Heteroatom N/O Induced Dual-Band Emission of Hybrid Cuprous Iodide Single Crystals for Anticounterfeiting Applications

Organic-inorganic hybrid cuprous halides demonstrate remarkable optoelectronic applications due to their structural diversity, low cost, and nontoxicity. However, elucidating their diverse luminescence mechanisms remains a key research challenge. Here, novel cuprous iodide-based hybrid materials are constructed by introducing heteroatom N/O-based organic compounds (piperazine and morpholine) as ligands. Single crystals of pip₂Cu₂I₆·H₂O (pip = piperazinium) and mor₄Cu₂I₆·H₂O (mor = morpholinium) were grown by a slow evaporation method. Crystal structures, optical and theoretical band gap, photoluminescence (PL), antimoisture/thermal stability, and preliminary anticounterfeiting applications were systematically studied. Intriguingly, both pip₂Cu₂I₆·H₂O and mor₄Cu₂I₆·H₂O single crystals exhibited the obvious dual-band emission. PL decay lifetime values of pip₂Cu₂I₆·H₂O single crystals under 325 and 365 nm excitation are approximately 15.817 and 4.914 μs, respectively, while mor₄Cu₂I₆·H₂O single crystals possess the PL decay lifetime values of approximately 5.809 and 6.406 μs under the same excitation conditions, whose emission mechanisms are both attributed to halide/metal to ligand charge-transfer (X/MLCT) and cluster-centered (CC) excited states, rather than multiple exciton generation (MEG) processes. This work not only deepens the understanding of structure-property relationships in hybrid cuprous halide materials, but also provides significant references to the constructions and fabrications of hybrid cuprous halide-based multifunctional optoelectronic devices.