Indium-Free Alternative Transparent Conducting Electrodes: An Overview and Recent Developments

Abstract

The cost and demand of indium tin oxide (ITO) electrodes are high due to extensive usage in modern gadgets. Presently the industry is facing the problem of scarcity of indium, which has led to increased exploration of alternate materials for replacing indium-based transparent conducting oxide electrodes (TCOs). Hence, devel- opment of highly efficient and cost-effective transparent conducting electrodes (TCEs) to meet out the demand is the need of the hour. This chapter first gives a brief outline of the market analysis on the availability of indium and also the status of alternate materials that are currently competing in the market. This is followed by a brief overview of various materials that are explored for TCE applications such as metal nanowires, carbon nanotubes, graphene, binary/multi-component oxide systems, etc. The general properties ofa material that are desired for serving as an TCE are also dealt in sufficient detail. Among the oxide-based TCEs, binary metal oxides possess good electrical and optical properties and are easy for doping with a variety of donor elements. Importantly, the AO2 binary rutile structure of SnO2 offers high flexibility to incorporate dopants at the “A” site leading to tuning of bandgap and surface work function. In view of this flexibility, we have portrayed important results ofSnO2 doped with donor elements like Sb, Sb-Ba (co-doping), Nb, and Ta by the facile and cost- effective spray pyrolysis method. The structural, surface morphology, optical, electri- cal, and temperature stability of sheet resistance of these films are discussed.