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21 Oct 2014
Laser processing step means that cells can be produced without need for expensive high-temperature furnace.
Natcore Technology, a Toronto-listed company developing new methods to make solar cells and other optical components, says its engineers have demonstrated a way to further cut the cost of generating electricity through photovoltaics.
The firm’s laser processing step suggests that a key part of solar cell production - annealing at temperatures in excess of 850 °C to create an anti-reflective layer - would no longer be needed, and that the devices could be manufactured without using temperatures higher than 350 °C at any point.
“This development sets the stage for a marriage between Natcore's highly specialized laser processing and its black silicon technology,” it claims in a press release. “The fruits of that all-low-temperature marriage would include gains in efficiency and significantly lower production costs.”
Natcore describes the demonstration, which took place on a single cell at its research laboratories in Rochester, New York, as “uniquely suited” to large-scale manufacturing, especially with regard to high-performance, back-contacted cells.
“Exposure to 850°C and above, the temperature typically used for conventional solar cells, requires specialized equipment,” it explains. That kind of temperature demands the use of a special furnace with a quartz or similar interior, something that Natcore says is completely unnecessary with its new process.
Black silicon
“We’re changing how solar cells are made,” claims the firm on its web site, citing its exclusive technology licenses with the likes of Rice University and the US National Renewable Energy Laboratory (NREL).
The technology relies on a combination of laser processing and so-called “black silicon”, which refers to the anti-reflective appearance of a silicon wafer that has been etched to create thousands of tiny “pores” on its surface. The material actually looks dark blue in color.
US firm SiOnyx is also working on applications of the novel material, although for security uses like night vision rather than solar technology.
“Applying a black silicon etch is a very inexpensive anti-reflective process,” said Chuck Provini, Natcore's CEO. “Laser processing is also relatively low-cost, because it reduces energy and chemical costs associated with the furnace that it replaces.
“We believe that our proprietary technology will be in great demand, and we will move to license it to the right partner as soon as possible.”
Natcore is anticipating additional benefits, aside from removing the need for a high-temperature furnace. It says that by eliminating such steps it will be possible to maintain the cell junction’s minority carrier lifetime, which should help to improve conversion efficiencies.
The company claims that in recent tests its scientists have achieved an open-circuit voltage above 0.6 V, suggesting that the devices are close to matching the efficiency of today's high-end commercial cells but with lower manufacturing cost.
The next steps in its development roadmap will be to add black silicon anti-reflection control to the front side of cells and eliminate the front contacts, something that should increase cell output by 3-4 per cent.
Having announced a collaboration with the Fraunhofer Institute for Solar Energy Systems (ISE) earlier this year, Natcore is also involved in a joint-venture plan to manufacture solar cells in Australia – mooting ambitious ideas including a 100 MW per year production facility.
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