Highly electroluminescent copper(I) complexes supported by a naphthalene-fused amidocarbene

Herein, a new carbene ligand, naphthalene-fused amido-aminocarbene (NAC), is developed by incorporating a naphthalene substituent into the classic monoamido-aminocarbene (MAC*) framework. This strategy enhances π-electrophilicity of the carbene center while preserving its strong σ-donor nature. By incorporating various amide ligands, a series of NAC-supported copper(I) amide emitters (NAC-1‒NAC-4) are synthesized to exhibit distinct orange thermally activated delayed fluorescence (TADF) from ligand-to-ligand charge transfer excited states. These complexes achieve high photoluminescence quantum yields (up to 0.94), fast radiative rates (up to 1.96×106 s−1), and sub-microsecond lifetimes (as short as 479 ns) in thin films. The resulting organic light-emitting diodes (OLEDs) based on these emitters demonstrate orange emission at 570‒580 nm and achieve high external quantum efficiencies (EQEs) of up to 25.9% at maximum and 25.6% at 1,000 nits, with ultralow efficiency roll-off character (1.2% at 1,000 nits and 13.1% at 10,000 nits), among the best performance reported for orange-to-red Cu(I) emitters. Furthermore, a hyperfluorescent OLED using NAC-1 as a sensitizer achieves a remarkable EQE of 33.0% with an orange-red emission at 584 nm and a small full-width at half maximum of 52 nm. These results underscore the significant potential of the NAC ligand in developing luminescent metal complexes for high-efficiency OLEDs.