MATERIALS | PHOTOVOLTAICS


Visual changes in the filter materials and solar cells were monitored using digital photography. The UV filter films were tested on dye-sensitised solar cells, which are vulnerable to wear by UV radiation. “These results are also relevant for UV protection


IMAGE: VÄINÖ ANTTALAINEN Above:


Nanocellulose film dyed with red onion skin extract gives effective UV protection


Onion protection Researchers at the University of Turku in Finland have used bio-based materials to make UV protection films for solar cells. Solar cells are prone to UV-induced degradation


and are often protected against it by petroleum- based films, such as those made of polyvinyl fluoride (PVF) and PET. The study – in collaboration with Aalto University


and Wageningen University in the Netherlands – found that nanocellulose dyed with red onion skin extract gives effective UV protection. The film protected 99.9% of UV radiation up to 400 nanome- tres. This UV filter outperformed even a commercial PET-based UV filter, which was used as a control. “Nanocellulose films treated with red onion dye


are a promising option in applications where the protective material should be bio-based,” said Rustem Nizamov, a doctoral researcher at the University of Turku. The study compared the durability and properties


of four types of protective film made from cellulose nanofibres. The nanocellulose films were treated with red onion extract, lignin, and iron ions – all of which have been found to block UV. The film treated with the red onion extract was the most efficient. The film treated with red onion dye exceeded 80% light transmission at longer wavelengths (650‒1,100 nanometres). The film also maintained its performance throughout the long testing period, said the researchers. Developing bio-based materials often involves a


trade-off between UV protection and light transmis- sion. Lignin, for instance, is a natural polymer with UV-absorbing properties but has a dark brown colour that limits its use in transparent films. The durability and performance of the filters was tested under artificial light for 1,000 hours, equiva- lent to about a year of sunlight in central Europe.


16 FILM & SHEET EXTRUSION | April 2026


of other types of solar cells, including perovskite and organic photovoltaics – as well as any applica- tion where the use of a bio-based UV filter is paramount,” said Nizamov. In future, the researchers plan to develop solar cell types that are biodegradable and can be used as power sources for sensors, such as in food packaging. The study was published in the journal ACS Applied Optical Materials.


New molecule Cambridge University scientists say they have identified a new organic molecule that could “transform solar energy harvesting”. “We are not just improving old designs, we are writing a new chapter in the textbook, showing that organic materials are able to generate charges all by themselves,” said Hugo Bronstein, co-author of a paper in Nature Materials. The research focuses on an organic semicon- ductor molecule called P3TTM which has “unique magnetic and electronic properties”. The team has created a solar cell from a P3TTM


film. When light hit the device, it achieved a ‘close-to-unity’ charge collection efficiency – mean- ing almost every photon of light is converted into a usable electrical charge.


In conventional semiconductor solar cells,


converting an absorbed photon into electricity can only happen at the interface between two different materials – with one acting as an electron donor, the other as an acceptor. However, the new materials can move an electron from one molecule to an identical neighbouring molecule, creating electrical charges. This means it may be possible to make solar cells from a single, low-cost lightweight material. “We are not just improving old designs,” said


Bronstein. “We are writing a new chapter in the textbook, showing that organic materials can generate charges by themselves.”


CLICK ON THE LINKS FOR MORE INFORMATION: � www.heliatek.com � www.basf.com � www.xfloat.co � www.chalmers.se � https://resou.osaka-u.ac.jp/en � www.utu.fi � www.phy.cam.ac.uk


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