Natcore has successfully eliminated silver from an all-back-contact silicon heterojunction cell, and replaced it with aluminum. No loss of performance was said to have been recorded at the companys R&D center in Rochester, the U.S. A provisional patent application is expected to be filed in the next two weeks.
Although it boasts high conductivity, silver is very expensive. And, while twice as much aluminum is needed as silver, "raw material costs would still be just 0.6% of the direct material cost of using silver in the cell," says Natcore.
Currently, silver costs around US$15.28 per troy ounce contributing to roughly 30% of a silicon cells production cost whereas the same quantity of aluminum is said to cost $0.05. The average solar panel is calculated to use around one-half of an ounce of silver, comprising around 11% of a solar modules raw material cost, adds the company.
On July 9, Natcore announced it had developed a "breakthrough" cell structure "that will simplify the production process, significantly lower costs, and speed the path toward ultra high-efficiency cells." This claim was based on eliminating silver from mass produced solar cells.
"Natcore’s new cell is an all-back-contact heterojunction structure using thin amorphous silicon layers in combination with a standard crystalline silicon solar wafer. The cell could utilize a novel packaging approach in which a flex circuit is directly bonded to multiple, small contact pads by high-speed laser fusion," explained the company at the time.
As part of its path to removing silver from production processes, Natcore said last September it had switched from using silver to copper as a catalyst in silicon wafers instead of silver, with copper costing, at the time, just $0.20 per troy ounce. However, it was noted that the copper would have to also be removed, to extend the life of the solar cell.
"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," commented Chuck Provini, Natcore’s president and CEO on the back of the news in September.
pv magazine has contacted Natcore for more details on its latest announcement.