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Organic solar cells in a spin

Organic solar cells in a spin

Manipulating the ‘spin’ of electrons in organic solar cells can drastically improve their performance, say researchers from Cambridge and Washington. Their findings may have implications in cheap, high performing solar power technologies.

“This discovery is very exciting, as we can now harness spin physics to improve solar cells, something we had previously not thought possible,” said lead author Dr Akshay Rao, a research fellow at the Cavendish Laboratory and Corpus Christi College, Cambridge.

Organic solar cells mimic photosynthesis using large, carbon-based molecules to harvest sunlight rather than the inorganic semiconductors used in commercial solar cells. Organic cells can be very thin, light, and highly flexible and can even be 3D-printed, so they represent faster and cheaper production processes than current solar cells. However, consistency between different carbon-based molecules used for organic solar cells has been a major issue until now.

Roa’s team developed sensitive laser-based techniques to track the motion and interaction of electrons in organic solar cells and found the performance differences between materials could be attributed to the quantum property of spin.

Spin is a property of particles related to their angular momentum, with electrons coming in two phases, ‘spin-up’ or ‘spin-down’. Electrons in solar cells can be lost through a process called ‘recombination’ where electrons lose their excitation and fall back into an empty state known as the ‘hole’.

The researchers discovered that by arranging the electrons’ ‘spin’ in a specific way, they can block the energy collapse from recombination and increase current in the cell.

The team believe that the findings could influence design concepts that could help close the gap between organic and silicon solar cells. These designs could also be applied to Organic Light Emitting diodes which provide more efficient displays in mobile phones and televisions.

Dr Simon Gélinas, a co-author, also from the Cavendish Laboratory said: “Through this, we’ve identified what mechanisms prevent the loss of electrical current in good organic solar cells. Now we can design materials knowing specifically how to harvest the most out of this process.”

The findings are published in Nature.



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