RED BANK, N.J., Sept. 2, 2014 /PRNewswire/ -- In making a
solar cell, scientists etch nanoscale spikes into a silicon wafer
in order to maximize its surface area and consequently to maximize
the amount of sunlight to reach it. Metal particles have been used
as a catalyst in this process because etching is much accelerated
near metal particles.
Initially, gold had been the metal of choice. But at nearly
$3,000 per troy ounce, gold is an
expensive alternative. And so scientists found a way to switch to
silver particles, since silver is much cheaper at around
$20 per troy ounce. Even though a
very small amount of the catalyst is used to make a single solar
cell, the cost saving is significant when building, say, a typical
100MW facility.
But now, scientists working for Natcore Technology Inc.
(TSX-V: NXT; NTCXF.PK) at the Rice
University lab of Prof. Andrew
Barron, a Natcore co-founder, have successfully used copper
as a catalyst. Copper costs about 20¢ per troy ounce, or
1/100th of the cost of silver.
The chemical stew that makes it possible is a mix of copper
nitrate, phosphorous acid, hydrogen fluoride and water. When
applied to a silicon wafer, the phosphorus acid reduces the copper
ions to copper nanoparticles. The nanoparticles aid in removing
electrons from the silicon wafer's surface, thereby oxidizing it.
The oxidized silicon is dissolved by the hydrogen fluoride,
resulting in a process that forges inverted pyramid-shaped
structures into the silicon.
The result of fine-tuning the process is a black silicon layer
with features as small as 590 nanometers (billionths of a meter)
that reflect less than one percent of light. (By comparison, a
clean, un-etched silicon wafer reflects nearly 40 percent of
light.)
"There are still some challenges to overcome," says Prof.
Barron. "The spikes would still require a coating to protect them
from the elements, and we're working on ways to shorten the process
needed to perform the etching in the lab. We also need to
completely remove the copper catalyst in order to extend the life
of the solar cell. But this method is far more practical than
previous methods," he says
"This is another step in our push to bring down the cost of
solar energy and to make it cost-competitive with energy derived
from conventional sources," says Chuck
Provini, Natcore's president and CEO. "By switching from
silver to copper, we'd lower the cost of producing a solar cell by
a fraction of a penny. But over the course of a 100 MW facility,
that's a saving of more than $100,000."
The research by Barron and Rice
graduate student and lead author Yen-Tien
Lu appears in the Royal Society of Chemistry's Journal of
Materials Chemistry A.
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Contact: Chuck Provini
732-576-8800
info@NatcoreSolar.com
SOURCE Natcore Technology Inc.