Efficiency and lifetime improvement of blue phosphorescent organic light-emitting diodes (PHOLEDs) was achieved by introducing a triplet emitter doped exciton harvesting layer. A green triplet emitter doped electron transport layer was the exciton harvesting layer of the blue PHOLEDs, which doubled the lifetime and enhanced the efficiency of the blue PHOLEDs compared with a common electron transport layer. Blocking of triplet exciton quenching of the blue triplet emitter by the exciton harvesting layer was proposed as the main mechanism of improved efficiency and lifetime.