Indium oxide film transparent conductors

The geometry we use is shown in Fig. 20a. A semitransparent conductor, a photoconductor, a second semitransparent conductor, and a polymer film are successively deposited on a glass substrate. The semitransparent conductors are about 10-nm-thick layers of Nb deposited by ion-beam sputtering. Although the films have an optical density of—0.25, they are very stable and easy to contact. More transparent conductors, such as indium-tin-oxide, can be used if the subsequent processing temperature remains below 250°C. 

Transparent conductive coatings combine high optical transmission with good electrical conductivity. The existence of both properties in the same material is, from the physics point of view, not trivial and is only possible with certain semi-conductors like indium oxide, tin oxide, cadmium oxide, and with thin gold and silver films, e.g. [157]. Particularly antimony or fluorine doped tin oxide (ATO, FTO), tin doped indium oxide (ITO), and aluminium, indium, or boron doped zinc oxide (AZO, IZO, BZO) are of technical importance [157a]. 

At the same time, SWNT can be used at the top electrode (that needs to be transparent) as a replacement for the currently used thin films that are also electrical conductors. Typical conductive thin films used today are oxides such as fluorine-doped tin oxide (FTO), Al-doped zinc oxide, and the indium tin oxide (ITO) mentioned above. The disadvantages of these oxide films are that they require expensive deposition procedures at high vacuum, they have poor mechanical properties, and they are not transparent in the infrared. Another interesting difference is that transparent oxide conductors are n-type semiconductors. By contrast, nanotube networks act as p-type semiconductors, which could lead to new designs. 

Originally, a donor-acceptor bilayer device of two films was used as an n-p junction in solar cells. Thus, they were fabricated as sandwich structures. An example would be one where a transparent substrate is first coated with a conductor, like indium-tin oxide. A conducting polymer like, poly (ethylene dioxythiphene), doped with polystyrene-sulfonic acid, would then be applied from and aqueous solution. The indium-tin oxide acts as an electrode for hole injection or extraction. The polymer is then covered with a conductor, an aluminum foil. The doped polymer can be illustrated as follows ... 

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