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.