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.