Zinc oxide based transparent electrodes for flexible thin film devices
Transparent electrodes are an important component for various thin film devices. The paper will present a review of present solutions covering single layer conducting oxides as well as composite technologies. Special emphasis will be put on the mechanical stability of the electrode on plastic film. Conventional indium tin oxide (ITO) layers break at a stretching of 1-2%. The mechanical sensitivity of the samples increases with increasing thickness. This requires new solutions for low sheet resistance electrodes on flexible substrates. A novel cost effective technology for the deposition of zinc oxide on polyethylene terephtalate film is presented. The deposition was performed in a roll-to-roll coating machine at low substrate temperature. Silicon was used as the dopant material with a concentration varying in different samples between 1 and 4%. The optimum parameters provided a transparent layer with a sheet resistance of 16 ? sq. The carrier density and the mobility were determined by Hall measurements. They amounted to 8.8 cm² V-1s-1 and 2.5x1020 cm-3, respectively. These values are a promising starting point for the deposition on heat sensitive substrates.