27 July 2012
Breakthrough technology promises photovoltaics from any semiconductor
A new technology
that could enable low cost, high efficiency solar cells to be made from
virtually any semiconductor material has been developed by researchers
at the US Department of Energy's Lawrence Berkeley National Laboratory
and the University of California Berkeley.
The technology,
they believe, opens the door to the use of plentiful, relatively
inexpensive semiconductors such as metal oxides, sulfides and
phosphides, which have previously been considered unsuitable for solar
cells because of the difficulty in chemically tailoring their
properties.
"Solar technologies today face a cost to efficiency trade off that has
slowed widespread implementation," said physicist Alex Zettl, who led
the research. "Our technology reduces the cost and complexity of
fabricating solar cells and thereby provides what could be an important
cost effective and environmentally friendly alternative that would
accelerate the usage of solar energy."
The researchers have dubbed the technology 'screening-engineered
field-effect photovoltaics', or SFPV, because it utilises the electric
field effect, a phenomenon by which the concentration of charge carriers
in a semiconductor is altered by the application of an electric field.
With the SFPV technology, a carefully designed partially screening top
electrode lets the gate electric field penetrate the electrode and more
uniformly modulate the semiconductor carrier concentration and type to
induce a p-n junction. This enables the creation of high quality p-n
junctions in semiconductors that are extremely difficult to dope by
conventional chemical methods.
"Our technology requires only electrode and gate deposition, without the
need for high temperature chemical doping, ion implantation, or other
expensive or damaging processes," noted Zettl. "The key to our success
is the minimal screening of the gate field which is achieved through
geometric structuring of the top electrode. This makes it possible for
electrical contact to and carrier modulation of the semiconductor to be
performed simultaneously."
Under the SFPV system, the architecture of the top electrode is
structured so that at least one of the electrode's dimensions is
confined. "Our demonstrations show that a stable, electrically contacted
p-n junction can be achieved with nearly any semiconductor and any
electrode material through the application of a gate field, provided
that the electrode is appropriately geometrically structured," Zettle
concluded.
Author
Laura Hopperton
Supporting Information
Websites
http://www.lbl.gov/
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