Synthesis and electrophosphorescent properties of iridium complexes based on phenylpyridine-based main ligand for organic light-emitting diodes

A novel cyclometalated ligand 2-(2,4-dimethoxyphenyl)-5-trifluoromethylpyridine (MeO2CF3ppy) and its complexes bis[2-(2,4-dimethoxy-phenyl)-5-trifluoromethyl pyridinato-N,C2`]iridium 2-pyrazine carboxylic acid (MeO2CF3ppy)2Ir(prz) and bis[2-(2,4-dimethoxy-phenyl)-5-trifluoromethyl pyridinato-N,C2`]iridium 5-methyl-2-pyrazine carboxylic acid (MeO2CF3ppy)2Ir(mprz) were synthesized. Trifluoromethyl and dimethoxy groups were introduced into main ligand for tuning the emission color. The phosphorescence organic light-emitting diodes (PhOLEDs) based on these complexes with the configuration of ITO/PEDOT:PSS (40 nm)/PVK:TCTA:OXD-7:Ir complex (50 nm)/BCP (20 nm)/Alq3 (10 nm)/LiF (1 nm)/Al (100 nm) were fabricated. The solution-processed PhOLEDs based on (MeO2CF3ppy)2Ir(mprz) exhibited a maximum quantum efficiency of 2.97% and luminance efficiency of 4.95 cd/A with CIE coordinate of (0.43, 0.53).