High-Efficiency Green-Emission of an Organophosphorus Manganese Chloride for White LED and X-ray Imaging Applications

Manganese halides are emerging as promising alternatives to traditional inorganic phosphors and X-ray scintillators due to their low toxicity, high attenuation coefficients, high light yield, and cost-effective solution-processability. We synthesized a novel manganese chloride, (4CTP)₂MnCl₄ (4CTP = (4-chlorobenzyl)triphenylphosphonium), via solvent volatilization. The crystal exhibits a narrow-band (∼48 nm) green emission at 516 nm under ultraviolet or blue light excitation, attributed to the Mn²⁺ d-d transition, with a photoluminescence quantum yield (PLQY) of 95.7% and a nearest Mn···Mn distance of 9.909 Å. A white light-emitting diode (LED) for backlight displays was fabricated using (4CTP)₂MnCl₄, a 450 nm blue LED chip, and K₂SiF₆: Mn⁴⁺, achieving a color gamut of 112.1% at 20 mA. Substituting the red phosphor with (Sr, Ca)AlSiN₃: Eu²⁺ produced a white LED for solid-state lighting with a color rendering index (CRI) of 92.4 and a correlated color temperature (CCT) of 4097 K. The crystal also demonstrated excellent X-ray scintillation properties (a light yield of 63,400 photons/MeV). A flexible (4CTP)₂MnCl₄@PMMA film enabled high-resolution X-ray imaging (10.4 lp/mm). This work showcases a simple route to develop high-performance manganese halides for LEDs and X-ray imaging.