Solar panels make an important contribution to the renewable energy supply, but solar panel waste is fast becoming a major problem. Now, in a study recently published in the Journal of Materials Chemistry A , researchers at the Nara Institute of Science and Technology (NAIST) have explored the science that could help increase the usefulness of easily mass-produced polymer-based solar cells.
Currently, about a third of the world's electricity comes from renewable sources. Silicon-based solar cells are the main contributor, but there is a growing problem: what to do with the panels after their 30-year lifespan. An article published in the May 2022 issue of Chemical & Engineering News lays out the problem: Even when businesses recycle frame and panel coatings, the most valuable, even toxic, materials are simply thrown away. It is estimated that 80 million metric tons of solar panel waste will be produced by 2050, which is a huge waste problem.
Polymer-based solar cells are a possible and cheaper solution. Such panels are thin and flexible and therefore, in principle, quite versatile. However, they have some problems; eg lower power conversion efficiency than silicon. "This efficiency is significantly limited by the fill factor: typically less than 60% even in high-end devices," said corresponding author Hiroaki Benten of the Nara Institute of Science and Technology. "The science behind the limited efficiency of all-polymer solar cells is still not well understood."
The revolutionary result of this research is the high filling factor: 70%, which remains at 60% even for polymer films with a thickness of several hundred nanometers. Competitive polymer technologies show a 40% fill factor at this thickness. Indeed, the bimolecular recombination of free electrons with free holes significantly slowed down the operation of the previous charge factor, but was suppressed in this work.
What bimolecular recombination is suppressed in polymer mixtures? "There is significant charge delocalization at the donor and acceptor sites," says lead author Masakazu Nakamura. "Proper assembly of the polymer donor and acceptor results in a highly ordered local structure of the polymer, which helps keep electrons from separating from holes."
Even if researchers solve the efficiency problem of all-polymer solar cells, they still need to extend the 10-year lifespan of the most advanced research prototypes. Additional research efforts include optimizing film morphology and even creating hybrid polymer-silicon solar cells to optimize energy harvesting and improve efficiency. In the coming years, solar cells may look and work much better than today's technology.
Courtesy of Nara Institute of Science and Technology.
Retrieved from : Enhancing the Efficiency of All-Polymer Solar Cells (October 3, 2022). Retrieved October 4, 2022, from https://techxplore.com/news/2022-10-efficiency-all-polymer-solar-cells.html.
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