The Work Function Improvement on Indium−Tin−Oxide Epitaxial Layers by Doping Treatment for Organic Light-Emitting Device Applications

In this paper, we present an approach to coating the thin high work function (HWF, with q φ m in eV) films on an indium tin oxide (ITO)/glass substrate. Thin HWF films are co-sputtered on an ITO using the vanadium (V +4 ion) dopant concentrations from 0% to 12.25%, and the q φ m values are increased from 4.80 to 5.25 eV, respectively. The HWF−ITO deposition condition is developed for organic light-emitting device (OLED) applications. The electro-luminescence (EL) improvement, in particular the turn-on voltage from 7.7 to 0.3 V, is well correlated with the work function change. The output luminance (in cd/m 2 ) at 10 V driving voltage of the developed OLED is increased from 35 K cd m -2 (at 5% V +4 -ion concentrations) to 75 K cd m -2 (at 5% V +4 -ion concentrations). These EL results with the HWF−ITO film are well above the OLED application standard.