UNSW Team Achieves 12.4% Efficiency for CZTS Solar Cells
Researchers at the University of New South Wales have made a breakthrough in CZTS solar cell technology, achieving a certified efficiency of 12.4% by preventing copper drift during manufacturing.
The University of New South Wales (UNSW) team has identified a manufacturing technique that reduces microscopic defects in copper zinc tin sulphide (CZTS) solar cell material. This breakthrough has achieved record voltage performance for the technology and a certified efficiency of 12.4%. The work, led by Scientia Professor Xiaojing Hao, addresses a defect problem that has limited CZTS efficiency for years.
## Introduction to CZTS Solar Cells CZTS, also known as kesterite, is composed of copper, zinc, tin, and sulphur, elements that are abundant and comparatively non-toxic compared with some competing thin-film semiconductor materials. This makes it an attractive candidate for tandem solar cells, which stack two different materials to capture a broader range of the solar spectrum than silicon alone can absorb.
## Overcoming Manufacturing Challenges The team found that copper in the material tends to drift away from where it is needed during the earliest stages of the high-temperature manufacturing process, leading to unwanted impurities and structural defects at the atomic scale. By strengthening the copper-sulphur bonding during the initial thermal reaction, the team was able to keep the material’s ingredients evenly distributed throughout the manufacturing process, substantially reducing the defects that trap photogenerated electrical charge and lower cell voltage.
The CZTS efficiency roadmap set out by Hao suggests that reaching around 20% efficiency would represent a genuine opportunity for commercial uptake, with intermediate targets of 15% and 17% needed to build confidence in the technology along the way. The biggest hurdle for any new PV technology is ultimately cost, noting that silicon has already been through repeated cost-reduction cycles that rivals must match to compete.
## Comparison of Solar Cell Efficiencies The following table compares the efficiencies of different solar cell technologies: | Technology | Efficiency | | --- | --- | | CZTS | 12.4% | | Silicon | higher than CZTS | | High-bandgap kesterite cells | 13.2% |
The 12.4% result builds on a longer run of UNSW research into kesterite solar cells. The latest work instead targets voltage performance in standard CZTS cells by controlling defects during the manufacturing process itself, rather than through post-treatment. The defect-control principle demonstrated in this research extends beyond CZTS to other multi-element semiconductor materials under development for next-generation solar applications.
The research adds to a broader programme of solar materials work at UNSW. The university has also reported identifying an atomic-scale self-repair mechanism in silicon solar cells under sunlight exposure, and separately warned that the solar industry could exhaust global silver reserves within a short period without wider deployment of commercial-scale module recycling. Despite the improvement, CZTS efficiency remains well below that of commercial silicon cells, and the technology’s path to market depends on further gains before it becomes viable for tandem cell manufacturing.
