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Special Coating Greatly Improves Solar Cell Performance; The Hot-Line Solar Coll
Posted on Saturday, February 23, 2008 @ 12:23:27 GMT by vlad
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The energy from sunlight falling on only 9 percent of California’s
Mojave Desert could power all of the United States’ electricity needs
if the energy could be efficiently harvested, according to some
estimates. Unfortunately, current-generation solar cell technologies
are too expensive and inefficient for wide-scale commercial
applications.
A team of Northwestern
University researchers has developed a new anode coating strategy that
significantly enhances the efficiency of solar energy power conversion.
A paper about the work, which focuses on “engineering” organic
material-electrode interfaces in bulk-heterojunction organic solar
cells, is published online this week in the Proceedings of the National Academy of Sciences. The PNAS
paper is titled “p-Type Semiconducting Nickel Oxide as an
Efficiency-enhancing Anode Interfacial Layer in Polymer
Bulk-heterojunction Solar Cells.”
This breakthrough in solar
energy conversion promises to bring researchers and developers
worldwide closer to the goal of producing cheaper, more manufacturable
and more easily implemented solar cells. Such technology would greatly
reduce our dependence on burning fossil fuels for electricity
production as well as reduce the combustion product: carbon dioxide, a
global warming greenhouse gas.
Tobin J. Marks, the Vladimir N. Ipatieff Research Professor in
Chemistry in the Weinberg College of Arts and Sciences and professor of
materials science and engineering, and Robert Chang, professor of
materials science and engineering in the McCormick School of
Engineering and Applied Science, led the research team. Other
Northwestern team members were researcher Bruce Buchholz and graduate
students Michael D. Irwin and Alexander W. Hains.
Of the new solar energy
conversion technologies on the horizon, solar cells fabricated from
plastic-like organic materials are attractive because they could be
printed cheaply and quickly by a process similar to printing a
newspaper (roll-to-roll processing).
To date, the most successful type of plastic photovoltaic cell is
called a “bulk-heterojunction cell.” This cell utilizes a layer
consisting of a mixture of a semiconducting polymer (an electron donor)
and a fullerene (an electron acceptor) sandwiched between two
electrodes -- one a transparent electrically conducting electrode (the
anode, which is usually a tin-doped indium oxide) and a metal (the
cathode), such as aluminum.
When light enters through the transparent conducting electrode and
strikes the light-absorbing polymer layer, electricity flows due to
formation of pairs of electrons and holes that separate and move to the
cathode and anode, respectively. These moving charges are the
electrical current (photocurrent) generated by the cell and are
collected by the two electrodes, assuming that each type of charge can
readily traverse the interface between the polymer-fullerene active
layer and the correct electrode to carry away the charge -- a
significant challenge.
The Northwestern researchers employed a laser deposition technique
that coats the anode with a very thin (5 to 10 nanometers thick) and
smooth layer of nickel oxide. This material is an excellent conductor
for extracting holes from the irradiated cell but, equally important,
is an efficient “blocker” which prevents misdirected electrons from
straying to the “wrong” electrode (the anode), which would compromise
the cell energy conversion efficiency.
In contrast to earlier approaches for anode coating, the
Northwestern nickel oxide coating is cheap, electrically homogeneous
and non-corrosive. In the case of model bulk-heterojunction cells, the
Northwestern team has increased the cell voltage by approximately 40
percent and the power conversion efficiency from approximately 3 to 4
percent to 5.2 to 5.6 percent.
The researchers currently are working on further tuning the anode
coating technique for increased hole extraction and electron blocking
efficiency and moving to production-scaling experiments on flexible
substrates.
Source: Northwestern University Via: http://www.physorg.com/news122908304.html ----------------
The Hot-Line Solar Collector
The Hot-Line module looks just about like a conventional flat-plate
collector. What makes Lightfoot's panel highly unconventional is that
it [1] contains a specially curved reflector which acts to concentrate
incoming sunlight on a wedge-shaped absorption tube, [2] operates with
an efficiency far surpassing that of any "normal" flat-plate solar
panel, and [3] actually "tracks" the sun through a 50 degree vertical
arc — and through 150 degrees in the east/west plane — without moving!
