University of New South Wales (UNSW) engineers have improved the performance of solar cells made from antimony chalcogenide, reaching a champion power conversion efficiency of 11.02% in the laboratory and a certified efficiency of 10.7%.
Due to its optoelectronic properties, high absorption coefficient, material availability, and ability to be deposited at low temperatures, which supports large-scale, low-cost production, antimony chalcogenide (Sb2(S,Se)3) has emerged as a promising alternative for next-generation PV materials, especially in the pursuit of ultrathin and tandem solar technologies.
Despite its advantages, the efficiency of antimony chalcogenide had not progressed beyond 10% since 2020. But during this latest research, the UNSW team found the major problem was being caused by the elements that make up the material — sulfur and selenium — not being distributing evenly as it was being produced.
Dr Chen Qian, the first author of the research paper, said this uneven distribution created an “energy barrier” that was making it harder for the electrical charge generated by the sunlight to move through the solar cell.
“It was like driving a car up a steep slope. If you do that, you need to use more fuel to get to the end, whereas if the road is flat it’s more efficient to reach there,” he said. “When the distribution of the elements inside the cell is more even, then the charge can move more easily through the absorber rather than being trapped before they are collected, which means more sunlight is converted into electricity.”
To address the issue, the researchers introduced a small amount of sodium sulfide as an additive in the precursor solution to control reaction kinetics.
The UNSW team said this strategy enables a more uniform depth-dependent elemental distribution, flattens the unfavourable valence band maximum gradient across the depth and suppresses the formation of deep-level defects.
Image: UNSW, Chen Qian
The improved antimony chalcogenide solar cells reached a power conversion efficiency of 11.02% in UNSW laboratory with a certified value of 10.7% independently verified by the CSIRO.
The UNSW researchers acknowledge that further work is required to reduce defects inside the material but said they are confident that can be achieved through chemical treatments known as passivation.
“In the next few years we will continue to work on reducing the defects in this material via that passivation process,” Qian said. “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.”
UNSW School of Photovoltaic and Renewable Energy Engineering Scientia Professor Xiaojing Hao, who led this research, said the progress marks a major step forward in the development of antimony chalcogenide as a solar cell candidate.
“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,” she said.
“Each layer absorbs different parts of the sunlight to make more electricity. What researchers around the world are trying to work out is what material is best to use as the top cell, in partnership with a traditional silicon cell.”
“Each material has its own pros and cons, and I don’t think there is an ideal top cell candidate yet. We need more top cell candidates that can partner with silicon cell. Antimony chalcogenide is one of those and very positive, especially given its distinct properties.”
The details of the study appear in “Regulation of hydrothermal reaction kinetics with sodium sulfide for certified 10.7% efficiency Sb2(S,Se)3 solar cells,” published in nature energy.
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