Researchers at the Georgia Institute of Technology
have made a three-dimensional photovoltaic cell around an optical
fibre.
The conversion structure is dye-sensitised and is based on
coated zinc oxide structures grown on the fibre.
"Using this technology, we can make photovoltaic generators that
are foldable, concealed and mobile," said
Professor Zhong
Lin Wang. "Optical fibre could conduct sunlight into a
building's walls where the nanostructures would convert it to
electricity. This is truly a three dimensional solar cell."
The fibre, with cladding removed, is covered with a conductive
layer and seeded with ZnO.
Aligned zinc nanowires are then grown around the fibre from
solution, making something that looks like a bottle brush.
The wires are coated with appropriate dye, and then immersed in
a liquid electrolyte to complete the circuit.
Efficiency of 3.3% is claimed.
"In each reflection within the fibre, the light has the
opportunity to interact with the nanostructures that are coated
with the dye molecules," Wang explained. "You have multiple light
reflections within the fibre, and multiple reflections within the
nanostructures. These interactions increase the likelihood that the
light will interact with the dye molecules, and that increases the
efficiency."
Wang and his research team, which includes Benjamin Weintraub
and Yaguang Wei, have produced photo-generators on optical fibre up
to 20cm long.
"The longer the better," said Wang, "because the longer the
light can travel along the fibre, the more bounces it will make and
more it will be absorbed."
Improvements including a better method for collecting charges
and a titanium oxide surface coating could increase efficiency to
7-8%, said the University.
Wang is also looking at replacing the traditional quartz optical
fibre with cheaper polymer fibre.
Georgia Tech Regents professor Zhong Lin Wang holds a
prototype three-dimensional solar cell that could allow PV systems
to be located away from rooftops.