Bendy, lightweight organic solar cells could be fast-tracked by new research

A breakthrough in the development of organic solar cells – whose light and bendy abilities have seen them wrapped around wind turbines in a recent trial by Acciona – could deliver a much-needed boost in efficiency and push them further along the path to commercialisation.

Organic solar cells get their name from their composition, with ingredients including materials and elements found in plants and animals, and hold the promise of being lightweight, flexible, and cheap to make.

Standing in the way of their commercialisation, however, is the fact that they have not yet reached the sunlight-to-electricity efficiencies of their silicon-based counterparts.

Researchers from the University of Cambridge, in collaboration with experts from Canada, Belgium, New Zealand, and China, think they might be able to make up ground, however, with a way to move energy in organic materials up to 1000’s of times faster than before.

In a report published in journal Science Advances, the research team said the new movement mechanism, coined “transient exciton delocalisation” allowed energy to move and transfer to the surrounding electrical wires much faster than normal.

“This improvement is made possible by the quantum-mechanical nature of reality, where energy can exist in many places at once, simultaneously,” said first author Alexander Sneyd, a PhD student at Cambridge’s Cavendish Laboratory.

“By taking advantage of these quantum-mechanical elements which allow for highly-efficient energy movement, we can make better, more efficient solar cells.”

The effort started with a nanotechnology technique called “living crystallisation driven self-assembly,” which the team used to create nanofibres made from a sulphur and carbon-based polymer.

This then allowed the researchers to precisely control the position of each of the atoms in the organic nanofibre to create what they have described as a “perfect” model material.

“This was really the secret to the success,” said Dr. Akshay Rao of the Cavendish Laboratory who led the research. “We were able to attain an unprecedented level of structural control, which one could only dream of until very recently.”

The team then shone a laser at the nanofibers to mimic sunlight, and watched the energy move over time using a technique called transient-absorption microscopy to create ‘films’ of the energy transport.

“When we performed the experiments, we were very surprised,” explained Sneyd. “The energy was moving at speeds of 100’s or even 1000’s of times faster than what was typically observed in the scientific literature.”

Finally, a supercomputer was employed to simulate – at the quantum level – what was occurring physically in the nanofibres. The results revealed that the ability for the energy to “delocalize,” or be in many places at the same time, was mainly responsible for the unexpected behaviour.

“This new mechanism provides many opportunities to significantly improve the performance of traditional organic solar cells,” said Professor Sir Richard Friend of the Cavendish Laboratory, who co-led the study.

“But even more excitingly, it’s also opening up prospects of whole new types of devices based on inexpensive and adaptable organic materials.