UNSW reaches record rating for CZTS solar cells
A University of New South Wales NSW team has achieved the world's highest efficiency rating for a full-sized thin-film solar cell using CZTS (copper, zinc, tin and sulphur).
NREL, the USA's National Renewable Energy Laboratory, confirmed the 7.6 percent efficiency in a 1cm2 area CZTS cell this month.
Unlike its thin-film competitors, CZTS cells are made from abundant materials and have none of the toxicity problems of its two thin-film rivals, CdTe and CIGS.
"This is the first step on CZTS's road to beyond 20 percent efficiency, and marks a milestone in its journey from the lab to commercial product," said Xiaojing Hao who led the research. "There is still a lot of work needed to catch up with CdTe and CIGS, in both efficiency and cell size, but we are well on the way."
In addition to its elements being more commonplace and environmentally benign, the team is interested in these higher bandgap CZTS cells because they can be deposited directly onto materials as ultra thin layers so there's no need to manufacture silicon 'wafer' cells and interconnect them separately. "They also respond better than silicon to blue wavelengths of light, and can be stacked as a thin-film on top of silicon cells to ultimately improve the overall performance," added Martin Green, a mentor of Hao.
By being able to deposit CZTS solar cells on various surfaces, Hao's team believes this puts them firmly on the road to making thin-film photovoltaic cells that can be rigid or flexible, and durable and cheap enough to be widely integrated into buildings to generate electricity from the sunlight that strikes structures such as glazing, façades, roof tiles and windows.
UNSW is collaborating with a number of large companies keen to develop applications well before it reaches 20 percent efficiency - probably, Hao says, within the next few years.
"I'm quietly confident we can overcome the technical challenges to further boosting the efficiency of CZTS cells, because there are a lot of tricks we've learned over the past 30 years in boosting CdTe and CIGS and even silicon cells, but which haven't been applied to CZTS," said Hao.
