High triplet energy hole transport materials based on novel fused indole core structure were synthesized and their device performances in deep blue phosphorescent organic light emitting diodes (PHOLEDs) were investigated. The fused indole based hole transport materials showed a high triplet energy over 2.90 eV and high glass transition temperature over 120 °C. The high triplet energy hole transport materials were used in deep blue PHOLEDs and gave a high external quantum efficiency of 24.7% with a color coordinate of (0.137,0.182).