Engineers at the University of New South Wales (UNSW) have shattered the global efficiency record for a promising new solar cell material, achieving a 10.7% certified power conversion rate for antimony chalcogenide cells. This breakthrough, led by Scientia Professor Xiaojing Hao from UNSW’s School of Photovoltaic and Renewable Energy Engineering, has earned the material its first-ever entry in the prestigious international Solar Cell Efficiency Tables and could pave the way for cheaper, more durable, and highly efficient tandem solar panels.
For years, the efficiency of antimony chalcogenide—a material seen as a prime candidate for the next generation of solar technology—had frustratingly stalled below 10%. The UNSW team’s discovery, published in the journal Nature Energy, didn’t just break through that barrier; it solved the fundamental chemical puzzle holding the material back. They identified that uneven distribution of sulfur and selenium during manufacturing created an “energy barrier,” trapping electrical charges and crippling performance. “It was like driving a car up a steep slope,” explained the paper’s first author, Dr. Chen Qian. “If you do that, you need to use more fuel… When the distribution of the elements inside the cell is more even, then the charge can move more easily.”
The elegant solution, according to their research, was the addition of a small amount of sodium sulfide during the hydrothermal deposition process. This simple tweak stabilized the chemical reactions, smoothed out the elemental distribution, and allowed the team to achieve a lab efficiency of 11.02%, later independently certified at 10.7% by CSIRO. This verification marks the highest independently verified performance for this material anywhere in the world, reported the university’s announcement.
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Why does this niche efficiency record matter for the future of solar power? The answer lies in tandem cells, the inevitable next step for photovoltaic technology. “The next generation of technology for solar panels is tandem cells, which is where two or more solar cells are stacked on top of each other,” stated Professor Hao. Each layer absorbs a different part of the sunlight spectrum, boosting overall efficiency far beyond what silicon alone can achieve. The hunt is on globally for the ideal material to serve as the efficient, stable, and affordable top layer in these stacks, and antimony chalcogenide (Sb2(S,Se)3) now has a compelling résumé.
The advantages are significant, according to the UNSW team. The material is made from abundant, low-cost elements, avoiding the reliance on rare or expensive metals that plague some alternatives. It’s inorganic, meaning it’s inherently more stable and durable than some organic competitors. Perhaps most strikingly, it’s incredibly thin-film efficient; a layer just 300 nanometres thick—one-thousandth the width of a human hair—can harvest sunlight powerfully. This opens doors far beyond rooftop panels. Its semi-transparent nature and high “bifaciality” make it perfect for futuristic solar windows, a path being explored by UNSW spinout company Sydney Solar for solar “stickers.”
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Furthermore, the material’s properties are a strong match for the emerging world of indoor photovoltaics. Its bandgap aligns well with the spectrum of indoor lighting, making it a safe and stable candidate to power smart badges, sensors, and other devices in the Internet of Things, where constant efficiency under low light trumps raw peak power. The team, which also includes Dr. Jialiang Huang, acknowledges that work remains. They are now focused on a process called passivation to further reduce material defects, confident they can push efficiencies toward 12% in the near future.
This record is more than a number in a table. It’s a validation of a material’s potential and a masterclass in problem-solving. By moving from a fundamental chemistry breakthrough to a certified world record, the UNSW researchers have not only accelerated the timeline for antimony chalcogenide but have also strengthened the global portfolio of options for building the ultra-efficient, ubiquitous solar technology of tomorrow.
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