Tris-(8-hydroxyquinoline)aluminum-modified indium tin oxide for enhancing the efficiency and reliability of organic light-emitting devices

Tris-(8-hydroxyquinoline)aluminum (Alq(3)), which is typically used as an electron transport material for organic light-emitting devices (OLEDs), was used in this study for OLED anode modification. The electronic structure at the indium tin oxide (ITO)/organic interface for improvement of carrier injection was studied using ultraviolet photoelectron spectroscopy. The interfacial analysis reveals that the barrier height at the ITO/organic interface can be varied from similar to0.6-1.08 eV. It is demonstrated that the barrier for hole injection from an ITO anode to a hole transporting layer can be engineered by inserting an ultrathin interlayer of Alq(3), a few nanometers thick. The presence of an Alq(3) interlayer is shown to improve the current balance, leading to an enhancement in the electroluminecent efficiency and operational stability of OLEDs. (C) 2004 American Institute of Physics.