We report the enhancement of electron injection using an Al-Mg alloy cathode in organic light emitting diodes (OLEDs). The luminescence value at 15 V drastically increased from 800 to 5800 cd/m(2) as the Al cathode was replaced by an Al-Mg alloy with a 1:1 ratio of Al to Mg in weight percent. Synchrotron radiation photoelectron spectroscopy results showed that the work function of the Al-Mg alloy is lower by 0.2 eV than that of Al. Thus, the energy barrier for electron injection was lowered, reducing the turn-on voltage and increasing the quantum efficiency of OLEDs. (c) 2005 The Electrochemical Society. [DOI: 10.1149/1.2135426] All rights reserved.