Efficient yellow OLEDs based on bis-tridentate iridium(III) complexes with two C∧N∧N-coordinating ligands

Abstract

Four bis-tridentate iridium(III) complexes with two different C∧N∧N-coordinating ligands have been synthesized and characterized. All complexes exhibited yellow/orange emission peaking at 580–604 nm with short lifetimes of 1.4–1.6 μs and medium photoluminescence quantum yields (PLQYs) of 31%–53%. These complexes exhibit good thermal stability with decomposition temperature (Td) exceeding 310 °C. The luminescence efficiency and thermal stability of iridium complexes were improved by the m-substituted CF3 groups. As a result, complex 2 exhibited the highest PLQYs of 0.53 and Td of 348 °C. The OLEDs based on complex 2 showed good performances. The device at 2% doping concentration showed a maximum current efficiency of 36.4 cd A−1, power efficiency of 29.1 lm W−1 and external quantum efficiency (EQE) of 14.4%. These results suggest that these complexes have potential for the application in high-efficiency OLEDs.