Highly efficient photoluminescence and excellent stability in hybrid manganese halides: (C₂₁H₂₂N)₂MnBr₄

Manganese-based organic-inorganic hybrid metal halides (Mn-based OIHMHs) have attracted much attention due to their low toxicity, abundant resources and unique optical properties. However, the low photoluminescence quantum yield (PLQY) caused by structural factors and non-radiative recombination caused by high temperature have limited their applications. In this study, a green-emitting organic-inorganic hybrid metal halide, (C₂₁H₂₂N)₂MnBr₄ (C₂₁H₂₂N⁺ = protonated triphenylamine cation), was designed and synthesized to address these issues. This material has a PLQY as high as 94 %. The main reason is that the longer distance between Mn²⁺ ions in the (C₂₁H₂₂N)₂MnBr₄ crystal structure significantly reduces the electron coupling between adjacent Mn centers, thereby inhibiting the non-radiative energy transfer process and thus increasing the PLQY. Additionally, this material exhibits a unique property of increasing luminescence intensity with rising temperature in the range of 40-110 °C, and it has sufficient thermal stability (<180 °C). This breaks the limitation of high-temperature applications. The white light-emitting diodes (WLEDs) fabricated based on this compound feature stable color coordinates and color temperatures, high luminous efficiency, and excellent color rendering index (CRI). Importantly, in comparison to conventional devices, the WLED demonstrates markedly enhanced thermal stability, effectively addressing the issue of efficiency degradation at elevated temperatures that is commonly observed in traditional devices. These advantageous properties render this material system particularly promising for application domains where stringent performance criteria are required for white-light illumination technologies.