Efficient green carbene-copper(I)-amide complexes enabled by a pyrimidine-fused N-heterocyclic carbene ligand
Copper(I)-based carbene-metal-amide (CMA) emitters offer an earth-abundant alternative to precious-metal phosphors for organic light-emitting diodes (OLEDs), yet efficient green emission remains scarce due to limited π-extension and unbalanced charge-transfer characteristics of N-heterocyclic carbene (NHC) ligands. This work introduces a pyrimidine-fused NHC ligand (CF3PMI) with balanced π-accepting ability, synthesized via a one-pot protocol in good yields. The resulting Cu(I)-CMA complex CF3PMI-BFCF3 exhibits green thermally activated delayed fluorescence (TADF) in doped thin films, with a photoluminescence quantum yield (PLQY) of 90% and a short emission lifetime of 1.16 μs. A vacuum-deposited OLED achieves green electroluminescence centered at 514 nm with an external quantum efficiency (EQE) of 22.7%. Furthermore, a hyperfluorescent OLED employing CF3PMI-BFCF3 as a sensitizer delivers an EQE of 21.8%, green emission at 537 nm, and a narrow full width at half maximum (FWHM) of 30 nm. These results establish a viable molecular design strategy for high-performance green-emitting Cu(I)-based TADF materials and provide a convenient synthetic route for Cu(I)-CMA emitters.