Highly Efficient Copper(I) Emitters Supported by Secondary Metal-Ligand Interactions

The most prominent way of tuning optoelectronic properties of copper(I) emitters is primary-sphere ligand engineering, but little attention is placed on noncovalent interactions. Here, an effective strategy is demonstrated to introduce secondary metal-ligand interactions into two-coordinate Cu(I) emitters with the goals of optimizing conformations and improving optical properties. As a proof of concept, a panel of Cu(I) complexes is developed via chalcogen-heterocyclic engineering on the 1,2-positions of carbazole ligand. The S-embedded complexes have distinct noncovalent metal-ligand interactions originating from S center dot center dot center dot Cu orbital contacts, verified by single-crystal structure and theoretical simulation. Thanks to the flattened conformations stabilized by secondary metal-ligand interactions, the optimized Cu(I) emitters afford high emission quantum yields of up to 93% and short radiative lifetimes of down to 0.8 mu s. Cu-12BT and Cu-12BF support the resultant organic light-emitting diodes (OLEDs) delivering outstanding maximum external quantum efficiencies (EQEs) of 24.3% and 28.6%, respectively, among the best performance for Cu(I) emitters. The optimal devices based on Cu-12BF also achieve 18.7% EQE at the practical luminance of 100 nits. This work unlocks the large potential of noncovalent interactions in developing excellent Cu(I) emitters for cost-effective and high-efficiency OLEDs. A panel of Cu(I) carbene-metal-amide complexes featuring secondary metal-ligand interactions are developed via chalcogen-heterocyclic engineering. These complexes exhibit high emission quantum yields and fast radiative rates. The respective organic light-emitting diodes deliver record-high external quantum efficiencies of up to 28.6%. image