Effect of waiting time of indium tin oxide electrode in entry chamber on organic light-emitting diodes

To obtain efficient organic light-emitting diodes (OLEDs), the degradation in the surface properties of the indium tin oxide (ITO) electrode during the device fabrication should be prevented. In this study, we investigated the effect of the waiting time of ITO in the entry chamber before the transfer to the deposition chamber on the device performances of OLEDs. The current density and luminance of the OLED significantly decreased owing to the reduced hole injection with the increase in the waiting time. The origin of the reduced hole injection was estimated to be (1) the formation of trap sites at the interface between ITO and hole-transport layer and (2) decreased work function of ITO by an interface dipole. These phenomena could be attributed to the contamination of the ITO surface by the waiting under a relatively low vacuum and room light illumination.