Researchers from the University of Turku, Finland, have found a new way to protect solar cells from harmful UV radiation using natural materials.
Their study, published in ACS Applied Optical Materials, shows that nanocellulose treated with red onion dye can effectively block UV rays while still allowing sunlight to pass through.
Why do solar cells need UV protection?
Solar cells can get damaged over time due to exposure to UV rays.
Most solar panels today use plastic films made from petroleum-based materials, such as polyvinyl fluoride (PVF) and polyethylene terephthalate (PET), to shield them from UV radiation.
However, researchers are looking for eco-friendly alternatives to replace these plastic-based films.
How does nanocellulose work?
Nanocellulose is made by breaking down plant-based cellulose into tiny fibers. It can then be treated with different substances to improve its ability to block UV rays.
In this study, researchers tested four types of bio-based protective films: nanocellulose treated with red onion skin extract, lignin, and iron ions. Among these, the red onion dye-treated film was the best at blocking UV radiation.
The study found that this natural UV filter blocked 99.9% of UV rays up to 400 nanometers, performing even better than commercial PET-based filters used today.
Preserving light for energy production
While UV protection is important, solar cells also need to receive enough visible and infrared light to generate electricity.
Some natural UV-blocking materials, like lignin, are too dark in color and reduce light transmission. However, the red onion dye-treated film allowed more than 80% of visible and infrared light (650–1,100 nm) to pass through, making it ideal for solar energy applications.
To test durability, the UV filter films were exposed to artificial sunlight for 1,000 hours, which is equal to about a year of natural sunlight in Europe.
The red onion-treated film maintained its UV protection and light transmission over time, while other bio-based filters, such as those treated with iron ions, lost effectiveness.
These findings could help improve not only dye-sensitized solar cells but also other types, such as perovskite and organic photovoltaics. The research team hopes to create fully biodegradable solar cells in the future, which could be used in electronics, such as sensors in food packaging.
This study is a step toward making solar energy more sustainable by using natural materials instead of plastics. With growing interest from the forest and electronics industries, bio-based solar cell components could become a reality in the near future.
