Two Organic–Inorganic Hybrid Manganese Bromides with Highly Efficient Emission toward White LEDs

Organic-inorganic metal halides have attracted great attention due to their tunable structural and spectroscopic properties. Here, two organic-inorganic hybrid manganese bromides, (TEMA)₂MnBr₄ (TEMA = triethylmethylammonium) and (TEBA)₂MnBr₄ (TEBA = benzyltriethylammonium), are synthesized using the evaporation crystallization method. Following a heat-induced phase transition at 363 K, the structure and optical properties of (TEMA)₂MnBr₄ change but return to their initial state upon cooling to room temperature, as confirmed by X-ray diffraction, photoluminescence (PL), and Raman spectra. Meanwhile, (TEBA)₂MnBr₄, with a larger Mn-Mn distance, exhibits a higher photoluminescence quantum yield of 98.1% and greater thermal quenching temperature. However, due to the poorer thermal stability of the organic cation, the crystal melts at 400 K, leading to fluorescence quenching. White LEDs based on (TEMA)₂MnBr₄ and (TEBA)₂MnBr₄ are successfully fabricated with color rendering indices of 97.4 and 97.2, respectively. The investigation provides deep insights into the structural and optical properties of (TEMA)₂MnBr₄ and (TEBA)₂MnBr₄, advancing research for LED display design by tuning organic cations.