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.