Secondary Metal-Ligand Interactions Supported Copper(I) Emitters for High-Efficiency OLEDs

The most prominent way of tuning optoelectronic properties of copper(I) emitters is primary-sphere ligand engineering, but little attention has been placed on noncovalent interactions. Here we demonstrate an effective strategy to introduce secondary metal-ligand interactions into two-coordinate Cu(I) emitters with the goals of optimizing conformation dynamics and improving optical properties. As a proof of concept, a panel of Cu(I) complexes are developed via chalcogen-heterocyclic engineering on the 1,2-positions of carbazole ligand. These complexes have distinct noncovalent metal-ligand interactions mainly originating from chalcogen···Cu and Cu···chalcogen−C orbital interactions, verified by single-crystal structure and theoretical simulation. Thanks to confined conformations and reduced ligand-ligand rotation freedom, the optimized Cu(I) emitters afford high emission quantum yields of up to 93% together with large radiative rate constants of up to 1.2 ×106 s−1. This work unlocks the large potential of noncovalent interactions in developing excellent Cu(I) emitters for cost-effective and high-efficiency OLEDs.