Stimuli-responsive Photoluminescent Copper(I) Halides for Scintillation, Anticounterfeiting and LED Applications

Highly sensitive stimuli-responsive multifunctional luminescent materials are crucial for applications in optical sensing, high-level security, and anticounterfeiting. Here, we report two zero-dimensional (0D) hybrid copper(I) halides, (TEP) Cu Br and (TEP) Cu Br , which are comprised of isolated [Cu Br ] and [Cu Br ] inorganic cluster units, respectively, separated by TEP (TEP = tetraethylphosphonium) cations. (TEP) Cu Br and (TEP) Cu Br demonstrate ultrabright greenish-white and orange-red emissions, respectively, with near unity photoluminescence quantum yields. Optical spectroscopy measurements and density-functional theory (DFT) calculations reveal that photoemissions of these compounds originate from the formation of self-trapped excitons (STEs) due to the excited-state distortions in the copper(I) halide units. Single crystals of both compounds are radioluminescence (RL) active at room temperature under both X- and γ-rays exposure. The excellent energy resolution values and light yields up to 15,800 ph/MeV under 662 keV γ-rays of Cs suggest their potential for scintillation applications. Remarkably, (TEP) Cu Br and (TEP) Cu Br are interconvertible through external chemical stimuli or reverse crystallization. In addition, both compounds demonstrate luminescence on-off switching upon thermal stimuli. The sensitivity of (TEP) Cu Br and (TEP) Cu Br to the chemical and thermal stimuli coupled with their ultrabright emission allows their consideration for practical applications such as solid-state lighting, sensing, information storage, and anticounterfeiting.