Three cationic iridium(III) complexes with 1,10-phenanthroline or compounds containing 1,10-phenanthroline unit as auxiliary ligands: Synthesis and application in polymer light-emitting diodes

Abstract Three yellow-green phosphorescent cationic iridium(III) complexes [(CBT) 2 Ir(phen)]PF 6 , [(CBT) 2 Ir(BCP)]PF 6 and [(CBT) 2 Ir(o-phen)]PF 6 were synthesized ( phen : 1,10-phenanthroline, BCP : bathocuproine, o-phen : 2-(4-tert-butylphenyl)-5-(4-(1-ethyl- H -imidazo[4,5- f ][1,10]phenanthrolin-2-yl)phenyl)-1,3,4-oxadiazole, CBT : 2-(9-(2-ethylhexyl)-9 H -carbazol-3-yl)benzo[ d ]thiazole). All of them were successfully applied in polymer light-emitting diodes: ITO/PEDOT: PSS (40 nm)/PVK: PBD: complex (mass ratios 100: 40: x , x = 1.0, 3.0, and 5.0) (80 nm)/CsF (1.5 nm)/Al (100 nm). The maximum luminances were 8733 cd m −2 , 8878 cd m −2 and 13019 cd m −2 , the maximum luminance efficiencies were 13.7 cd A −1 , 12.5 cd A −1 and 17.5 cd A −1 respectively. Because the steric hindrance of two methyls increase the distance between central Ir 3+ and BCP, and the conjugated plane of 1,10-phenanthroline unit in BCP are distorted by two benzene rings, the flow of electrons are partly hindered, [(CBT) 2 Ir(BCP)]PF 6 exhibits the lowest electroluminescent performances. Due to the electron-transporting functional group 2,5-diphenyl-1,3,4-oxadiazole and hole-transporting functional group carbazole providing good bipolar property, [(CBT) 2 Ir(o-phen)]PF 6 exhibits the best electroluminescent performances.