|Carbon nanotube solar cells point to possible transparent solar window future
Imagine if every window of the 828-meter (2,717-foot) high Burj Khalifa in Dubai was capable of generating electricity just like a PV panel. Thatís the promise of solar window technology like the RSi and Sphelar cells
systems. Rather than using costly silicon for window-based collection
of solar energy, Dr Mark Bissett proposes using a very thin layer of
carbon nanotubes instead.
As part of his PhD at the Flinders University School of Chemical and
Physical Sciences, Dr Bissett has developed a proof of concept prototype
solar cell that is made up of two sheets of electrically-conductive
glass with a layer of functionalized, single-walled carbon nanotubes
sandwiched between them. As the nanotube layer is only between 100 -
200nm thick and the two sheets of glass are just 60Ķm apart, the cell
remains transparent - letting some natural light flow through while also
collecting energy from the sun.
"When light shines on the cell, electrons are generated within the
carbon nanotubes and these can be used to power electrical devices,"
said Dr Bissett. "Itís basically like tinting the windows except theyíre
able to produce electricity, and considering office buildings donít
have a lot of roof space for solar panels, it makes sense to utilize the
many windows they do have instead."
Unfortunately, the cells have yet to be tested outside of the
laboratory and work is still needed to improve the efficiency of the
technology before being scaled up to an industrial level. Dr Bissett
told us that the trade-off between transparency and the ability to
harvest light means that even the best cells in the lab are only just
approaching 1% efficiency. There is a way around this, but it comes at a
"Basically by decreasing transparency you can increase efficiency,"
explained Dr Bissett. "In comparison, other new solar cell technologies
like dye-sensitized solar cells are close to 10% and silicon solar cells
tend to be around the 20% mark, depending on the exact technology used
to produce them. So work is still needed on increasing the efficiency of
our designs to make them competitive, but it is still early days for
this technology with many possible research avenues to pursue."
Dr Bissett has also successfully demonstrated that the carbon
nanotube layer can be spray-coated onto glass, which would allow for
larger areas of glass substrate to be functionalized. The next step in
the development process is to test the technology in the real world. He
believes that if all goes to plan, the new technology could be on the
market within the next ten years.
"This research is still being pursued by the research group I worked
with at Flinders University with Professor Joe Shapter," he said. "There
is also work being undertaken to produce flexible solar cells based on
graphene, these are of interest for integration into fabrics."
Meanwhile Dr Bissett is currently undertaking a post-doctorate at Kyushu University, Japan.
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