TWI Industrial Member Report Summary 829/2005
By A Gunner, A Taylor, P Jackson and J S Abell*
The highest value market for Transparent Conductive Coatings (TCCs) is in flat panel displays, with a closely related application in thin film solar cells. The electrical properties of TCCs are exploited for transparent heaters, found in applications such as heated windscreens and in ruggedised LCD displays, capable of operating at low temperatures. Continuous TCC films are used for Electromagnetic Interference and Radio Frequency Interference (EMI/RFI) shielding and as anti-static coatings. The spectral response characteristics of TCCs are exploited for glazing (climate control) applications, which currently represent their largest volume market.
TCCs are commonly based on transparent, semiconducting materials with a wide band gap. These can then be doped to give the desired electrical properties. Antimony tin oxide (ATO) and Indium tin oxide (ITO) are the most commonly used materials.
The final properties of a TCC are strongly dependent on the preparation method. Commercial manufacture is currently limited to CVD for low grade, bulk coatings and sputter coating for high specification materials, mainly ITO. Being a vacuum method, sputter coating has limitations, hence solution based methods for fabricating TCCs have received considerable interest over recent years.
The purpose of this project was to demonstrate the capability of fabricating a transparent conducting coating via a solution synthesis (sol-gel) route. The coating composition selected for study was indium tin oxide, since this is the most commonly used TCC and a range of fabrication procedures has been reported.
- To deposit sol-gel derived ITO coatings on glass and characterise them in terms of microstructure and electrical resistance.