The surface properties of treated ITO substrates effect on the performance of OLEDs

Surface modification was performed on the indium-tin-oxide (ITO) substrates for organic light-emitting diodes (OLEDs) by oxygen plasma. The effects of oxygen plasma treatment on the surface properties of ITO substrates and its aging were investigated by the measurements of the chemical composition, contact angle and surface energy. We observe that oxygen plasma treatment improves the stoichiometry of the surface and enhances ITO wetting, so as to improve the surface properties of ITO substrates. With the increment of storage time, however, the improved ITO surface properties tend to decay and the surface energy decreases. Furthermore, we studied the effect of aging variation of surface properties of treated ITO substrates on the performance of OLEDs, in terms of driving voltage, luminance, and efficiency. The device performance of the OLEDs was found to become worse with the increasing storage time after oxygen plasma on ITO substrates. The results demonstrate that the device performance of the OLEDs strongly depends on the surface properties of the ITO substrates