Electronic Effects of Aromatic Amine Moiety on Red Phosphorescent Iridium(III) Complexes for Solution- Processable OLEDs

A series of new red emitting phosphorescent iridium(III) complexes, (MN-TFP)2Ir(tmd), (MN-TFP)2Ir(dpd), (MN-MQ)2Ir(tmd), (MN-MQ)2Ir(dpd), (MN-Q)2Ir(tmd), and (MN-Q)2Ir(dpd), were synthesized for phosphorescent organic light-emitting diodes (PhOLEDs). The emitters consist of electron-rich and deficient aromatic rings, such as 1-methylnaphthalene (MN), 4-(trifluoromethyl) pyridine (TFP), 4-methylquinoline (MQ), and quinoline (Q). The ancillary ligands were 2,2,6,6-tetramethylheptane3,5-dione (tmd) and 1,3-diphenylpropane-1,3-dione (dpd). The main ligands were synthesized by the Suzuki coupling reaction. The red emitting complexes were synthesized by the Nonoyama reaction. The optical properties were characterized by UV-visible absorption and photoluminescence (PL) spectroscopy. OLED devices with the structure of indium tin oxide (ITO)/PEDOT: PSS (40 nm)/HTL (17 nm)/RH-35: red dopant (5%, 40 nm)/HCL (5 nm)/SNABH 205: 6s-12 (5%, 15 nm)/TPBi (20 nm)/LiF (1 nm)/Al (100 nm) were manufactured. These OLED devices were characterized by an investigation of current density-voltage-luminance, current efficiency, power efficiency, EQE, and EL spectrum. The red emitting iridium(III) complexes will be used as a solution process dopant for the hybrid OLED devices.