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Researchers develop bio-based UV filter with nanocellulose and red onion, outperforming conventional materials in protection and transparency for solar cells
Researchers have developed a bio-based ultraviolet (UV) protective film that could replace conventional materials derived from oil in solar cells. The study, led by the University of Turku in Finland in partnership with Aalto University and Wageningen University, represents the first comprehensive analysis comparing different bio-based UV filters and their long-term effectiveness.
Solar cells are highly vulnerable to degradation caused by UV radiation. To prolong their lifespan, protective films are required. Conventional materials used in these coatings include petroleum-based compounds such as polyvinyl fluoride (PVF) and polyethylene terephthalate (PET).
However, the search for sustainable alternatives has led scientists to explore nanocellulose, a nanoscale biopolymer.
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Eco-friendly alternative outperforms conventional filters
The researchers modified nanocellulose with specific compounds to improve UV protection without compromising transparency. One of the most significant advances came from infusing the material with red onion skin extract.
The study revealed that nanocellulose films enriched with this extract achieved 99,9% UV absorption at wavelengths up to 400 nanometers, outperforming PET-based filters.
PhD researcher Rustem Nizamov from the University of Turku highlighted the potential of these materials. “Nanocellulose films treated with red onion dye are a promising option in applications where the protective material must be bio-based”, He stated.
Comparing Different UV Filters
The team tested four distinct types of nanocellulose films modified with different substances, including red onion extract, lignin and iron ions.
The results showed that the filter enriched with red onion offered the best UV protection. In addition, it managed to balance UV protection and transparency, an essential factor for the efficiency of solar cells.
UV radiation is harmful to solar cells, but visible and near-infrared light (between 700 and 1.200 nanometers) are essential for photovoltaic conversion. The big challenge is to develop materials that block harmful radiation without reducing the light transmission needed for power generation.
Lignin, for example, has been shown to be ineffective in this balance. Although it has good UV-blocking properties, its dark brown coloration impairs optical transparency.
In contrast, red onion-treated films maintained more than 80% light transmission between 650 and 1.100 nanometers, making them a promising alternative for photovoltaic coatings.
Durability testing and future applications
To assess the stability of the bio-based UV filters, the researchers performed accelerated aging tests. The materials were exposed to artificial light for 1.000 hours, simulating a year of outdoor sun exposure in a European climate.
During this period, digital images were used to monitor visual changes in the protective films and solar cells.
According to Nizamov, the tests highlighted the importance of long-term assessment. “The study emphasized the importance of long-term testing for UV filters, as the UV protection and light transmittance of other bio-based filters changed significantly over time. For example, films treated with iron ions had good initial transmittance, which reduced after aging”, He explained.
The films were tested on dye-sensitized solar cells, one of the technologies most vulnerable to UV-induced degradation. However, the scientists believe the findings could be applied to other photovoltaic technologies, such as perovskite cells and organic solar cells.
Expansion into new areas
The study also suggests that these UV filters could be used in other applications that require protection from ultraviolet radiation.”These results are also relevant for the UV protection of other types of solar cells, as well as any application where the use of a bio-based UV filter is paramount.”, Nizamov added.
The next steps in the research include integrating biodegradable components into solar cells, aiming to create sustainable energy technologies.
Among future possibilities, researchers highlight the development of self-powered sensors for food packaging and transient electronic devices.
Professor Kati Miettunen, a specialist in materials engineering, highlighted the interest of the forestry industry in advancing this research. “The forestry industry is interested in developing new high-quality products. In the field of electronics, these can also be components for solar cells.", said.
With the positive results, nanocellulose modified with red onion dye emerges as a viable option to increase the efficiency and durability of solar cells, reducing dependence on petroleum-derived materials.
With information from Interesting Engineering.
