Above 30% External Quantum Efficiency in Blue Phosphorescent Organic Light-Emitting Diodes Using Pyrido[2,3-b]indole Derivatives as Host Materials

摘要

Quantum efficiency is an important device performance parameter of phosphorescent organic light-emitting diodes (PHOLEDs), because it is critical to the power consumption of organic light-emitting diode panels. Therefore, there has been much effort to improve the quantum efficiency of PHOLEDs. High quantum efficiencies greater than 20% have been achieved in red, green, and blue PHOLEDs by developing new materials and device architectures. High-triplet-energy host materials have contributed to the high quantum efficiency of PHOLEDs, because holes and electrons balance in the emitting layer can be controlled mainly by the host materials. Many triplet host materials have been developed to obtain high quantum efficiency in PHOLEDs, among which bipolar host materials have been the most effective.'5"15' In general, the bipolar host materials have a molecular structure made up of a hole transport unit and an electron transport unit to balance the hole and electron transport properties in the emitting layer. Carbazole has been used as a hole transport unit, while pyridine,'1113' phosphine oxide, and oxa-zole have typically been used as electron transport units.