Dual-emissive luminescence in OIHMH single crystals: tunable red-green emissions via Mn2+ doping and theoretical insights

Abstract

The burgeoning demand for materials with tunable photoluminescence properties for applications has necessitated the exploration of novel luminescent materials. This study presents the synthesis and characterization of a novel 0D organic–inorganic hybrid metal halide (OIHMH) single crystal, C₆H₁₄N₂CdBr₄, which exhibits intriguing luminescent properties upon Mn²⁺ doping. The introduction of single Mn²⁺ ions results in a dual-emission, with the unexpected emergence of a red emission peak at 627 nm, in addition to the conventional tetrahedral green emission at 525 nm. This dual-emission is attributed to the distinct inter-tetrahedral distances within the crystal structure of C₆H₁₄N₂CdBr₄ with varying distances between [CdBr₄]²⁻ tetrahedra, influencing the spatial distribution and interaction of the [MnBr₄]²⁻ tetrahedra. Electron paramagnetic resonance (EPR) spectroscopy and theoretical calculations reveal the 627 nm and 525 nm emissions are attributed to the d–d transition of magnetic coupled Mn²⁺–Mn²⁺ pairs and isolated Mn²⁺ ions, respectively. This study not only advances the understanding of the luminescence mechanisms of Mn²⁺ but also paves the way for the development of tunable luminescent materials.