Researchers at the University of Turku have developed a UV filter based on nanocellulose treated with red onion peel dye , capable of blocking up to 99.9% of ultraviolet rays .
This material represents an alternative to traditional coatings made from petroleum derivatives, such as polyethylene terephthalate (PET), and the use of plant extracts provides a more environmentally friendly and effective solution in long-term testing.
Technical advantages over a conventional UV filter
The red onion nanocellulose film maintains high transmissivity at visible and infrared wavelengths (650–1100 nm), exceeding 80% . This property is critical for solar cells to continue converting light into energy while protecting them from UV degradation.
In tests conducted over 1,000 hours of artificial exposure, the coating demonstrated structural stability and consistent effectiveness . In comparison, other biobased filters, such as those treated with lignin or iron ions, showed loss of transmissivity over time.
Applications in emerging solar technologies
UV protection is especially important in dye-sensitized solar cells, perovskites , and organic photovoltaics. These technologies, although promising, are more vulnerable to UV radiation.
The new plant-based coating could be key in the manufacture of biodegradable solar devices and self-powered sensors. It also offers an opportunity to integrate valuable products from agro-industrial waste.
Industrial horizon and scientific collaborations
The project, funded by the Finnish Research Council, involved Aalto University (Finland) and Wageningen University (Netherlands). The research was published in the journal ACS Applied Optical Materials .
The Solar Energy Materials and Systems (SEMS) group at the University of Turku is exploring industrial applications within the BioEST project. The Finnish forestry industry has already expressed interest in these solutions as part of its transition to higher-value-added products.
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Source and photos: University of Turku
