“This new mechanism provides many opportunities to significantly improve the performance of traditional organic solar cells. But even more excitingly, it’s also opening up prospects of whole new types of devices based on inexpensive and adaptable organic materials.”Sir Richard Friend, Cambridge University
Researchers have discovered a new, faster way in which organic materials can redistribute sunlight energy, which could lead to the next generation of organic solar cells for converting sunlight into electrical power and assist in the battle against climate change.
Most of today’s solar cells are made from silicon and are heavy, rigid and expensive to produce. By contrast, organic solar cells hold the promise of being lightweight, flexible and cheap to make. However, organic solar cells have not yet reached the sunlight-to-electricity efficiencies of their silicon-based counterparts, preventing their commercialization.
Now, researchers from the University of Cambridge in the UK, in a collaboration with colleagues in Canada, Belgium, New Zealand and China, have discovered a new fundamental way for energy to move in organic materials at speeds up to thousands of times faster than normal, which could help to realise the promise of organic photovoltaics. The researchers report their findings in a paper in Science Advances.
This new movement mechanism, termed 'transient exciton delocalization', allows energy to move and transfer to 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,” explained 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 research team began by using a highly advanced nanotechnology technique called ‘living crystallization driven self-assembly’ to create nanofibers made from a sulphur-and-carbon-based polymer. This allowed them to precisely control the position of each of the atoms in the organic nanofiber to create a ‘perfect’ model material.
“This was really the secret to the success,” said 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 used a technique called transient-absorption microscopy to observe the energy move over time, creating ‘films’ of energy transport. This allowed them to observe energy movement over extremely short timescales, with a resolution of almost a single femtosecond, which is equivalent to a film with a frame rate of 1 million billion frames per second.
“When we performed the experiments, we were very surprised,” said Sneyd. “The energy was moving at speeds of hundreds or even thousands of times faster than what was typically observed in the scientific literature.”
Finally, they used a supercomputer to simulate at the quantum level what was occurring physically in the nanofibers. By comparing the results of the simulation with the experiment they concluded that it was indeed the ability of the energy to ‘delocalize’, or be in many places at the same time, that was primarily responsible for the unexpected behaviour.
“This new mechanism provides many opportunities to significantly improve the performance of traditional organic solar cells,” said 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.”
This story is adapted from material from the University of Cambridge, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.