Two Green-Phosphorescent Iridium Complexes with 2-Phenylpyrimidine Derivatives and Tetraphenylimidodiphosphinate for Efficient Organic Light-Emitting Diodes

Two phosphorescent Ir-III complexes Ir1 and Ir2 containing 5-fluoro-2-[4-(trifluoromethyl)phenyl]pyrimidine and 2-(3,4-difluorophenyl)-5-fluoropyrimidine as cyclometalated main ligand and tetraphenylimidodiphosphinate as ancillary ligand were synthesized. Ir1 was characterized by single-crystal X-ray crystallography. Ir1 and Ir2 show green emissions peaking at 527 and 513 nm, respectively. By using the two complexes as emitters, organic light-emitting diodes (OLEDs) with the structure of TAPC (1,1-bis[4-(di-p-tolylamino)phenyl]cyclohexane, 40 nm)/Ir1 or Ir2 (10 wt.-%):mCP (1,3-bis(9H-carbazol-9-yl)benzene, 20 nm)/TmPyPB (1,3,5-tris(m-pyrid-3-ylphenyl)benzene, 30 nm)/LiF (1 nm)/Al (100 nm) showed high performance with maximum current efficiencies as high as 81.91 or 71.17 cdA(-1) and maximum external quantum efficiencies of 20.8 or 21.3%, respectively. The low-efficiency roll-off ratios of the two devices suggest that the two complexes have potential applications in OLEDs.