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.