Using a novel technology that adds multiple innovations to a
very high-performance crystalline silicon solar cell platform, a
consortium led by the University of Delaware has
achieved a record-breaking combined solar cell efficiency of 42.8
percent from sunlight at standard terrestrial conditions.
That number is a significant advance from the current record
of 40.7 percent announced in December and demonstrates an important
milestone on the path to the 50 percent efficiency goal set by the
Defense Advanced Research Projects Agency (DARPA). In November 2005,
the UD-led consortium received approximately $13 million in funding for
the initial phases of the DARPA Very High Efficiency Solar Cell (VHESC)
program to develop affordable portable solar cell battery chargers.
Combined with the demonstrated efficiency performance of the
very high efficiency solar cells’ spectral splitting optics,
which is more than 93 percent, these recent results put the pieces in
place for a solar cell module with a net efficiency 30 percent greater
than any previous module efficiency and twice the efficiency of
state-of-the-art silicon solar cell modules.
As a result of the consortium’s technical
performance, DARPA is initiating the next phase of the program by
funding the newly formed DuPont-University of Delaware VHESC Consortium
to transition the lab-scale work to an engineering and manufacturing
prototype model. This three-year effort could be worth as much as $100
million, including industry cost-share.
The ground-breaking research was led by Allen Barnett,
principal investigator and UD professor of electrical and computer
engineering, and Christiana Honsberg, co-principal investigator and
associate professor of electrical and computer engineering. The two
direct the University’s High Performance Solar Power Program
and will continue working to achieve 50 percent efficiency, a benchmark
that when reached would mean a doubling of the efficiency of
terrestrial solar cells based around a silicon platform within a
50-month span.
“The University of Delaware is very proud of the
achievements of Allen Barnett and Christiana Honsberg, both their
research and their work in leading the consortium,” UD
President Patrick T. Harker said. “We are grateful to DARPA
for its confidence in the University and very much look forward to
working with DuPont and our other partners in industry, government and
academia on this project, which will have wide application and will be
of particular benefit to our men and women in the service.”
“UD has become an important center for renewable
energy research, and we applaud the efforts of the University-led
consortium,” UD Provost Dan Rich said. “This
project is of vital importance, particularly given the pressing need
for alternative sources of energy.”
"The University is committed to the advancement of
leading-edge research that solves important problems and results in the
invention of new technologies aimed at enhancing society," Carolyn
Thoroughgood, vice provost for research and graduate studies at UD,
said. "This project highlights the quality of research at UD and also
demonstrates the value of collaboration."
“The achievement of this benchmark is a major step
forward in the ongoing development of low-cost solar photovoltaic
technology,” Rhone Resch, president of the Solar Energy
Industries Association, said. “Furthermore, we applaud DARPA
for making a strategic investment in American’s energy
security. We anticipate that this project will result in a wide range
of commercial solar applications that will benefit the U.S. military
and American consumers alike.”
"Many of us have been working with programs to take us to a
real photovoltaic energy future. This project is already working in
that future. DARPA has leapfrogged the 'conventional,' demonstrating
that creativity and focus can significantly accelerate revolutionary
research-bench concepts toward reality, demonstrating this does not
have to take decades,” Lawrence L. Kazmerski, director of the
U.S. Department of Energy’s National Center for Photovoltaics
at the National Renewable Energy Laboratory in Golden, Colo., said.
“This is a first step—but a significant one in
making sure our energy future is what we know it should look like."
The consortium’s goal is to create solar cells that
operate at 50 percent in production, Barnett said. With the fresh
funding and cooperative efforts of the DuPont-UD consortium, he said it
is expected new high efficiency solar cells could be in production by
2010.
The highly efficient VHESC solar cell uses a novel lateral
optical concentrating system that splits solar light into three
different energy bins of high, medium and low, and directs them onto
cells of various light sensitive materials to cover the solar spectrum.
The system delivers variable concentrations to the different solar cell
elements. The concentrator is stationary with a wide acceptance angle
optical system that captures large amounts of light and eliminates the
need for complicated tracking devices.
The VHESC would have immediate application in the
high-technology military, which increasingly relies upon a variety of
electronics for individual soldiers and the equipment that supports
them. As well, it is hoped the solar cells will have a large number of
commercial applications.
Today, the American soldier carries a pack that weighs nearly
100 pounds of which about 20 pounds are the three-day supply of
batteries needed to power their gear. The DARPA program aims to
dramatically reduce the battery logistics pipeline and provide the
soldier with more power at reduced weight, thus improving mobility,
survivability and the availability of advanced electronic technologies
on the battlefield. With the dramatically higher efficiency of the
VHESC technology, solar rechargers could be integrated into common
battlefield devices such as night vision goggles, radios and GPS
navigation systems.
Barnett and Honsberg said that reaching the 42.8 percent mark
is a significant advance in solar cell efficiency, particularly given
the unique small and portable architecture being used by the consortium
and the short time – 21 months – in which it was
developed.
Modern solar cell systems rely on the concentration of the
sun’s rays, a concept similar to youngsters using magnifying
glasses to set scraps of paper on fire. Honsberg said the previous best
of 40.7 percent efficiency was achieved with a high concentration
device that requires sophisticated tracking optics and features a
concentrating lens the size of a table and more than 30 centimeters, or
about 1 foot, thick.
The UD consortium’s devices are potentially far
thinner at less than 1 centimeter. “This is a major step
toward our goal of 50 percent efficiency,” Barnett said.
“The percentage is a record under any circumstance, but
it’s particularly noteworthy because it’s at low
concentration, approximately 20 times magnification. The low profile
and lack of moving parts translates into portability, which means these
devices easily could go on a laptop computer or a rooftop.”