Effect of ultraviolet-ozone treatment of indium-tin-oxide on electrical properties of organic light emitting diodes

We report the change of surface electronic structure of indium-tin-oxide (ITO) as a function of ultraviolet (UV)-ozone treatment time. The voltage of organic light emitting diodes at a current density of 100 mA/cm(2) was reduced as the surface treatment time using UV-ozone was lengthened. X-ray photoelectron spectroscopy results showed that the relative concentration of carbon atoms decreased, but oxygen concentration increased relatively with UV-ozone treatment. This led to the increase in the ITO work function via the reduction of operation voltage. (C) 2004 American Institute of Physics.