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The cost of solar electricity has
been reduced 100-fold over the past
two decades, but further reductions
are needed before solar power is widely
used. Scientists at the National Renewable
Energy Laboratory took major steps
toward this goal by designing photovoltaic
cells (which convert sunlight to electricity)
with 30 percent efficiency, much higher
than the 10-20 percent levels achieved
previously. The new cells consist
of thin layers of semiconductors applied
to a low-cost backing, such as glass
or plastic. The researchers received
Office of Science support to develop
a basic understanding of the opto-electronic
properties of various semiconductors.
Calculations of electronic structure
provided the knowledge needed to precisely
engineer layered semiconductors. Then,
a tandem device was designed with
two solar cells made of materials
that respond to different parts of
the solar spectrum; the top cell (made
of gallium indium phosphide) absorbs
the high-energy component of sunlight
and passes the rest to the bottom
cell (made of gallium arsenide) for
absorption. Researchers are working
on the addition of a third cell to
push efficiency to more than 40 percent,
to open up new opportunities for terrestrial
and space applications.
Scientific Impact:
These advances have added to the scientific
and engineering knowledge base needed
to make solar power more practical
and useful. For instance, the material
used in the top layer of the new device
is much more resistant to radiation
damage than conventional silicon and
thus will have a longer useful life.
Social Impact: The
technology was transferred to a major
supplier of photovoltaic cells for
space power, and four satellites using
it are in orbit, flashing back telephone
and television signals. The new solar
cells provide as much as 50 percent
more power than previous cells, so
the satellites can carry more communications
links, experiments, or other projects
and operate more economically.
Reference: Cotal,
H. L.; Lillington, D. R.; Ermer, J.
H.; King, R. R.; Karam, N. H.; Kurtz,
S. R.; Friedman, D. J.; Olson, J.
M.; Ward, S.; Duda, A.; Emery, K.
A.; Moriarty, T. (2000). "Highly Efficient
32.3% Monolithic GaInP/GaAs/Ge Triple
Junction Concentrator Solar Cells."
Program and Proceedings: NCPV
Program Review Meeting 2000,
16-19 April 2000, Denver Colorado.
BK-520-28064. Golden, CO: National
Renewable Energy Laboratory; pp. 111-112;
NICH Report No. CP-520-29664.
URL:
http://www.nrel.gov/ncpv/pvmenu.cgi?site=ncpv&idx=1&body=world.html
Technical Contact:
Press Contact: Jeff
Sherwood, DOE Office of Public Affairs,
202-586-5806
SC-Funding Office:
Office of Basic Energy Sciences |
