Thin metallic oxides as transparent conductors

Films of tin oxide doped with fluorine or of indium oxide doped with tin (i.e. indium tin oxide (ITO)) can be obtained by standard procedures such as thermal evaporation or sputtering, or by other methods such as the hydrolysis of metallic chlorides (spraying) or the pyrolysis of organometallic compounds (chemical vapour deposition). The optical and electrical properties of these layers are very similar: for thicknesses in the range of a few hundred nanometers, a resistivity ? of the order of 4 × 10^?4 Ω cm and a transparency T of 80%–90% in the visible range of the spectrum are obtained. These layers are commonly used as transparent heating systems and in the field of digital display and light-emitting devices. More recently, some large-scale uses have been envisaged in the field of solar energy. Solar cells with a conversion efficiency of 12% have been obtained for ITO/Si or SnO₂/Si structures. Stack filters such as glass/SnO₂:F/(black molybdenum)/SnO₂:F have shown excellent properties as photothermal converters.