A team of scientists and engineers at UNSW has developed a method to overcome one of the key efficiency limits in solar technology, using a process known as singlet fission.

Singlet fission allows one high-energy photon to split into two packets of energy, effectively doubling the electrical output of a solar cell. The UNSW team, known as Omega Silicon, demonstrated this using an organic compound that could be produced at scale for solar applications.

Most commercial solar panels use silicon, which has a practical efficiency limit of about 29.4%. Singlet fission offers a pathway beyond that ceiling by adding a molecular layer that supplies extra current to the silicon base.

Earlier materials like tetracene showed promise but were too unstable for real-world use. The UNSW team has shown that dipyrrolonaphthyridinedione (DPND) performs the same energy-splitting function while maintaining stability outdoors.

“We’ve demonstrated that silicon can be interfaced with a stable material that undergoes singlet fission and injects additional electrical charge,” Dr Ben Carwithen says.

“It’s an early step, but the first proof that this can work in a realistic system.”

The work builds on more than a decade of research by Professor Tim Schmidt, whose team was the first to use magnetic fields to map the singlet fission pathway. This deeper understanding allowed the researchers to design more efficient organic compounds and layer structures.

“In principle, it’s like painting an extra layer on top of existing panels. The architecture stays the same, we’re just making better use of the light,” Ben says.

The approach involves coating a conventional silicon cell with an ultra-thin organic layer and the theoretical efficiency limit of solar panels incorporating singlet fission is around 45%.

The research is part of the Australian Renewable Energy Agency’s Ultra Low Cost Solar program, which targets 30% efficiency at under 30 cents per watt by 2030.

With strong industry interest, a small-scale proof of concept could be achieved within the next five years.

“We have commercial partners ready to move when the technology is ready,” Ben says.

The project was led by a multidisciplinary UNSW team spanning chemistry, physics and photovoltaics, including Drs Matthew Brett, Alex Baldacchino, Shona McNab, Jingnan Tong and Victor Zhang.