A thermally stable aromatic amine derivative with a symmetrically substituted double spirobifluorene core was synthesized as a hole transport material for green phosphorescent organic light-emitting diodes. A high glass transition temperature of 142 degrees C was obtained and a film morphology of the hole transport material was kept stable up to 120 degrees C. The hole transport material showed a high triplet energy of 2.53 eV and a quantum efficiency of 17.4% in green phosphorescent organic light-emitting diodes. (C) 2012 Elsevier B.V. All rights reserved.