An antireflective film inspired by moth's eyes has been
shown to improve the efficiency of solar cells (Photo: Olaf
Leillinger)
In order for a solar cell to be as efficient as possible, the
last thing it should be is reflective – after all, light should
be getting absorbed by it, not being bounced off. With that in
mind, a few years ago a group of Japanese scientists set out to
create an antireflective film coating for use on solar cells.
What they ended up creating utilizes the same principles that
are at work in one of nature’s least reflective surfaces: moth’s
eyes.
The moth-eye film was developed by Noboru Yamada, a scientist
at
Nagaoka University of Technology Japan, who collaborated
with researchers at
Mitsubishi Rayon Co. Ltd. and
Tokyo Metropolitan University. Using anodic porous alumina
molds, they were able to nanoimprint the microstructure of
moth’s eyes into acrylic resin – this provided a high
throughput, large-area/low-cost method of producing the film.
Based on the results of indoor and outdoor tests of
crystalline silicon solar panels coated with the film, the
team’s computer models indicated that use of the film could
boost the annual efficiency of solar cells by five percent in
Tokyo, and six percent in the “sun belt” city of Phoenix.
“People may think this improvement is very small, but the
efficiency of photovoltaics is just like fuel consumption rates
of road vehicles,” said Yamada. “Every little bit helps.”
They are now working on improving the durability of the film,
and optimizing it for use on different types of solar cells.
They are also looking into using it to reduce glare on surfaces
such as windows and computer screens, although in that area they
may be facing some competition – Germany’s
Fraunhofer Institute for Mechanics of Materials has already
developed an anti-reflective coating for use on displays and
eyeglasses, which was also inspired by moth’s eyes. In
Franuhofer’s case, the coating is incorporated into the viewing
surface during the molding process, instead of being added
afterward in the form of a film.
The reasons that moths have anti-reflective eyes,
incidentally, is to allow them to gather as much light as
possible in the dark, and to avoid being seen by predators.
The moth-eye film research was recently published in the
journal
Energy Express.
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