Transparent conducting film

Transparent conducting films (TCFs) are thin films of optically transparent and electrically conductive material. They are an important component in a number of electronic devices including liquid-crystal displays, OLEDs, touchscreens and photovoltaics. While indium tin oxide (ITO) is the most widely used, alternatives include wider-spectrum transparent conductive oxides (TCOs), conductive polymers, metal grids and random metallic networks, carbon nanotubes (CNT), graphene, nanowire meshes and ultra thin metal films. TCFs for photovoltaic applications have been fabricated from both inorganic and organic materials. Inorganic films typically are made up of a layer of transparent conducting oxide (TCO), most commonly indium tin oxide (ITO), fluorine doped tin oxide (FTO), niobium doped anatase TiO2 (NTO) or doped zinc oxide. Organic films are being developed using carbon nanotube networks and graphene, which can be fabricated to be highly transparent to infrared light, along with networks of polymers such as poly(3,4-ethylenedioxythiophene) and its derivatives. Transparent conducting films are typically used as electrodes when a situation calls for low resistance electrical contacts without blocking light (e.g. LEDs, photovoltaics). Transparent materials possess wide bandgaps whose energy value is greater than those of visible light. As such, photons with energies below the bandgap value are not absorbed by these materials and visible light passes through. Some applications, such as solar cells, often require a wider range of transparency beyond visible light to make efficient use of the full solar spectrum. Transparent conductive oxides (TCO) are doped metal oxides used in optoelectronic devices such as flat panel displays and photovoltaics (including inorganic devices, organic devices, and dye-sensitized solar cells). Most of these films are fabricated with polycrystalline or amorphous microstructures. Typically, these applications use electrode materials that have greater than 80% transmittance of incident light as well as electrical conductivities higher than 103 S/cm for efficient carrier transport.