Highly efficient red electrophosphorescence from a solution-processed zwitterionic cyclometalated iridium(III) complex

A mononuclear red-emitting zwitterionic iridium(III) complex, bis(1-(phenyl)isoquinolinato) iridium(III) (2,2′-bipyridine-3-ol-3′-olate), was synthesized and used as a triplet emitter doped in a polymeric host in solution-processed electrophosphorescent light-emitting diodes. We achieved a high luminous effieciency (LE) of 12.62cd∕A with fast response time in the device using the dopant unlike in the device using cationic irridium(III) phosphorescent materials. A hole transporting polymeric interlayer between the anode and the emitting layer improved the LE and decreased the exciton quenching at high electric fields.