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).