Researchers at the University of Warwick have developed a new way of making patterned films of silver and copper. It could make the manufacture of solar cells and electronics greener, faster and cheaper.
Silver and copper are widely used in electronic and solar cells, but patterning them to make the desired pattern of conductive lines requires the use of harmful chemicals or costly metal inks to etch or print them on to the surface.
A new technique developed at Warwick’s department of chemistry and described in the journal Material Horizons uses cheap organofluorine compounds. It doesn’t require the use of toxic chemicals or leave metal waste, and remains compatible with continuous roll-to-roll processing.
Ross Hatton and Silvia Varagnolo discovered that silver and copper do not condense onto extremely thin films of highly fluorinated organic compounds during simple thermal evaporation.
Thermal evaporation is already widely used on a large scale to make the thin metal film on the inside of crisp packets, and organofluorines are used as the basis of non-stick cooking pans.
The researchers found that only tiny amounts of organofluorines are needed for the technique to work, and that the approach leaves the rest of the metal uncontaminated. This could be particularly important for the next-generation sensors, which often require uncontaminated patterned films of these metals as platforms onto which sensing molecules can be attached.
The method has also been used to fabricate semi-transparent organic solar cells in which the top silver electrode is patterned with millions of tiny apertures per square centimetre, which cannot be achieved by any other scalable means directly on top of an organic electronic device. “This innovation enables us to realise the dream of truly flexible, transparent electrodes matched to needs of the emerging generation of thin-film solar cells, as well as having numerous other potential applications ranging from sensors to low-emissivity glass,” Hatton says.
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