An indole derivative as a high triplet energy hole transport material for blue phosphorescent organic light-emitting diodes

• A high triplet energy hole transport material derived from an indole
• High quantum efficiency of 19.3% in deep blue phosphorescent organic light-emitting diodes
• Good thermal stability with a high glass transition temperature of 142 °C

A thermally stable high triplet energy material derived from an indoloacridine core and indole hole transport units, 8,8-bis(4-(1H-indol-1-yl)phenyl)-8H-indolo[3,2,1-de]acridine (BIPIA), was synthesized as the hole transport material for deep blue phosphorescent organic light-emitting diodes. The BIPIA hole transport material showed a high triplet energy of 2.95 eV and high glass transition temperature of 142 °C. A high quantum efficiency of 19.3% was obtained in the deep blue device using BIPIA as the high triplet energy hole transport material.