Seeing is believing: a versatile new approach to optically transparent electrodes

Although materials having both excellent optical transparency and electrical conductivity at first seem counterintuitive, such substances are essential to a myriad of modern technologies. Applications for transparent conductors include electrodes for LCD, OLED and other displays, touch screens, electromagnetic interference shielding, transparent heaters (for example, automotive windshields), and photovoltaic cells.1 For many applications, mechanical flexibility, as on plastic substrates, is also desirable for versatile form factors, impact resistance, roll-to-roll manufacture, product functionality and light weight. For many applications, the oxides of heavy post-transition metals, such as tin-doped indium oxide (ITO) or, to a lesser extent, related oxides, have traditionally served this purpose.1 However, the cost of ITO is sensitive to fluctuating indium prices, electrical conductivity is not optimum, ITO is corroded in many environments, polycrystalline ITO coatings on plastic are brittle and less conductive, and ITO films are grown by capital-intensive sputtering processes.1 A key issue in vapor-phase coating processes is the percentage of material actually transferred to the substrate, and for ITO this process has been heavily optimized for high yields.