Surface treatments of indium‐tin oxide substrates for polymer electroluminescent devices

Abstract

Abstract In this work, three different sets of processing techniques (wet, dry, and combined treatments) were utilized to modify the surfaces of indium‐tin oxide (ITO) substrates for polymer electroluminescent devices (PELDs), and the influence of surface treatments on the surface properties of ITO substrates were investigated by X‐ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), contact angle, and four‐point probe. The surface energies of ITO substrates were also calculated from the measured contact angles. Experimental results show that the surface properties of the ITO substrates strongly depend on the surface treatments. Oxygen plasma treatment effectively improves the ITO surface properties since plasma decreases the surface roughness and sheet resistance, improves the surface stoichiometry and wetting. Furthermore, the PELDs with the differently treated ITO substrates as hole‐injecting electrodes were fabricated and characterized. We observe that the optical and electrical characteristics of devices are greatly influenced by the surface treatments on ITO substrates. Oxygen plasma treatment decreases turn‐on voltage, increases brightness and efficiency, and thereby improves the device performance of PELDs. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)