Orange and White Electrophosphorescence Based on Triphenylamine-Fluorenyl Trifluoromethylpyridine Iridium Complexes

Novel complexes bis[2-(9,9-bis(4-diphenylaminophenyl)fluoren-2-yl)-5-trifluoromethylpyridinato-C3,N] iridium(acetyl acetonate) (7) and bis[2-(9,9-bis(4-diphenylaminophenyl)fluoren-2-yl)-5-trifluoromethylpyridinato-C3,N] iridium (2-picolinic acid) (8) were prepared. Trifluoromethyl group and 2-picolinic acid were introduced to tune luminescent emission. Triphenylamine (TPA)-fluorene with large steric hindrance was incorporated to enhance the hole-injection and hole-transport abilities for phosphorescent material, to suppress intermolecular interaction and to shorten fluorescence lifetime. The orange-emissive electrophosphorescent devices for 7 and 8 exhibited stable electroluminescent (EL) peaks at 580 (or 585) and 572 (or 576) nm under a certain concentration at the different bias voltage, and maximum current efficiencies of 32.2 and 35.6 cd/A. The white-emissive devices of the dual emitting layer based on the orange (7 or 8) and blue (FIrPic) phosphor showed CIE coordinates of (0.33, 0.41) and (0.31, 0.40), and maximum current efficiencies of 8.9 and 13.8 cd/A. The CIE coordinates with the increasing voltage were stable. High efficiency and slow decay of devices indicated that 7 and 8 were highly efficient orange emitters.