Efficient Blue Photo- and Electroluminescence from CF-Decorated Cu(I) Complexes.

Luminescent organometallic complexes of earth-abundant copper(I) have long been studied in organic light-emitting diodes (OLED). Particularly, Cu(I)-based carbene-metal-amide (CMA) complexes have recently emerged as promising organometallic emitters. However, blue-emitting Cu(I) CMA complexes have been rarely reported. Here we constructed two blue-emitting Cu(I) CMA emitters, MAC*-Cu-CFCz and MAC*-Cu-2CFCz, by introducing one or two CF substitutes into carbazole ligands. Both complexes exhibited high thermal stability and blue emission colors. Moreover, two complexes exhibited different emission origins rooting from different donor ligands: a distinct thermally activated delayed fluorescence (TADF) from ligand-to-ligand charge transfer excited states for MAC*-Cu-CFCz or a dominant phosphorescence nature from local triplet excited state of the carbazole ligand for MAC*-Cu-2CFCz. Inspiringly, MAC*-Cu-CFCz had high photoluminescence quantum yields of up to 94 % and short emission lifetimes of down to 1.2 μs in doped films, accompanied by relatively high radiative rates in the 10 s order. The resultant vacuum-deposited OLEDs based on MAC*-Cu-CFCz delivered pure-blue electroluminescence at 462 nm together with a high external quantum efficiency of 13.0 %.