While we wait for affordable multi-junction solar cells that are pushing past the 40 percent conversion efficiency mark to make it out of the lab and onto our roofs, we have to make do with standard commercial silicon cells that currently max out at around 19 percent. A team from the University of New South Wales (UNSW) in Australia has found a way to improve the quality of low-grade silicon, enabling higher efficiency solar cells to be produced from cheaper, low-grade silicon.
It’s been known for several decades that hydrogen atoms can be introduced to help correct the efficiency-reducing defects and contaminants found in lower-grade silicon. However, researchers have had limited success in controlling the hydrogen to maximize its benefits. The solution found by the UNSW team relates to controlling the charge state of the hydrogen atoms.
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Hydrogen atoms can exist in a positive, negative or neutral charge state, which determines how well they can move around the silicon and their reactivity, which is important to help correct the defects. The researchers say that by controlling the charge state, it will be possible to achieve higher efficiencies using lower-cost, low-grade silicon.
“We have seen a 10,000 times improvement in the mobility of the hydrogen and we can control the hydrogen so it chemically bonds to things like defects and contaminants, making these inactive,” says Scientia Professor Stuart Wenham from the School of Photovoltaics and Renewable Energy Engineering at UNSW. “This process will allow lower-quality silicon to outperform solar cells made from better-quality materials.”
Wenham expects to achieve efficiencies of between 21 and 23 percent using this new technique, which was patented by the UNSW team earlier this year. The researchers have attracted the interest of industry partners interested in commercializing the technology, and they are working with manufacturing equipment companies to introduce it into solar cell manufacturing processes.