Hydrogen Bonding-Induced Synergistic Effect on Second-Harmonic Generation and High Photoluminescence of Morpholinium Cuprous Bromide Dihydrate Single Crystals

Hybrid cuprous halides have attracted great attention in optoelectronic fields due to their low cost, abundant structural diversity, and highly efficient luminescence. However, there have been ambiguous issues about the crystal structure and photoluminescence characteristics of morpholinium cuprous bromide. Here, hydrogen bonding induced a synergistic effect on second-harmonic generation and highly efficient photoluminescence of hybrid cuprous halides was observed. Morpholinium cuprous bromide dihydrate (mor₄Cu₂Br₆·2H₂O) single crystals were grown in HBr/CH₃CN and H₃PO₂ solution by a slow evaporation method. Interestingly, mor₄Cu₂Br₆·2H₂O exhibited the triclinic crystal system <i>P</i>1 (no.1), which showed the obvious second-harmonic generation effect of 4 × Y-cut quartz. More importantly, mor₄Cu₂Br₆·2H₂O showed highly efficient photoluminescence (PL) located at about 560 nm with a photoluminescence quantum yield (PLQY) of 83.68% attributed to the through space charge transfer (TSCT) mechanism, which clarified the controversial results about the former crystal structure and PLQY exceeding 100% in hybrid cuprous halide systems. Besides, the preliminary anticounterfeiting of these hybrid cuprous bromide and iodide hydrates was demonstrated. This work not only provides the understanding for the structure-property relationship of hybrid cuprous halides, but also paves the way for optoelectronic device design and fabrication of the hybrid cuprous halide systems.