UCLA researchers have developed a new transparent solar cell that is an
advance toward giving windows in homes and other buildings the ability to
generate electricity while still allowing people to see outside. Their study
appears in the journal ACS Nano.
The UCLA team describes a new kind of polymer
solar cell (PSC) that produces energy by absorbing mainly infrared light, not
visible light, making the cells nearly 70% transparent to the human eye. They
made the device from a photoactive plastic that converts infrared light into an
electrical current.
"These results open the potential for
visibly transparent polymer solar cells as add-on components of portable
electronics, smart windows and building-integrated photovoltaics and in other
applications," said study leader Yang Yang, a UCLA professor of materials
science and engineering, who also is director of the Nano Renewable Energy
Center at California NanoSystems Institute (CNSI).
Yang added that there has been
intense world-wide interest in so-called polymer solar cells. "Our new
PSCs are made from plastic-like materials and are lightweight and
flexible," he said. "More importantly, they can be produced in high
volume at low cost."
Polymer solar cells have
attracted great attention due to their advantages over competing solar cell
technologies. Scientists have also been intensely investigating PSCs for their
potential in making unique advances for broader applications. Several such
applications would be enabled by high-performance visibly transparent
photovoltaic (PV) devices, including building-integrated photovoltaics and
integrated PV chargers for portable electronics.
Previously, many attempts have
been made toward demonstrating visibly transparent or semitransparent PSCs.
However, these demonstrations often result in low visible light transparency
and/or low device efficiency because suitable polymeric PV materials and
efficient transparent conductors were not well deployed in device design and
fabrication.
A team of UCLA researchers from
the California NanoSystems Institute, the UCLA Henry Samueli School of
Engineering and Applied Science and UCLA's Department of Chemistry and
Biochemistry have demonstrated high-performance, solution-processed, visibly
transparent polymer solar cells through the incorporation of near-infrared
light-sensitive polymer and using silver nanowire composite films as the top
transparent electrode. The near-infrared photoactive polymer absorbs more
near-infrared light but is less sensitive to visible light, balancing solar
cell performance and transparency in the visible wavelength region.
Another breakthrough is the
transparent conductor made of a mixture of silver nanowire and titanium dioxide
nanoparticles, which was able to replace the opaque metal electrode used in the
past. This composite electrode also allows the solar cells to be fabricated
economically by solution processing. With this combination, 4% power-conversion
efficiency for solution-processed and visibly transparent polymer solar cells
has been achieved.
"We are excited by this new
invention on transparent solar cells, which applied our recent advances in
transparent conducting windows (also published in ACS Nano) to fabricate these
devices," said Paul S.Weiss, CNSI director and Fred Kavli Chair in
NanoSystems Sciences.
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