Near-Unity Green Luminescent Hybrid Manganese Halides: Ionothermal Synthesis and White Light-Emitting Diode Applications

Zero-dimensional (0D) Mn 2+ -based organic–inorganic metal halides (OIMHs) have garnered significant attention in the field of white light-emitting diodes (WLEDs) due to their low toxicity, high photoluminescence quantum yield (PLQY), small full width at half-maximum (fwhm), and good stability. In this study, we report the synthesis and luminescence characterization of six novel 0D Mn 2+ -based OIMHs with the general formula [R–Ph 3 P] 2 MnX 4 (where R = −CH 3, −C 2 H 5, −C 3 H 5, −Ph, and −CH 2 Ph; X = Cl/Br), which were fabricated via an environmentally friendly minimal-solvent ionothermal method. All compounds exhibit bright green emission (506–523 nm) under blue light excitation, narrow fwhm (43–48 nm), high color purity (87–94%), and high thermal stability (>280 °C). Notably, [PhCH 2 –Ph 3 P] 2 MnBr 2 Cl 2 achieves a near-unity PLQY of 92.76% under 450 nm excitation, while [C 3 H 5 –Ph 3 P] 2 MnBr 2 Cl 2 demonstrates an excellent photoluminescence lifetime of 632.89 μs. A WLED was fabricated by combining [PhCH 2 –Ph 3 P] 2 MnBr 2 Cl 2 with a commercial phosphor and a blue GaN chip (λ em = 450 nm), yielding a correlated color temperature of 5502 K and CIE 1931 color coordinates of (0.312, 0.317). This work not only establishes a green synthesis pathway for high-performance Mn 2+ -based luminescent materials but also offers valuable insights into their application in advanced lighting technologies.