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Researchers Develop Biological-Based UV Filter With Nanocellulose and Red Onion, Surpassing Conventional Materials in Protection and Transparency for Solar Cells
Researchers have developed a biological-based ultraviolet (UV) protective film that can replace conventional petroleum-derived materials in solar cells. The study, conducted by the University of Turku in Finland, in partnership with Aalto University and Wageningen University, represents the first comprehensive analysis comparing different biological-based UV filters and their long-term effectiveness.
Solar cells are highly susceptible to degradation caused by UV radiation. To prolong their lifespan, protective films are necessary. The 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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Ecological Alternative Surpasses Conventional Filters
The researchers modified the nanocellulose with specific compounds to enhance UV protection without sacrificing transparency. One of the most significant advancements came from infusing the material with red onion skin extract.
The study revealed that nanocellulose films enriched with this extract achieved a UV absorption of 99.9% at wavelengths up to 400 nanometers, surpassing PET-based filters.
PhD researcher Rustem Nizamov from the University of Turku highlighted the potential of these materials. “Treated nanocellulose films with red onion dye are a promising option in applications where the protective material must be biologically based,” he stated.
Comparing Different UV Filters
The team tested four distinct types of modified nanocellulose films with different substances, including red onion extract, lignin, and iron ions.
The results showed that the filter enriched with red onion provided the best UV protection. Furthermore, it managed to balance UV protection and transparency, a key factor for the efficiency of solar cells.
UV radiation damages solar cells, but visible and near-infrared light (between 700 and 1,200 nanometers) are essential for photovoltaic conversion. The major challenge is to develop materials that block harmful radiation without reducing the necessary light transmission for energy generation.
Lignin, for instance, proved ineffective in this balance. While it has good UV blocking properties, its dark brown coloring impairs optical transparency.
In contrast, the films treated with red onion maintained over 80% light transmission between 650 and 1,100 nanometers, making it a promising alternative for photovoltaic coatings.
Durability Testing and Future Applications
To assess the stability of the biological-based UV filters, the researchers conducted accelerated aging tests. The materials were exposed to artificial light for 1,000 hours, simulating a year of outdoor solar 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 underscored the importance of long-term evaluation. “The study emphasized the importance of long-term testing for UV filters, as the UV protection and light transmittance of other biological-based filters changed significantly over time. For example, the films treated with iron ions had good initial transmittance, which decreased after aging,” he explained.
The films were tested on dye-sensitized solar cells, one of the technologies most vulnerable to UV-induced degradation. However, scientists believe that the findings could be applied to other photovoltaic technologies, such as perovskite cells and organic solar cells.
Expanding to New Areas
The study also suggests that these UV filters could be used in other applications that require protection against ultraviolet radiation. “These results are also relevant for UV protection of other types of solar cells, as well as any application where the use of a biologically based UV filter is paramount,” added Nizamov.
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, an expert in materials engineering, emphasized 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 could also be components for solar cells,” she said.
With positive results, nanocellulose modified with red onion dye emerges as a viable option to enhance the efficiency and durability of solar cells, reducing dependence on petroleum-derived materials.
With information from Interesting Engineering.
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