Jun 21, 2011
Spray process applies silver nanowire network to plastic, glass and fabric
Doped-metal oxides such as tin-doped indium oxide (ITO) have been the primary choice for making transparent conductive electrodes on an industrial scale. But the rising cost of indium, the poor flexibility of ITO and the requirement for high processing temperatures are motivating developers to find new electrode materials for flexible optoelectronic device applications. One potential candidate is silver nanowire.
Researchers at the University of Southern California, US, are exploiting the high conductivity of silver, the percolation behaviour of nanowire networks and well established spray coating technology, to develop highly conductive silver nanowire films on arbitrary substrates (plastic, glass and fabric).
Using a polydimethylsiloxane (PDMS)-assisted contact transfer technique, the team has demonstrated scalable patterned films that are highly flexible.
To make the components, silver nanowire solution is sprayed on the substrate of interest. Spray conditions, such as the compressed air pressure, the distance between the nozzle and substrate, and the nozzle diameter are optimized to obtain a uniform silver nanowire film. The transparency and conductivity of the films is controlled by the volume of the dispersion used for spraying and the substrate area.
The optoelectrical property, σDC/σOp, of the various fabricated films was found to be in the range 75–350, which is extremely high for transparent thin film compared with other alternatives to doped metal oxide film.
Silver nanowire films formed on a flexible polyethylene terephthalate (PET) substrate using this method were shown to have a sheet resistance of 33 Ω/sq at a transparency value of 85%, which is comparable to currently used tin-doped indium oxide (ITO) on flexible substrates.
The films also posses extremely good mechanical flexibility and the researchers have demonstrated a prototype touch screen based on the silver nanowire technology.
The group believes that silver nanowire films are emerging as a strong candidate to replace ITO in next generation transparent conductive electrodes with applications in optoelectronic devices and smart fabric.
The researchers presented their work in the journal Nanotechnology.
About the author
Anuj Rahul Madaria is currently pursuing his PhD in Chongwu Zhou's group at the University of Southern California, Los Angeles, California, US. He is currently exploring synthesis, assembly and application of various metallic and semiconducting nanowires.