Article published on www.sciencedaily.com July 20, 2012
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.
Study
authors also include Weiss; materials science and engineering postdoctoral
researcher Rui Zhu; Ph.D. candidates Chun-Chao Chen, Letian Dou, Choong-Heui
Chung, Tze-Bin Song and Steve Hawks; Gang Li, who is former vice president of
engineering for Solarmer Energy, Inc., a startup from UCLA; and CNSI
postdoctoral researcher Yue Bing Zheng
Transparent cells on water? Discover our floating solar systems on www.ciel-et-terre.net/floating-solar-system/