Solution processable organic electro-phosphorescent iridium complex based on a benzothiazole derivative

We have synthesized a new solution processable iridium complex, di[2-(4′-octyloxyphenyl) benzothiazole]iridium(III)acetoacetone, [(OPBT)2Ir(acac)], based on benzothiazole derivative for organic electro-phosphorescent devices. The synthesized molecule was identified by 1H NMR and 13C NMR, and readily soluble in common organic solvents such as chlorobenzene. The UV-visible absorption and photoluminescence properties of pristine [(OPBT)2Ir(acac) thin film as well as poly(N-vinylcarbzole) (PVK) thin film doped with the iridium complex were studied. The maximum UV-visible absorption and photoluminescence (PL) spectra are found to be at 337 nm and 547 nm, respectively. We have fabricated phosphorescent organic light-emitting devices using the ITO/PEDOT:PSS (40 nm)/PVK:(OPBT)2Ir(acac) (40 nm)/Balq (40 nm)/LiF (1 nm)/Al (80 nm) configuration with the iridium complex as a triplet emissive dopant in poly(N-vinylcarbazole) (PVK) host. The electroluminescence (EL) devices showed greenish yellow light emission with maximum peak at 551 nm. Especially, the maximum external quantum and current efficiency of 1 mol% doped device were 1.74% and 4.89 cd/A, respectively.