In an endeavour to make solar energy cheaper and more efficient, a team of UNSW Sydney scientists and engineers have found a way to potentially double the energy obtained from traditional solar panels.
The process known as singlet fission shows how a single particle of light – a photon – can be split into two packets of energy, thereby doubling the electrical output in applications that involve harnessing solar energy.
“A lot of the energy from light in a solar cell is wasted as heat – which itself is also a form of energy,” UNSW’s School of Chemistry postdoctoral researcher Dr Ben Carwithen says.
“We’re finding ways to take that wasted energy and turn it into more electricity instead.”
Most solar panels are made from silicon. The limits to silicon’s efficiency mean that most of the cells currently convert about 27 percent of sunlight into electricity (the theoretical ceiling is 29.4 percent).
With singlet fission, when sunlight hits certain organic materials, one high-energy photon can produce two lower-energy excitations. Effectively, two packets of usable energy are produced instead of one.
The latest developments build on research led by Professor Tim Schmidt, head of UNSW’s School of Chemistry. His team was reportedly the first in the world to use magnetic fields to reveal a key part of the singlet fission pathway.
“Our previous study addressed the route of this process,” Schmidt says. “We used magnetic fields to manipulate the emitted light and reveal how singlet fission occurs.”
“Different colours of light carry different energies. Blue light has more energy, but most of that gets lost as heat in a normal solar cell. With singlet fission, that excess energy can be turned into usable electricity instead.”
The application of this new solar technology involves adding an ultra-thin organic layer to the top of a conventional silicon cell. Supervising author UNSW Associate Professor Murad Tayebjee says the latest research is the first demonstration of singlet fission on silicon using a relatively stable organic molecule based on industrial pigments, which don’t degrade over time. Those pigments provide colour, and colours absorb light.
Introducing singlet fission into a silicon solar panel enables a molecular layer to supply additional current to the panel. “In principle, it’s just painting an extra layer on top of the existing architecture,” Carwithen says. The theoretical limit for solar panels using singlet fission is around 45 percent efficiency. “Pushing towards 30 percent would already be fantastic,” he adds.
The Australian Renewable Energy Agency (ARENA) selected UNSW’s singlet fission project in 2023 for its Ultra Low Cost Solar program, which aims to deliver panels capable of more than 30 percent efficiency at less than 30 cents per watt by 2030.
The UNSW team working on this technology is known as Omega Silicon. Carwithen says solar companies are watching the Omega Silicon team closely and are ready to help commercialise this once the technology matures in the lab. “There could be a big breakthrough next week and everything clicks,” he says. “But a more realistic timeline is five years.”
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