Highly efficient red iridium(III) complexes cyclometalated by 4-phenylthieno[3,2-c] quinoline ligands for phosphorescent OLEDs with external quantum efficiencies over 20%

Highly efficient red phosphorescent emitters are highly desired for applications in phosphorescent organic light-emitting diodes (PhOLEDs). To achieve this goal, three novel heterolepic Ir(III) complexes, namely (ptq)(2)Ir(acac), (ttq)(2)Ir(acac) and (tptq)(2)Ir(acac), were designed and synthesized by utilizing extended pi-conjugated thieno[3,2-c] quinoline derivatives as cyclometalating ligands. These complexes display intense red phosphorescence emission in the range of 610-620 nm. Accordingly, a vacuum-deposited red PhOLED based on (ptq) 2Ir(acac) shows the highest external quantum efficiency (EQE) of 22.9% with Commission Internationale de L'Eclairage (CIE) coordinates of (0.61, 0.36). In particular, the device exhibits an extraordinary low efficiency roll-off of 7.8% at a luminance of 1000 cd m(-2).