Researchers Claim Photovoltaic Cell advance

By Amir Ben-Artzi
EE Times Europe
April 30, 2008

Netanya, Israel Scientists at the University of Tel Aviv in Israel
claim they have found a way to construct efficient photovoltaic
cells costing at least a hundred times less than conventional
silicon based devices, and with similar or better energy conversion efficiency.

The reactive element in the researchers' patent pending device is
genetically engineered proteins using photosynthesis for production
of electrical energy.

The scientists applied genetic engineering and nanotechnology for
the construction of a hybrid nano -- bio, solid state device.
According to the researchers, although using photosynthesis for
photovoltaic application is not new, their specific technique is the
first to enable the production of useful photosynthesis-based
photovoltaic cells.

The Israeli team is set to challenge others who are using
photosynthesis for photovoltaic cells, including universities such
as Cambridge in the U.K., and Stanford, M.I.T, the U.S. Naval
Research Laboratory, and the Universities of Tennessee and Arizona
in the U.S, and several others.

The researchers suggest existing silicon based photovoltaic cells
offer low average energy conversion efficiency of 12-14 percent,
while their system is capable of efficiencies of about 25 percent.
They based their photovoltaic device on genetically engineered dry
proteins photosystem I (PS I), encapsulated in solid state substrate
bottom metal and a top transparent electrode.

They also claim that PS I generates a stable charge separation in
200 ns across 6 nm of protein to generate an electric potential of 1
V with quantum efficiency of 1 and absorbed energy conversion
efficiency of 47 percent. A further advantage of PS I is said to be
its transparency to infrared radiation, which eliminates the need
for expensive cooling equipment.

The researchers include Prof. Chanoch Carmeli, Dr. Shachar Richter,
Dr. Itai Carmeli and Prof. Yossi Rosenwaks. Ramot, Tel Aviv
University's technology transfer company, is set to help
commercialize the invention.

Larry Loev, director of business development for high technologies
at Ramot told EETimes the low cost of the proposed device is based
on the low cost of PS I in comparison to silicon. While one square
meter of PS I should cost around $1, a similar area made of silicon
should cost around $200.

"We connected our device to electrodes and we saw how it converts
light to electricity," said Loev.

EETimes Europe has learned that Ramot will probably use the
industrial facilities of solar energy specialist Millennium Electric
T.O.U Ltd. (Raanana, Israel) for making prototype devices,
including engineering of the prototype up scaling, automation of
production and the integration of the university's photovoltaic cell
with other components in the final device. Ramot aims to develop a
cost effective device of 10mm X 10mm in size within three years.

Asked about the competition, Loev claimed: "Certainly many
researchers are looking into how to use photosynthesis to create
photovoltaic cells. However, a deeper look at what has been
published shows major differences between what our group has
achieved and the rest. First, ours is the only group to utilize an
organic material in a dry and stable environment.

"Other groups have only done this under aqueous conditions which are
much less robust. Second, we are able to directly metallize the
protein and make good electronic coupling to the electrodes. Other
groups have utilized intermediate polymers for this purpose, which
is a very complicated procedure. Third, we have demonstrated
multilayer capability, which is crucial to getting good efficiency."


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