Novel solar cell architecture to reduce silver costs, improve voltage


From pv magazine Global

U.S. start-up Solar Inventions has announced it has been awarded a patent by the U.S. Patent and Trademark Office for its Configurable Current Cells, or C3, technology, for solar cell manufacturing.

“With U.S. Patent No. 11,145,774 in place, Solar Inventions will be finalising pending C3 patents in China, Europe, India, Japan, Australia, South Korea, Mexico, Israel, [the] United Arab Emirates, Egypt, Brazil, Saudi Arabia, Canada, Turkey, Vietnam, and Taiwan, which together account for 90% of the worldwide solar market,” the company said in a statement.
The manufacturing process is claimed to reduce silver costs by 3% on the front side of the cell, and by 5% on the rear side, while also increasing the overall solar module output by between 2 and 3 W. It consists of connecting sub-cells in series within a single cell in order to increase the device voltage. The sub-cells are created on the wafer without physically cleaving the solar cell, which results in a smaller wafer perimeter compared to the wafer area of the individual solar cells. The sub-cells are electrically divided during the metalisation process.
Each time a solar cell is cut in half, the ratio of the perimeter to the surface increases,” said the company’s CEO, Ben Damiani. “This results in non-ideal diode effects and higher edge recombination velocity for individual half cells.” According to him, the novel technique ensures the same benefits as half-cut cells but without requiring cells to be physically broken and rewired.  Net silver savings are claimed to be proportional to the number of busbars on the cell. “A three-busbar H pattern reduces silver consumption and a six-busbar pattern reduces it further,” he explained.
The proposed cell architecture requires a smaller silver contact area, which reduces the recombination velocity for metal on the silicon surface and results in a 1-5 mV increase of the open-circuit voltage in the solar cell. Furthermore, the lower silver consumption is also said to be responsible for less front metal shadowing, which improves optical transmission into the bulk silicon for absorption and electrical current creation.
“For example, a nine-busbar PERC solar cell would save approximately $1 million in silver per gigawatt of production, while improving performance by 2-3 watts per panel, for an additional $1-2 million worth of power gains,” Damiani emphasized. “The added flexibility of the sub-cell architecture allows for new ways to limit the negative impact of power loss due to higher electrical current, which is directly related to the size of the wafer inside a solar module.”
The manufacturer also claims the C3 technology can be applied in existing solar module factories, as it requires no changes to the tabbing and stringing of the products.
In a recent interview with pv magazine, US analyst Matthew Watson said that the share of silver in PV module costs had risen by around 5% in recent months to account for approximately 10% of the total. “With PV module costs in the neighbourhood of $0.018-$0.019/watt and silver representing around 10% of the overall module cost structure, and module and cell prices still declining, finding a means to lower the silver cost component is going to become an increasingly difficult task,” Watson stated. “Over the past 20 years, silver has averaged an 8.31% year-on-year growth in prices, which is greater than the current rate of design thrifting. This means lowering that silver $/watt component is going to be very difficult.”

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