Dual-emissive luminescence in OIHMH single crystals: tunable red-green emissions Mn doping and theoretical insights.

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, CHNCdBr, which exhibits intriguing luminescent properties upon Mn doping. The introduction of single Mn 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 CHNCdBr with varying distances between [CdBr] tetrahedra, influencing the spatial distribution and interaction of the [MnBr] 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 Mn-Mn pairs and isolated Mn ions, respectively. This study not only advances the understanding of the luminescence mechanisms of Mn but also paves the way for the development of tunable luminescent materials.