Transparent electrode for oleds

The thin films of transparent conducting oxides (TCOs) have widespread applications owing to their unique properties of good electric conductivity and high optical transparency in the visible spectrum range. There has been a great deal of activities in the development of TCOs for a variety of applications. In general, properly doped oxide materials, e.g., ZnO, SnO2, and In2O3, are used individually or in separate layers, or as mixtures such as indium-tin oxide (ITO) and indium-zinc oxide (IZO) for making TCO thin films. ITO, 588aluminum-doped ZnO (AZO), and fluorine-doped SnO2 (FTO) are commonly used TCO materials for different applications. The distinctive characteristics of these TCOs have been widely used in antistatic coatings, heat mirrors, solar cells [1,2], flat-panel displays [3], sensors [4], and organic light-emitting diodes (OLEDs) [5-7]. The properties of TCO films are often optimized accordingly to meet the requirements in the various applications that involve TCO. A light-scattering effect due to the use of textured TCO substrates helps enhance light absorbance in thin-film amorphous silicon solar cells [8,9]. However, a rough TCO surface is detrimental for OLED applications. The localized high electric fields induced by the rough TCO surface can cause a nonuniform current flow, leading to dark spot formation or a short device operation lifetime.