Solar cells spring from
SOLAR CELLS ARE NO LONGER confined to flat
panels, thanks to a new technique that turns optical
fibers into long, thin solar cells.
By assembling the components of a dye-sensitized
solar cell along the outside of an optical cable,
Georgia Institute of Technology researchers were
able to demonstrate thin, flexible solar cells that
are six times more efficient than flat panels using
the same materials.
“We face the fiber’s end directly at the sun,” said
Georgia Tech professor Zhong Lin Wang. “There is
an electrode located next to the fiber that collects
the generated charge, which is connected to the
Wang performed the work with Georgia Tech
researchers Benjamin Weintraub and Yaguang Wei.
Dye-sensitized solar cells were invented in the
1990s as a thin-film version of photovoltaics. Whereas
silicon solar cells use expensive semiconductor
materials to generate a charge, researchers created
dye-sensitized solar cells by substituting an inexpensive
thin film of dye molecules atop zinc oxide
nanowires in an electrolyte surrounded by a metal
film. When light shines on the dye cells, they shed
their electrons into the metal film, which transports
them to the external electrode.
One problem with conventional solar panels is that incident
photons have little chance of energizing electrons in the
thin panels before degenerating into heat. By contrast, optical
fibers give photons many more chances to interact with the
The Georgia Tech prototype used fibers 20 cm long to
ensure that most photons were absorbed somewhere along
the fiber’s length.
The technique collects sunlight at the tips of the optical
fibers, then channels the light down the length of the fibers.
Future versions may use a transparent outer metallic sheath,
thereby allowing light to enter from both inside and outside.
The Georgia Tech researchers also want to create bundled
subsystems that would consist of of hundreds of parallel
fiber optical cables.
Meanwhile, efficiency must be increased, from 3.3 percent
to as much as 8 percent, in order to commercialize the technology,
the researchers said.
Wang said he also plans to experiment with cheaper optical
fiber materials to reduce costs, while substituting titanium
oxide for zinc oxide to boost efficiency.
For commercial systems, designers might use the fibers to
create nontraditional shapes beyond flat panels. For military
applications, the fibers could be built into equipment to produce
Funding for the solar research was provided by the Defense
Advanced Research Projects Agency, the King Abdullah University
of Science and Technology Global Research Partnership
and the National Science Foundation. p