5 Minutes
Biodegradable UV filters: a new approach to greener solar technology
Solar photovoltaic devices are central to global decarbonization efforts, but their materials footprint is not entirely benign. Aside from the energy and materials used to produce panels, many solar cells require protective UV filters to shield sensitive layers—such as passivation coatings and silicon—from damaging radiation below ~400 nanometers. Commercial modules typically use petroleum-derived films like polyvinyl fluoride (PVF) and polyethylene terephthalate (PET) for that purpose. Those polymers are effective and widely recycled in large installations, but they are not ideal for small, single-use, or hard-to-recycle devices such as biodegradable microsensors.
Study overview: nanocellulose films and bio-based coatings
Researchers at the University of Turku and Aalto University (Finland), together with Wageningen University (Netherlands), explored a bio-based alternative: UV-protective films built from nanocellulose. Nanocellulose is a natural polymer derived from plant or bacterial sources and is the most abundant organic polymer on Earth. The team produced thin nanocellulose films and then applied different bio-derived coatings—lignin, iron ion treatments, and red onion extract—to evaluate UV-shielding performance and light transmission in wavelengths important for photovoltaic energy conversion.
The paper, published in ACS Applied Optical Materials, reports that red onion extract delivered the strongest UV attenuation tested—blocking roughly 99.9% of UV radiation in the tested band—and even exceeded the UV-blocking ability of commercial PET filters. At the same time, the red onion–treated films allowed substantial light transmission in the near-infrared and visible bands that drive power generation: about 80% transmission between roughly 650 and 1,100 nanometers, the spectral region critical for many silicon and next-generation cells.
Long-term performance and comparative results
An important element of the study was durability testing. The researchers ran accelerated light-exposure tests for about 1,000 hours (a proxy for roughly one year of sunlight exposure). Some coatings—especially iron-ion treatments—showed promising initial UV protection but degraded significantly during the test period. By contrast, the red onion–based films maintained both high UV attenuation and favorable light transmission over the full testing window, underscoring the need for long-duration trials when assessing UV filters for real-world use.
Rustem Nizamov, the study’s lead author at the University of Turku, noted that nanocellulose films dyed with red onion extract are an attractive candidate where a bio-based protective layer is required. He added that the results are relevant not only for silicon photovoltaics but also for perovskite and organic solar cells, which are typically more sensitive to UV damage and can benefit from biodegradable encapsulation options.
Scientific context and implications for solar sensors
Microscale solar-powered devices—environmental sensors, short-lived distributed electronics, and some remote-deployed instruments—stand to gain the most from fully biodegradable protective layers. Oil-based polymers are fine for large, centrally managed arrays that can be recycled, but distributed applications often lack such infrastructure. A UV filter that is both bio-derived and biodegradable reduces the environmental impact at end-of-life and could simplify deployment in sensitive ecosystems.
Beyond waste reduction, bio-based filters may open design possibilities for emerging photovoltaics. Perovskite and organic photovoltaics are promising for lightweight and flexible energy harvesting but suffer from stability challenges. A compatible, bio-derived filter that blocks harmful UV while transmitting energy-producing wavelengths could lengthen operational life without compromising sustainability.
Related technologies and future research directions
Key areas for follow-up include scaling extraction and processing of natural dyes, standardizing accelerated aging protocols, and integrating such films into full encapsulation stacks. Researchers will need to test weathering, moisture resistance, thermal cycling, and compatibility with adhesives and electrode materials. There are also supply-chain and cost questions: widespread adoption requires reliable, low-impact sources of nanocellulose and dye feedstocks.
Expert Insight
Dr. Elena Martinez, a materials engineer specializing in sustainable electronics (fictional), commented: “This study demonstrates that simple, non-toxic compounds from plants can match or exceed synthetic films for UV protection when combined with advanced substrates like nanocellulose. The challenge now is translating laboratory durability to outdoor deployments and ensuring consistent performance across seasons and climates. If that can be achieved, the environmental benefits for distributed sensors and transient electronics are significant.”
Conclusion
The Turku–Aalto–Wageningen study offers a compelling case for bio-based UV filters in niche photovoltaic applications. Nanocellulose films treated with red onion extract combined high UV attenuation with strong light transmission in the crucial energy-producing bands and retained performance during accelerated aging. While scale-up, long-term field validation, and integration into device stacks remain necessary next steps, this work points to a simple, nature-derived route to reducing the environmental footprint of solar-powered microsystems and next-generation photovoltaics.
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