Daisaku Tanaka

Ultra High Efficiency Green Organic Light-Emitting Devices

We developed ultra high efficiency green organic light-emitting devices (OLEDs) using a novel electron transport material containing dipyridylphenyl moieties and green phosphorescent emitter, fac tris(2-phenylpyridine)iridium, Ir(ppy)3. An OLED with a simple structure of glass/indium–tin oxide/polymer buffer layer/arylamine derivative as a hole transport layer/Ir(ppy)3-doped dicarbazolylbiphenyl as an emitter layer/dipyridylphenyl derivative as an electron transport layer/LiF/Al exhibited low drive voltages, which were 2.5 V at 100 cd/m2 and 2.9 V at 1000 cd/m2. High external quantum efficiencies of 29% at 100 cd/m2 and 26% at 1000 cd/m2 were also observed, which lead to the ultra high power efficiencies of 133 lm/W at 100 cd/m2 and 107 lm/W at 1000 cd/m2.

Novel Four-Pyridylbenzene-Armed Biphenyls as Electron-Transport Materials for Phosphorescent OLEDs

A series of four-pyridylbenzene-armed biphenyl derivatives were designed and synthesized as an electron-transport and exciton- and hole-block layer for the fac-tris(2-phenylpyridine)iridium (Ir(PPy)3)-based green phosphorescent organic light-emitting devices (OLEDs), giving improved efficiency in comparison to that with both the electron-transport layer of tris(8-hydroxyquinoline)aluminum (Alq3) and the exciton- and hole-block layer of 2,9-dimethyl-4,7-diphenylphenathroline (BCP).