Zero energy buildings a step closer following UNSW solar breakthrough

Buildings with roofs, facades and windows swathed in solar are a step closer following news that the University of NSW has broken efficiency records for CZTS thin-film solar.

While traditional thin-film solar is made from scarce, expensive and toxic materials, CZTS thin-film technology uses the benign and abundant materials copper, zinc, tin and sulphur – meaning price spikes are less likely as demand increases, and safety is less of a concern.

The efficiency record confirmed by the US’s National Renewable Energy Laboratory is only 7.6 per cent, though the researchers expect it won’t be long until the technology hits 20 per cent – most likely in the next few years.

According to UNSW’s Professor Martin Green, the CZTS technology has additional benefits over competing solar cells.

“They can be deposited directly onto materials as thin layers that are 50 times thinner than a human hair, so there’s no need to manufacture silicon ‘wafer’ cells and interconnect them separately,” he said. “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.”

Though the current efficiency is small, the cheapness of the material and the ease at which it can move from lab to commercialisation means we could soon see applications in the real world. Indeed, UNSW is already working with a number of companies keen to use the technology even before it gets its efficiency up to 20 per cent.

“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,” Dr Hao said.

The lack of toxicity is an element she says might pique the interest of a construction industry mindful of the legacy of materials like asbestos, and boost the profile of building-integrated photovoltaics, already valued at $1.6 billion globally.

Dr Xiaojing Hao, who led the research, expects that being able to deposit durable, flexible and cheap CZTS cells on various surfaces will lead to them being widely integrated into buildings facades, roof tiles and glazing – meaning zero-energy or energy-positive buildings will be easier to achieve.

This story was republished with permission from The Fifth Estate.

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