Enhancement of optical properties in organic light emitting diodes using the Mg-Al alloy cathode and IrOx-coated indium tin oxide anode

Abstract

We report the enhancement of quantum efficiency using the Mg-Al alloy cathode and IrOx-coated indium tin oxide (ITO) anode in organic light emitting diodes (OLEDs). The external quantum efficiency at the current density of 64 mA/cm(2) increased from 0.04% to 1.89% as the Al cathode and ITO anode changed to the Mg-Al cathode and IrOx-coated ITO anode, respectively. Synchrotron radiation photoelectron spectroscopy results show that the work function of IrOx-coated ITO is higher by 0.5 eV than that of the ITO and the work function of the Mg-Al alloy is lower by 0.2 eV than that of Al. Thus, both the hole and electron injection energy barriers were simultaneously lowered, reducing the turn-on voltage and increasing the quantum efficiency of OLEDs. (c) 2006 American Institute of Physics.