Researchers in the Department of Chemistry at the University of Warwick have found out a new method to pattern metals, which could render the next generation of solar panels cheaper and more sustainable.
The most extensively employed electrical conductors in modern electronics and solar cells are silver and copper. However, traditional techniques of patterning these metals to create the required pattern of conducting lines are based on selectively eliminating metal from a film by etching with toxic chemicals or printing from expensive metal inks.
Researchers from the Department of Chemistry at the University of Warwick have created a method for patterning these metals that is expected to prove much more sustainable and cheaper for large-scale production. This is because there is no metal waste or use of toxic chemicals, and the fabrication technique is compatible with continuous roll-to-roll processing.
The research has been described in the paper titled “Selective deposition of silver and copper films by condensation coefficient modulation” published as an advanced article on 13th August 2019 in the journal Materials Horizons.
The £1.15 M funding from the UK Engineering and Physical Sciences Research Council has helped Dr Ross Hatton and Dr Silvia Varagnolo to discover that silver and copper do not condense onto very thin films of some highly fluorinated organic compounds upon depositing the metal by simple thermal evaporation.
Thermal evaporation is already extensively used on a large scale to form the thin metal film on the interior of crisp packets, and organofluorine compounds are already in use as the base of non-stick cooking pans.
The scientists have proven that the organofluorine layer has to be just 10-billionths of a meter thick to be effective, and hence only small amounts are required.
Furthermore, this innovative method does not contaminate the metal surface, which Hatton thinks will be specifically vital for the next generation sensors that usually need uncontaminated patterned films of these metals as platforms onto which sensing molecules can be secured.
To help tackle the problems created by climate change, there is a need for flexible, color-tunable, and lightweight solar cells that can be formed at low cost, especially for applications where traditional rigid silicon solar cells are inappropriate, for example, in electric cars and semi-transparent solar cells for buildings.
Solar cells based on thin films of organic, perovskite, or nano-crystal semiconductors all have the capability to meet this requirement, while they all need a low-cost, flexible transparent electrode.
Hatton and his group have used their technique to make semi-transparent organic solar cells where the top silver electrode is patterned with millions of tiny apertures per square centimeter, which cannot be realized by any other scalable method directly on top of an organic electronic device.
This innovation enables us to realize 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.
Dr Hatton, Department of Chemistry, University of Warwick