UNSW takes out CZTS efficiency world record

A team from UNSW’s Australian Center for Advanced Photovoltaics has achieved a 7.6% efficiency record for a "full sized" CZTS PV cell. The result has been confirmed by the National Renewable Energy Laboratory (NREL).

The UNSW team is lead by Xiaojing Hao, who claims that her team is "on the way" to rivaling leading thin film technologies cadmium telluride (CdTe) and copper indium gallium selenide (CIGS).

"This is the first step on CZTS’s road to beyond 20% efficiency, and marks a milestone in its journey from the lab to [a] commercial product," said Hao. "There is still a lot of work needed to catch up with CdTe and CIGS, in both efficiency and cell size." Hao added that she sees the 20% efficiency being reached "probably… within the next few years."

The UNSW team note that CZTS cells use abundant materials, and do not contain any toxic cadmium or selenium. As such, CZTS semiconductors are cheap to produce and can be manufactured using techniques that are already commercially available. The UNSW team is currently employing a sputtering followed by sulfurization process to produce its CZTS cells.

Renowned PV researcher Martin Green, Xiaojing Hao’s mentor at the UNSW, said that CZTS material is additionally of interest in tandem applications with crystalline silicon (c-Si).

"We’re interested in these higher bandgap CZTS cells for two reasons," said Green. "They… 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." Green, considered a pioneer in the crystalline silicon field, is currently developing c-Si-perovskite tandem cells.

Hao noted that CZTS’ benign environmental profile and its ability to be deployed flexible applications made it ideal for BIPV applications. She added that many efficiency-boosting "tricks" that have been employed by CIGS and CdTe developers and manufacturers could be applied to CZTS technology, potentially accelerating its efficiency roadmap.

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