High-Efficiency and Long Lifetime Electrophosphorescent Organic Light-Emitting Diodes with Improved Hole-Electron Balance by using Alternate Multilayer Structures

摘要

Electrophosphorescent organic light-emitting diodes (PHOLEDs) owith alternate multilayer structures, which consist of N,N'-bis-(l-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (NPB) and 5,6,11,12-tetraphenylnaphthacene (rubrene) as hole-transporting layers have been fabricated. The effect of the alternate multilayer structures upon ther performance of PHOLEDs with fac-tris(2-phenylpyridine)iridium (Ir(ppy)3) doped into 4,4'-N,N'-dicarbazole-biphenyl (CBP) as the emitting layer has been investigated. Compared with the conventional diode only with NPB as hole-transporting layer, high efficiency and long lifetime diodes have been obtained with the alternate structures. Such an improvement in the device performance -was attributed to the improved hole-electron balance, which can be further attributed to the introduction of the alternate multilayer structure into PHOLEDs.