Dan Lightfoot came upon the idea for the Hot-Line collector quite by
accident a decade ago. It seems Dan had been observing a sheet of
aluminum that was resting up against his garage wall and noticed how
the sun's reflection from that curved sheet formed a bright spot on an
adjoining wall. Moreover, he noticed that the bright spot stayed in
roughly the same place throughout the day, despite the sun's constant
movement. This got Dan to thinking, and to experimenting. With the aid
of a small sheet of aluminum, a few scraps of wood and a handful of
bolts and clamps, Lightfoot found (by trial and error) that he could
curve the metal in such a way that it would focus light in a line — a
line that, furthermore, moved only a small distance in or out from the
metal as the jury-rigged reflector was tilted through various angles to
the sun. At this point, Dan knew that if he could just bend a long
sheet of reflective material to the same curvature, lay a channel along
the focal plane of the reflector thus created, and run air or water
through that channel, he'd have what no one had developed before: a
fixed-position, concentrating solar collector. (Focusing collectors are
nothing new, of course, but they all have one drawback: in order to
work, the reflector must face squarely into the sun at all times. This
usually calls, in turn, for a costly and complex motorized gimbal
mounting, to allow tracking of the sun. In contrast, Lightfoot's
collector can focus light all day long while remaining stationary. - Source Via: http://www.keelynet.com/#whatsnew
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Konarka Announces First-Ever Demonstration of Inkjet Printed Solar Cells (Score: 1) by vlad on Wednesday, March 05, 2008 @ 22:29:30 GMT (User Info | Send a Message) http://www.zpenergy.com | (Nanowerk News)
Konarka Technologies, Inc., an innovator in development and
commercialization of Power Plastic®, a material that converts light to
energy, today announced the company successfully conducted the
first-ever demonstration of manufacturing solar cells by highly
efficient inkjet printing. The company discusses and analyzes the
performance of highly efficient inkjet printed organic bulk
heterojunction solar cells in a paper recently published in Advanced
Materials, entitled, “High Photovoltaic Performance of Inkjet Printed
Polymer:Fullerene Blends” by Dr. Stelios A. Choulis, Claudia N. Hoth,
Dr. Pavel Schilinsky and Dr. Christoph J. Brabec, all of Konarka.
“Demonstrating the use of inkjet printing technology as a fabrication
tool for highly efficient solar cells and sensors with small area
requirements is a major milestone,” commented Rick Hess, president and
CEO at Konarka. “This essential breakthrough in the field of printed
solar cells positions Konarka as an emerging leader in printed
photovoltaics.”
Inkjet printing is a commonly used technique for controlled deposition
of solutions of functional materials in specific locations on a
substrate and can provide easy and fast deposition of polymer films
over a large area. The demonstration confirms that organic solar cells
can be processed with printing technologies with little or no loss
compared to “clean room” semiconductor technologies such as spin
coating. The most popular printing tool for organic electronics, inkjet
printing could become a smart tool to manufacturer solar cells with
multiple colors and patterns for lower power requirement products, like
indoor or sensor applications. Inkjet printing is considered very
promising because the polymer devices can be fabricated very easily
because of the compatibility with various substrates and it does not
require additional patterning.
About Konarka Technologies, Inc.
Konarka builds products that convert light to energy – anywhere. As the
leading developer of polymer photovoltaic technology that provide a
source of renewable power in a variety of form factors for commercial,
industrial, government and consumer applications, Konarka has a broad
portfolio of patents, technology licenses and an accomplished technical
team. The Company's Power Plastic® technology is focused on delivering
lightweight, flexible, scalable and manufacturable products. Konarka
Technologies is headquartered in Lowell, Mass., U.S.A., with European
headquarters in Nuremberg, Germany, business development offices in
Asia and a research and development facility in Austria. For additional
information, visit http://www.konarka.com.
Source: Konarka Technologies, Inc. Via: http://www.nanowerk.com/news/newsid=4800.php [www.nanowerk.com]
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