Researchers at the University of New South Wales (UNSW Sydney) have developed a groundbreaking method to observe how silicon solar cells degrade under ultraviolet (UV) radiation — and how they can naturally recover when exposed to sunlight. The findings, published in Energy & Environmental Science, provide new insights that could reshape how solar panels are tested, designed, and certified for long-term outdoor use.
The study, led by Scientia Professor Xiaojing Hao, along with Dr Ziheng Liu, Dr Pengfei Zhang, and Dr Caixia Li, introduces a non-destructive monitoring technique that allows scientists to track chemical changes inside operating solar cells at a microscopic level (UNSW Sydney, 2024).
Silicon solar cells are known to suffer ultraviolet-induced degradation (UVID), a process that can reduce performance by up to 10% after extended UV exposure, according to accelerated testing benchmarks. While previous research confirmed that cells can partially recover under normal sunlight, the exact material-level mechanisms behind this recovery remained unclear — until now.
Using ultraviolet Raman spectroscopy, the UNSW team was able to directly observe chemical bond changes near the surface of solar cells in real time. This technique works by analyzing how laser light scatters when it interacts with molecular structures, allowing researchers to identify changes in bonds involving hydrogen, silicon, and boron atoms.
According to Dr Ziheng Liu, the corresponding author of the study, this marks a major shift from traditional electrical-only measurements: “Instead of only measuring power output, we can now directly see how the material itself changes in real time, explaining the physical mechanism behind both degradation and recovery.”
The research revealed that UV exposure weakens critical surface bonds, reducing efficiency. However, when the cells are later exposed to visible sunlight, hydrogen atoms migrate back, broken bonds are repaired, and the material returns to its original structure — confirming that recovery occurs at the atomic level, not just electrically.
This discovery has important implications for the solar testing and certification process. Current accelerated ageing tests expose panels to intense UV radiation over short periods to simulate long-term outdoor use. But if some degradation effects are reversible under real sunlight, these tests may overestimate permanent performance losses.
“Distinguishing between reversible and permanent degradation is essential for accurate lifetime prediction,” Dr Liu noted.
Beyond research, the new monitoring method offers practical industry benefits. Unlike conventional UV tests that take weeks and may damage cells, the Raman-based technique can detect UV sensitivity in seconds — without harming the device. This makes it suitable for manufacturing quality control, material screening, and in-line inspection on production lines.
The study also helps explain why some solar cell designs degrade more than others, showing how surface coatings, passivation layers, and material choices influence hydrogen movement and long-term durability.
Supported by the ARC Research Hub for Photovoltaic Solar Panel Recycling and Sustainability (PVRS), the work provides a scientific foundation for improving solar panel reliability, optimizing cost-performance trade-offs, and refining industry testing standards.
As Prof. Xiaojing Hao summarized, the breakthrough brings the industry closer to more durable and accurately tested solar technologies: “With better monitoring tools, we can design better tests, better panels, and ultimately more reliable solar energy systems.”
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