High-efficient phosphorescent iridium(III) complexes with benzimidazole ligand for organic light-emitting diodes: Synthesis, electrochemistry and electroluminescent properties

Two phosphorescent complexes Ir(FFBI)2(pmp) and Ir(FFBI)2(pti) based on cyclometalated ligand 1-(4-fluorobenzyl)-2-(4-fluorophenyl)-1H-benzo[d]imidazole (FFBI) and ancillary ligands 2-(phenyliminomethyl)phenol (pmp) or 3-(pyridin-2-yl)-4,5,6,7-tetrahydro-2H-indazole (pti) were synthesized. The single crystal of Ir(FFBI)2(pmp) was obtained. The light emitting and electrochemical properties of these complexes were studied. The electroluminescent devices based on these two complexes with the structure of ITO/NPB (40 nm)/Ir complex: CBP (30 nm)/BCP (15 nm)/Alq (30 nm)/LiF (1 nm)/Al (100 nm) emitted cyan color, with high brightness and efficiencies. The maximum external quantum efficiencies reached to 6.8% and 11.6%, respectively.