Catania,
Italy, September 30, 2003 - STMicroelectronics (NYSE: STM), one
of the world's leading manufacturers of semiconductor devices, today
released details of an advanced research program that it hopes will
substantially reduce the cost of generating electricity from solar
power. The research team, based in Catania and Naples, Italy, is focusing
on applying ST's expertise in nanotechnology to the development of
new solar cell technologies that will eventually be able to compete
commercially with conventional electricity generation methods such
as burning fossil fuels or nuclear reactors.
Photovoltaic systems (solar cells) convert energy from sunlight into
electrical power and are potentially one of the most important renewable
energy sources. However, existing solar cell technologies are mainly
based on semiconductor materials such as silicon and therefore involve
high material* costs. Consequently, although the "fuel" for a solar-powered
generator is free sunlight, the overall cost of solar-generated electricity
(amortized over the lifetime of the solar cell, typically 20 years)
is around ten times higher than the cost of electricity generated
by burning fossil fuels.
Semiconductor-based solar cells have the highest efficiency (defined
as the electrical energy produced for a given input of solar energy)
but there is little that can be done to either increase the efficiency
or reduce the manufacturing cost. ST is therefore pursuing alternative
approaches in which the aim is to produce solar cells that may have
lower efficiencies (e.g. 10% instead of 15-20%) but are much cheaper
to manufacture.
"Although there is much support around the world for the principle
of generating electricity from solar power, existing solar cell technologies
are too expensive to be used on an industrial scale. The ability to
produce low cost, high efficiency solar cells would dramatically change
the picture and revolutionize the field of solar energy generation,
allowing it to compete more effectively with fossil fuel sources,"
says Dr. Salvo Coffa, who heads the ST research group that is developing
the new solar cell technology.
The ST team is following two approaches. One of these, invented in
1990 by Professor Michael Graetzel of the Swiss Federal Institute
of Technology, uses a similar principle to photosynthesis. In a conventional
solar cell, a single material such as silicon performs all three of
the essential functions, which are absorbing sunlight (converting
photons into electrons and holes), withstanding the electric field
needed to separate electrons and holes, and conducting the free carriers
(electrons and holes) to the collecting contacts of the cell. To perform
these three tasks simultaneously with high efficiency, the semiconductor
material must be of very high purity, which is the main reason why
silicon-based solar cells are too costly to compete with conventional
means of producing electric power.
In contrast, the Graetzel cell, known as the Dye-Sensitized Solar
Cell (DSSC), mimics the mechanism that plants use to convert sunlight
into energy, where each function is performed by different substances.
The DSSC cell uses an organic dye (photosensitizer) to absorb the
light and create electron-hole pairs, a nanoporous (high surface area)
metal oxide layer to transport the electrons, and a hole-transporting
material, which is typically a liquid electrolyte.
"One of the most exciting avenues we are exploring is the replacement
of the liquid electrolytes that are mostly used today for the hole-transport
function by conductive polymers. This could lead to further reductions
in cost per Watt, which is the key to making solar energy commercially
viable," says Coffa.
The ST team is also developing low cost solar cells using a full organic
approach, in which a mixture of electron-acceptor and electron-donor
organic materials is sandwiched between two electrodes. The nanostructure
of this blend is crucial for the cell performance because the electron-donor
and electron-acceptor materials have to be in an intimate contact
at distances below 10 nm. ST plans to use Fullerene (C60) as the electron-acceptor
material and an organic copper compound as the electron-donor.
"These R&D activities, which exploit the expertise we have in nanotechnology,
complement and augment the commitment that ST has made to be a CO2-neutral
company by 2010," says Coffa. "In addition to ensuring that our own
industrial activities have minimal impact on the environment, we are
developing many new technologies that we hope will bring substantial
ecological benefits."
About STMicroelectronics
STMicroelectronics is a global leader in developing and delivering
semiconductor solutions across the spectrum of microelectronics applications.
An unrivalled combination of silicon and system expertise, manufacturing
strength, Intellectual Property (IP) portfolio and strategic partners
positions the Company at the forefront of System-on-Chip (SoC) technology
and its products play a key role in enabling today's convergence markets.
The Company's shares are traded on the New York Stock Exchange, on
Euronext Paris and on the Milan Stock Exchange. In 2002, the Company's
net revenues were $6.32 billion and net earnings were $429.4 million.
Further information on ST can be found at http://www.st.com.
* Notes for Editors
Silicon is the material of choice for integrated circuits ("silicon
chips") because a large number of complex circuits, each containing
millions of transistors, can be built on a single wafer of pure silicon
crystal, typically measuring 300mm in diameter. In this case, the
high value of the function performed by each silicon chip (e.g. a
GPS receiver or a DVD decoder) greatly outweighs the cost of the starting
material. For solar cells, where a simple function must be performed
over a large surface area, the converse is true and the cost of the
pure silicon crystal dominates. This is why ST's research program
is particularly focused on applying its expertise in nanotechnology,
derived from its pre-eminence in silicon engineering, to lower cost
materials.
