Fresh Insight into Enhancing Solar Cell Efficiency

Fresh Insight into Enhancing Solar Cell Efficiency

by Simon Mansfield

Sydney, Australia (SPX) Jul 29, 2024

Researchers are advancing the efficiency of next-generation solar cells by incorporating a technique that divides light particles, or photons, into smaller components.

In a study published in Nature Chemistry, scientists have explored the process of singlet fission, where light particles split, and its underlying mechanisms.

Professor Tim Schmidt from UNSW Sydney’s School of Chemistry, who has studied singlet fission for over ten years, suggests that this process could enhance the efficiency of current silicon solar cell technologies.

“Today’s solar cells work by absorbing photons which are then sucked away to the electrodes to do the work,” Prof. Schmidt says. “But as part of this process, a lot of this light is lost as heat. Which is why solar panels don’t run at full efficiency.”

Most photovoltaic solar panels today are made from silicon. Co-author Professor Ned Ekins-Daukes from UNSW’s School of Photovoltaics and Renewable Energy Engineering notes that while this technology is cost-effective, it is approaching its performance limits.

“The efficiency of a solar panel represents the fraction of energy supplied by the sun that can be converted into electricity,” Prof. Ekins-Daukes says. “The highest efficiency was set earlier this year by our industrial collaborator, LONGi. They demonstrated a 27.3 per cent efficient silicon solar cell,” he says. “The absolute limit is 29.4 per cent.”

Prof. Schmidt emphasizes the complexity of understanding how singlet fission works, particularly the transformation of one photon into two. “Our study addresses the route of this process. And we used magnetic fields for the interrogation. The magnetic fields manipulate the wavelengths of emitted light to reveal the way that singlet fission occurs. And that hasn’t been done before.”

Different colors of light have photons with varying energies. Regardless of the light’s energy, the cell receives the same energy, with any excess converted to heat, Prof. Schmidt explains. “So, if you absorb a red photon then there’s a bit of heat,” Prof. Schmidt says. “With blue photons, there’s lots of heat. There is a limit on efficiency for solar cells.”

Introducing singlet fission could significantly enhance silicon cells’ potential. “Introducing singlet fission into a silicon solar panel will increase its efficiency,” Prof. Ekins-Daukes says. “This enables a molecular layer to supply additional current to the panel.” The process divides the photon into smaller energy units that can be used individually, maximizing the higher energy part of the spectrum and reducing heat loss.

Last year, the Australian Renewable Energy Agency (ARENA) selected UNSW’s singlet fission project for their Ultra Low Cost Solar program. This initiative aims to develop technologies that achieve over 30 percent efficiency at a cost below 30 cents per watt by 2030. The team used a single wavelength laser to excite the singlet fission material and applied magnetic fields with an electromagnet to slow the process, making it easier to study.

“With this firm scientific understanding of singlet fission, we can now make a prototype of an improved silicon solar cell and then work with our industrial partners to commercialise the technology,” Prof. Ekins-Daukes says. “We’re confident we can get silicon solar cells to an efficiency above 30 per cent,” Prof. Schmidt says.

Research Report:Magnetic fields reveal signatures of triplet-pair multi-exciton photoluminescence in singlet fission