LAUSR

Abstract Two novel sky-blue iridium(III) complexes Ir(dfppy)2pypzpy and Ir(dfppy)2phpzpy were synthesized, in which 2-(2,4-difluorophenyl)pyridine (dfppy) was used as main ligand, 2,2'-(1H-pyrazole-3,5-diyl)dipyridine (pypzpy) and 2-(3-2-(3-phenyl-1H-pyrazol-5-yl)pyridine (phpzpy) were introduced as the ancillary ligands, respectively. Both Ir(III) complexes showed similar emissions peaked at 469 and 472 nm with high quantum efficiencies of 0.82 and 0.86, respectively. Moreover, the organic light-emitting diodes (OLEDs) with the structure of ITO/HATCN (hexaazatriphenylenehexacabonitrile, 5 nm)/TAPC (bis[4-(N,N-ditolylamino)-phenyl] cyclohexane, 40 nm)/mCP (1,3-bis(9H-carbazol-9-yl)benzene, 5 nm)/Ir(dfppy)2pypzpy or Ir(dfppy)2phpzpy (10 wt%): PPO21 (3-(diphenylphosphoryl)-9-(4- (diphenylphosphoryl)phenyl)-9H-carbazole, 10 nm)/TmPyPB (1,3,5-tri[(3-pyridyl)-phen-3-yl] benzene, 30 nm)/LiF (1 nm)/Al (100 nm) exhibited high efficiency with low efficiency roll-off. Especially, the device based on Ir(dfppy)2phpzpy complex shows the better device performances with a maximum luminance of 38 200 cd/m2, a maximum current efficiency of 58.74 cd/A, a maximum power efficiency of 49.85 lm/W and a maximum external quantum efficiency of 29.30% with Commission Internationale de 1'Eclairage (CIE) color coordinates at (0.18, 0.34).