X-ray photoelectron spectroscopy of surface-treated indium-tin oxide thin films

Angle-resolved X-ray photoelectron spectroscopy and photothermal deflection spectroscopy are used to study the oxygen-plasma or aquaregia treated indium-tin oxide (ITO) anodes for organic light-emitting diodes. Detailed analysis of the O1s core-level spectra and their dependence on photoemission angle was performed. The results indicate the presence of different chemical forms of oxygen atoms (two types of O2−, OH−, organic oxygens and H2O) which evolve with surface treatment. We find that the treatments lead to a modification of the surface chemical states and therefore of the physico-chemical properties of ITO, which in turn control the performance of organic light-emitting diodes.