News in Science

Solar cells get silver lining

better solar cells Light-trapping, silver nano-antennas could dramatically improve the performance of solar panels by catching more light, according to a new study.

A team of physicists, including Professor Constantin Simovski from Finland's Aalto University, has developed theoretical designs that could increase photovoltaic cell efficiency in a commercially viable way.

It proposes incorporating chessboard-patterned arrays of tiny silver nano-antennas into solar panels.

This would trap more incoming light, allowing it to be preferentially re-radiated through the photovoltaic slab, improving efficiency.

New fabrication techniques for printing a nano-antenna array on thin film means it could be done at low cost.

"Pieces of the film with printed nano-antenna arrays can be prepared separately from solar cells so that the price of every piece will be small," report the researchers on the pre-press website ArXiv.org.

"We have demonstrated our nano-antenna arrays operate significantly better than the structures based on anti-reflecting coatings."

Existing technology uses coatings to reduce the amount of light reflected off the solar cell, but this fails to prevent up to half of the light passing through the back of the solar cell's thin film and being lost.

The best currently available commercial photovoltaic cells convert just 22 per cent of the light they receive into electricity, according to the researchers, who also say that this level can be improved with existing technology, but the cost is prohibitive.

Like minds

Dr Richard Corkish, Head, School of Photovoltaic & Renewable Energy Engineering at the University of New South Wales, says Australian research is following a similar approach.

"Our work together with researchers at the Australian National University and Swinburne University, use self-aligning, nano-scale, metal-silver particles that act like nano-antennas redirecting the light," says Corkish.

"The difference is our research uses randomly shaped and positioned particles, while this paper discusses very precisely formed and aligned antennas."

While this precise alignment will be more efficient, Corkish thinks it will also be far more expensive.

"They're looking for a low-cost approach, while our approach is even more low cost because of the more random nature of the antenna positioning and shapes."

Corkish says his team has managed to get its solar cells performing at 25 per cent efficiency in the lab, however the cost of producing such cells is still prohibitive for industry.

"The trick is to get something really cheaply that works and can cover big areas," says Corkish.

"They talk about printing big sheets of this material at very low cost and if they can do that, it would be very interesting."