Effect of a plasma treatment of ITO on the performance of organic electroluminescent devices

We investigated the effect of plasma treatments of indium-tin oxide (ITO) surface on the performance of electroluminescent (EL) devices using different gases. In the case of air or argon, an intense EL emission was observed at low applied voltages. On the other hand, when hydrogen was used, very high voltages were needed to obtain the EL emission. The change in voltage was attributed to the removal of contaminants and to the change in work function of ITO. For the devices with the ITO treated with hydrogen plasma, the EL efficiency was very low. This result suggested that electrons accumulated at the organic/organic interface exert a harmful effect on the light emission.