Pure Red Iridium(III) Complexes Possessing Good Electron Mobility with 1,5-Naphthyridin-4-ol Derivatives for High-Performance OLEDs with an EQE over 31%

Three iridium(III) complexes (Ir(4tfmpq)2mND, Ir(4tfmpq)2mmND, and Ir(4tfmpq)2mpND) with the 4-(4-(trifluoromethyl)phenyl)quinazoline (4tfmpq) main ligand and 1,5-naphthyridin-4-ol derivatives (mND: 8-methyl-1,5-naphthyridin-4-ol, mmND: 2,8-dimethyl-1,5-naphthyridin-4-ol, mpND: 8-methyl-2-phenyl-1,5-naphthyridin-4-ol) as ancillary ligands were studied. The complexes (Ir(4tfmpq)2mND, Ir(4tfmpq)2mmND, and Ir(4tfmpq)2mpND) emit pure red emissions of 626–630 nm with high photoluminescence quantum yields of 85.2–93.4% in CH2Cl2 and better electron mobilities than that of tri(8-hydroxyquinoline)aluminum. By employing three pure red emitters, all the phosphorescent organic light-emitting diodes exhibited superior performances with a maximum external quantum efficiency of 31.48% and the efficiency roll-off is very mild, which are among the best results ever reported for pure red organic light-emitting diodes using Ir(III) complexes. In addition, CIE(x, y) coordinates of (0.670, 0.327) are also close to the standard red emission required by the National Television System Committee.