Pyridazine derived bipolar host materials for phosphorescent organic light-emitting diodes

Abstract Two organic materials incited by electron deficiency of a pyridazine moiety were designed for application as bipolar host materials of phosphorescent organic light-emitting diodes. Modification of the pyridazine moiety with carbazole and pyrrolocarbazole hole transport units provided 3,6-bis(2-(9 H -carbazol-9-yl)phenyl)pyridazine (CzPd) and 3,6-bis(2-(3-phenylpyrrolo[3,2- a ]carbazol-10(3H)-yl)phenyl)pyridazine (PCzPd) as bipolar host materials. The 3,6-bis(2-(9 H -carbazol-9-yl)phenyl)pyridazine and 3,6-bis(2-(3-phenylpyrrolo[3,2- a ]carbazol-10(3 H )-yl)phenyl)pyridazine were high triplet energy hosts by ortho- substitution of the hole transport units. Based on the triplet energy of the host materials, green phosphorescent organic light-emitting diodes were devised and the green devices presented high quantum efficiency of 15.5%