Natcore Scientists Create "Absolute Black"
March 29 2012 - 9:22AM
Marketwired
Scientists at Natcore Technology Inc. (TSX VENTURE:NXT)(PINK
SHEETS:NTCXF), using simple liquid bath processes, have created a
black surface on a silicon wafer with an average reflectance in the
visible and near-infrared region of the solar spectrum of 0.3%,
making it the "blackest" silicon solar cell surface ever recorded.
Compared with standard production cells now available, this
represents a tenfold reduction in reflectance over that portion of
the spectrum, which is the source of about 80% of the usable power
that can be drawn from sunlight.
The black color of black silicon results from the near-total
absence of reflected light from the porous wafer surface. With
solar cells, "blackness" is highly desirable because it indicates
that incident light is being absorbed for conversion to energy
rather than being reflected and thus wasted.
Quantitatively, reflectance is the proportion of light striking
a surface that is reflected from it. Thus a reflectance of 0.3%
means that only 0.3% of incident light is reflected from the solar
cell's surface, while 99.7% of incident light is absorbed by the
cell and is available for conversion into electrical energy.
A tenfold reduction in reflectance would mean that up to 3% more
usable light would get into the cell, effectively increasing the
cell efficiency by that amount. (An 18% efficient cell becomes an
18.5% cell, for example.)
But there are additional benefits to be derived from black
silicon. A panel made from black silicon solar cells will produce
significantly more energy on a daily basis than will a panel made
from cells using the industry standard antireflective coating.
First, because it reflects less light. Second, because it performs
better during the morning and afternoon hours when the sun hits at
an angle. (It also outperforms standard cell panels on cloudy
days.) Its higher energy output, combined with a lower cost using
Natcore's patented process, could quickly make black silicon the
global solar technology of choice.
Natcore's process began with an uncoated, textured silicon wafer
that had an average reflectance of approximately 8%, giving it a
mottled gray appearance. First, nanoscale pores were etched into
the wafer surface by submerging it for a few minutes in a liquid
solution at room temperature. Next, using the company's liquid
phase deposition (LPD) process, Natcore scientists filled the pores
and then over-coated them with silicon dioxide. This combination
step both coated and passivated, thereby allowing lower
reflectance. After the surface treatments were completed, the
wafers were taken to the State of Ohio's Photovoltaic Research and
Development Center at the University of Toledo, where the
reflectance was measured.
This is the latest milestone in Natcore's drive to improve the
performance of solar cells. Conventional cells, with antireflective
coatings made via a chemical vapor deposition process that requires
a high-temperature vacuum furnace and hazardous gases, have a
reflectance of about 4%. With black silicon, the U.S. Department of
Energy's National Renewable Energy Laboratory (NREL) lowered the
number below 2%. Now Natcore's technology has reduced it to 0.3%,
or virtually zero. "Absolute black is to reflected light as
absolute zero is to heat," says Dr. Dennis Flood, Natcore's Chief
Technology Officer. "And getting close to zero reflectance with a
process that we can use for the production of commercial solar
cells is simply astounding."
Natcore was recently granted an exclusive license by NREL to
develop and commercialize a line of black silicon products based on
NREL patents. Natcore's reflectance accomplishment came about as a
natural part of its work associated with that license.
"We are already working with two equipment manufacturers to
design a production tool," says Natcore President and CEO Chuck
Provini. "The tool would make 2,000 black silicon wafers per hour.
We'll establish other parameters in our lab. When the design is
completed, we'll take orders for the tool. We have already begun
talking with potential customers in Italy, China and India."
"This latest achievement further strengthens our position as the
sole provider of the best antireflection control technology
available to silicon solar cell manufacturers," adds Provini.
William Farris, NREL's Vice President of Commercialization &
Technology Transfer, says "NREL has a long history of working with
companies to move renewable energy technologies to the market.
We're encouraged and gratified at Natcore's success as it relates
to our commercial license agreement for NREL's black silicon
technology."
Statements in this press release other than purely historical
factual information, including statements relating to revenues or
profits, or Natcore's future plans and objectives, or expected
sales, cash flows, and capital expenditures constitute
forward-looking statements. Forward-looking statements are based on
numerous assumptions and are subject to all of the risks and
uncertainties inherent in Natcore's business, including risks
inherent in the technology history. There can be no assurance that
such forward-looking statements will prove to be accurate, as
actual results and future events could differ materially from those
anticipated in such statements. Accordingly, readers should not
place undue reliance on such statements. Except in accordance with
applicable securities laws, Natcore expressly disclaims any
obligation to update any forward-looking statements or
forward-looking statements that are incorporated by reference
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Contacts: Natcore Technology Inc. Chuck Provini 732-576-8800
www.natcoresolar.com