%, indicating efficient radiative recombination. The material also exhibits good thermal stability ( T 50 = 390 K) and a strong luminescent response under X‐ray excitation. Density functional theory calculations indicate a direct bandgap with dominant Mn 3d orbital character. Integration into light‐emitting diode (LED) devices demonstrates practical utility, with a white‐light LED showing excellent color rendering ( R a = 90.6, R 9 = 91.6) and a red LED maintaining stable spectral output. These findings establish a rational design approach for Mn 2+ ‐based hybrid phosphors in next‐generation optoelectronic applications.