Synthesis and Characterization of Copper(I) Halide Heteroleptic Complexes with Thermally Activated Delayed Fluorescence

In the global context of green chemistry and sustainable development, luminescent copper(I) halide complexes hold broad applications, attributed to their abundant resources and excellent photophysical properties. Herein, two novel copper(I) halide complexes were synthesized and systematically investigated using single-crystal X-ray diffraction, photophysical characterization, and theoretical calculations among other methods. Both solid-state complexes exhibit bright green luminescent emissions with low self-absorption rates. The photoluminescence quantum yields (PLQYs) are as high as 95% and 87%, respectively. Because their singlet–triplet energy gaps (ΔE_ST) are very small, both being 0.10 eV, these complexes can achieve thermally activated delayed fluorescence emission through efficient reverse intersystem crossing. Theoretical calculations revealed that their high-efficiency luminescence arises from the synergistic effects of metal-to-ligand charge transfer, halogen-to-ligand charge transfer, and ligand-to-ligand charge transfer.