Organic semiconductor heterojunction and its application in organic light-emitting diodes (Conference Presentation)

Abstract

Organic light-emitting diodes (OLEDs) have drawn increasing attention as the next generation displays and lighting sources. High efficiency and long lifetime are necessary for OLEDs in practical applications. In conventional OLEDs, the charge carriers are directly injected into the organic transport layers from electrodes, the injection barriers between the organic transport layers and electrodes are unavoidable due to the mismatch between the work function of metal electrode and the energy level of charge-transport layer, which greatly affects the performance of fabricated OLEDs. Furthermore, tandem OLEDs, which are fabricated by vertically connecting several individual electroluminescent (EL) units together in series via an appropriate charge generation layer (CGL) with the entire device driven by a single power source can significantly enhance current efficiency and stability, but their performance is strongly dependent on the used CGL, especially the power efficiency is difficult to enhance due to the increase of working voltage. Recently we found that organic semiconductor heterojunctions show efficient charge generation effect and as CGL, not only double the luminance and current efficiency, but also greatly improve the power efficiency, which is difficult in tandem OLEDs based on conventional CGLs. We also realized electrode-independent charge injection by using organic semiconductor heterojuncrions as injectors in OLEDs, and obtained comparable electroluminescent (EL) performance with that of conventional OLEDs. Here, we report the results of tandem OLEDs based on organic semiconductor heterojunctions as CGL and OLEDs using organic semiconductor heterojunctions as injectors, and discuss this working mechanism in detail.