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

Abstract

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)₂Ir(acac), (ttq)₂Ir(acac) and (tptq)₂Ir(acac), were designed and synthesized by utilizing extended π-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.