Photoluminescence Enhancement in Zero-Dimensional Hybrid Copper Halide Single Crystals

Zero-dimensional (0D) organic–inorganic hybrid metal halides (OIHMHs) are excellent luminescent semiconductor materials due to their unique optoelectronic properties. The phase-transition-induced emission modulation of the OIHMHs under external stimuli, such as heat and pressure, has been demonstrated. Recently, the modulation of self-trapped exciton (STE) emission by fine lattice distortion has also attracted considerable attention. However, the role of these structural modulations in exciton recombination pathways remains poorly explored. Here, we report the laser-induced photoluminescence intensity enhancement in 0D OIHMHs, using 1-butyl-1-methylpiperidinium copper bromide [(Bmpip)2Cu2Br4] microcrystals (MCs). The photoluminescence intensity of the MCs increases significantly with a change in the emission color from a green-red dual emission to a yellow emission. Correspondingly, the emission spectrum changes from a distinct bimodal green-to-red profile to a broad yellow band. The results of excitation wavelength-dependent, time-resolved, and temperature-controlled fluorescence, as well as single-crystal X-ray diffraction studies, suggest that the transition from the green-to-red dual emission, delayed by the STE trapping and detrapping process, to the yellow emission occurs by laser-induced Cu–Cu coordination changes that suppress the exciton trapping process. These findings provide insights into the impact of photoexcitation on the performance of the OIHMHs and provide a potential approach for optical modulation to optimize them for photonic applications.