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 $\text{100\hspace{0.17em}}{\mathrm{mA/cm}}^2$ 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.