Soaking up the summer sun could mean a good source of power that lowers your
fuel bills. But today’s solar cells aren’t cheap or efficient
enough for widespread use. As this ScienCentral News video reports, some researchers
in nanotechnology are hard at work trying to change that.
Nanoscale Cells, Mega Energy
According to the National
Renewable Energy Laboratory, the U.S. Department of Energy’s center
of solar-power research, about every 40 minutes enough of the sun’s
energy reaches the earth to meet everyone’s needs for electric power
for an entire year. The worldwide solar power industry is growing rapidly,
but it’s still relatively small compared to oil, gas and coal. If the
industry is to keep expanding, solar cells must become less expensive and
more efficient.
But Alivisatos also is interested in another use for quantum dots, as part
of solar cells. When he read a report from the National
Academy of Sciences on alternatives
to fossil fuels, he was struck by its conclusions. Today’s solar
cells aren’t efficient enough for widespread use. They also are made
of silicon wafers, and like silicon chips, they must be manufactured under
expensive high-tech conditions. “The existing solar-cell technologies
were off by a very substantial factor from what was really needed,”
Alivisatos says. Solar energy needed “someone to come up with a new
type of design.”
Solar cells that include nanorods.
A rod is a key component of a solar cell, the part
that draws and absorbs the sun’s energy. Alivisatos decided that quantum
dots’ strong semi-conducting properties—and the fact that they
are grown in water—meant that they could be used to make nanoscale rods.
To keep the rods properly aligned inside a solar cell so that they absorb
solar energy consistently, he and his research team make them in the shape
of branching
nanocrystals that they call tetrapods.
“Imagine a pyramid with all four sides exposed,” Alivisatos says.
“We can grow rods out of each face of that pyramid. The result looks
like a jack, from the children’s game. It’s a semiconductor that
will always stand up on a surface, and should perform more efficiently.”
Solar cells that include nanorods.
A rod is a key component of a solar cell, the part
that draws and absorbs the sun’s energy. Alivisatos decided that quantum
dots’ strong semi-conducting properties—and the fact that they
are grown in water—meant that they could be used to make nanoscale rods.
To keep the rods properly aligned inside a solar cell so that they absorb
solar energy consistently, he and his research team make them in the shape
of branching
nanocrystals that they call tetrapods.
“Imagine a pyramid with all four sides exposed,” Alivisatos says.
“We can grow rods out of each face of that pyramid. The result looks
like a jack, from the children’s game. It’s a semiconductor that
will always stand up on a surface, and should perform more efficiently.”
Next, Alivisatos tackled the question of a cheaper, simpler means of manufacturing
solar cells. He came up with a method that “looks much more like the
casting of a thin, flexible plastic film than the conventional fabrication
of solar cells.” He combines his tetrapods in their solution with plastic,
to make solar cells in the form of extremely thin sheets. These sheets can
be rolled out like newsprint, “a low-cost, high-volume technique.”
They might be ink-jet printed, or even painted onto surfaces like car roofs.
Alivisatos is cofounder of Nanosys,
a nanotechnology start up company. Nanosys has secured major funding from
Matsushita
Electric to market solar roofing tiles using Alivisatos’ design
by 2007. This research appeared in the June, 2003 issue of Nature Materials.
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