Efficient Blue Photo- and Electroluminescence from CF 3 -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-CF 3 Cz and MAC*-Cu-2CF 3 Cz, by introducing one or two CF 3 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-CF 3 Cz or a dominant phosphorescence nature from local triplet excited state of the carbazole ligand for MAC*-Cu-2CF 3 Cz. Inspiringly, MAC*-Cu-CF 3 Cz 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 5  s -1 order. The resultant vacuum-deposited OLEDs based on MAC*-Cu-CF 3 Cz delivered pure-blue electroluminescence at 462 nm together with a high external quantum efficiency of 13.0 %.