Triplet emitter doped exciton harvesting layer for improved efficiency and long lifetime in blue phosphorescent organic light-emitting diodes

•Improved lifetime in blue phosphorescent organic light-emitting diodes by a triplet emitter doped electron transport layer.•Efficiency improvement by an electron transport type exciton blocking layer.•Exciton harvesting effect by triplet emitter doped exciton blocking layer.

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.