Solar cells are believed to be ideal in harvesting renewable energy, but researchers are trying to work out some of the device's kinks.
The highest-energy light falls into the ultraviolet and visible spectrums, but most solar energy is harvested from infrared light. Solar cells often absorb this infrared light, but tend to waste a majority of the energy-rich visible light, a University of Cambridge news release reported.
"We began by going back to fundamentals; looking at the solar energy challenge from a blue skies perspective," Doctor Brian Walker, a research fellow in the Cavendish Lab's Optoelectronics group, who led the study, said.
An absorbed photon creates a "single electronic excitation that is then separated into an electron and a positively charged hole, irrespective of the light energy," the news release reported.
Researchers believe splitting these photons into two could double the cells current, making it more energy efficient.
Researchers observed as the "initial electronic excitation" split into a pair of "half energy excitations." This phenomenon can be observed in certain organic molecules when the quantum mechanical effect of electron spin sets the initial spin 'singlet' state to be double the energy of the alternative spin 'triplet' arrangement."
This new study suggests the singlet fission process in triplets is extremely dependent on how molecules interact.
The team looked at different material dilutions to make their findings. When the molecules were farther away (dilute) they did not undergo singlet fission; but when they were closer together (concentrated) the colliding molecules caused the fission. The researchers found that as soon as two molecules collided the singlet fission became "extremely efficient," and caused every photon to "produce two triplets."
"Singlet fission offers a route to boosting solar cell efficiency using low-cost materials. We are only beginning to understand how this process works, and as we learn more we expect improvements in the technology to follow," Walker said.
The team conducted laser and chemical experiments to test the processes reactions, this allowed the team to observe a step in fission that had never been observed before.
"Very few other groups in the world have laser apparatus as versatile as ours in Cambridge," added Andrew Musser, a researcher who collaborated in the study, said. "This enabled us to get a step closer to working out exactly how singlet fission occurs."
The team hopes scientists will be able to use their findings to create new solar material.
