Phthalonitrile based charge transfer type host for yellow phosphorescent organic light-emitting diodes

An phthalonitrile based 3,3''-di(9H-carbazol-9-yl)-1,1':2′,1''-terphenyl]-4′,5′-dicarbonitrile (IPNCz) was explored as a charge transfer type host of a yellow emitting bis(4-phenyl-thieno3,2-c]pyridinato-C2,N)(acetylacetonato)iridium(III) (PO-01) dopant. The phthalonitrile unit was an electron deficient unit and 9-phenylcarbazole was an electron rich unit of the IPNCz host. The phthalonitrile unit combined with the phenylcarbazole unit allowed strong charge transfer character by the donor-acceptor structure, delivering good thermal stability, bipolar carrier transport and proper triplet energy. Therefore, the IPNCz host assisted low driving voltage and high quantum efficiency close to 25% in the yellow phosphorescent device.