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Adding sodium sulfide fixed uneven sulfur and selenium distribution, removing energy barriers and unlocking higher efficiency in stalled solar cells.
Researchers in Australia have achieved a breakthrough in an emerging solar cell material that could shape the future of photovoltaic technology.
The team at the University of New South Wales (UNSW) has set a new performance benchmark for antimony chalcogenide solar cells, reaching a certified efficiency of 10.7 percent — the highest independently verified result globally.
Beyond the record result, the researchers also identified the key chemical mechanism underlying the fabrication process, providing critical insights that could accelerate further improvements in efficiency, cost, and durability.
In December 2025, researchers in South Korea claimed to have developed transparent solar windows that generate electricity during the day from sunlight and at night from indoor lighting.
Researchers at UNSW consider tandem solar cells to be the next major advance in photovoltaic technology, with the potential to significantly enhance the efficiency of future solar panels.
Tandem designs stack two or more solar cells, allowing each layer to absorb different parts of the solar spectrum and generate more electricity than conventional single-junction cells. A key challenge for scientists worldwide is identifying suitable materials for the top cell that can effectively pair with today’s dominant silicon technology.
Antimony chalcogenide is emerging as a promising candidate for this role. The material is composed of abundant, low-cost elements, avoiding reliance on scarce or expensive resources used in some high-performance solar technologies. Its inorganic nature also provides greater stability, reducing the risk of long-term degradation.
In addition, antimony chalcogenide has a high light absorption coefficient, meaning skinny layers can efficiently capture sunlight. The material can also be deposited at relatively low temperatures, lowering manufacturing energy demands and supporting scalable, cost-effective production.
Despite its promising properties, progress in antimony chalcogenide solar cells had stalled for several years, with efficiencies failing to rise beyond 10 percent since 2020. Researchers now say the main obstacle was the way the material was formed during manufacturing. The two key elements, sulfur and selenium, were not evenly distributed as the solar-absorbing layer was deposited, which limited performance.
This uneven composition created an internal energy barrier within the solar cell, hindering the flow of the electrical charge generated by sunlight. As a result, much of the charge was lost before it could be collected and converted into usable electricity. By identifying this underlying issue, the researchers were able to target the root cause of the long-standing efficiency plateau.
The breakthrough came with the introduction of a small amount of sodium sulfide during fabrication. This addition stabilised the chemical reactions involved in forming the absorber layer, leading to a more uniform distribution of sulfur and selenium. With the internal barrier reduced, electrical charges could move more freely through the material, significantly improving performance.
Using this approach, the improved solar cells achieved an efficiency of 11.02 percent in laboratory testing, with an independently certified result of 10.7 percent. While further work is needed to reduce defects within the material, researchers say these can likely be addressed through established chemical passivation techniques.
Beyond tandem solar panels, antimony chalcogenide opens the door to a range of new applications. Its ultrathin and semi-transparent nature makes it suitable for see-through solar windows and window-mounted solar films. The material also performs well under indoor lighting, making it attractive for low-power electronics such as smart badges, sensors, e-paper displays, and connected devices, where stability and low-light performance are critical.
“In the next few years, we will continue to work on reducing the defects in this material via that passivation process. We believe an achievable aim is to increase the efficiency up to 12% in the near future by addressing the challenges that still remain, one step at a time,” said Dr Chen Qian, a post-doctoral fellow at the Photovoltaic and Renewable Energy Engineering at UNSW, said in a statement.
Jijo is an automotive and business journalist based in India. Armed with a BA in History (Honors) from St. Stephen's College, Delhi University, and a PG diploma in Journalism from the Indian Institute of Mass Communication, Delhi, he has worked for news agencies, national newspapers, and automotive magazines. In his spare time, he likes to go off-roading, engage in political discourse, travel, and teach languages.
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