Researchers at UNSW Sydney have made significant strides in solar technology by developing a method that could double the energy output from sunlight. This advancement, centered around a process known as singlet fission, allows a single photon to split into two packets of energy, enhancing the efficiency of solar panels. The findings from the UNSW team, dubbed the Omega Silicon group, are promising in the quest to make solar energy cheaper and more effective.
In their recent study, the researchers demonstrated how singlet fission can be applied to organic materials that could potentially be mass-produced for solar panel use. “A lot of the energy from light in a solar cell is wasted as heat,” explained Dr Ben Carwithen, a postdoctoral researcher at UNSW’s School of Chemistry. “We’re finding ways to take that wasted energy and turn it into more electricity instead.”
Breaking Through Efficiency Barriers
Currently, most solar panels are constructed from silicon, which is affordable and reliable but has limits. The best commercial silicon cells convert approximately 27% of sunlight into electricity, with a theoretical maximum of 29.4%. The introduction of singlet fission offers a pathway to exceed this barrier. When sunlight interacts with certain organic materials, one high-energy photon can create two lower-energy excitations, effectively producing two usable packets of energy.
“Integrating singlet fission into a silicon solar panel will increase its efficiency,” stated Professor Ned Ekins-Daukes, project lead and head of UNSW’s School of Photovoltaic & Renewable Energy Engineering. The challenge has been identifying a suitable material, as previous research utilized a compound called tetracene, which degraded quickly in the presence of air and moisture.
The UNSW team has now identified a compound called DPND (dipyrrolonaphthyridinedione), which maintains stability under real-world conditions while facilitating singlet fission. “We’ve shown that you can interface silicon with this stable material, which undergoes singlet fission, and then injects extra electrical charge,” Dr. Carwithen noted.
Innovating for Future Solar Applications
The core principle of this research is to maximize the utilization of the Sun’s energy. The team’s work builds on over a decade of fundamental research led by Professor Tim Schmidt, who pioneered the use of magnetic fields to elucidate the singlet fission pathway. “Our previous study addressed the route of this process,” Professor Schmidt remarked. “We used magnetic fields to manipulate the emitted light and reveal how singlet fission occurs. This hadn’t been done before.”
By comprehensively understanding the underlying physics, the researchers can design improved materials and layered structures to enhance efficiency. “Different colours of light carry different energies,” Professor Schmidt explained, emphasizing that blue light, which holds more energy, is often lost as heat in traditional solar cells. “With singlet fission, that excess energy can be turned into usable electricity instead.”
This project has garnered attention as a significant advancement for solar technology, according to Associate Professor Murad Tayebjee, who stated that this is “the first demonstration of singlet fission on silicon using a relatively stable organic molecule based on industrial pigments.” These pigments are durable and do not degrade over time, making them suitable for solar applications.
The innovative technology involves adding an ultra-thin organic layer to traditional silicon cells. “In principle, it’s just painting an extra layer on top of the existing architecture,” Dr. Carwithen said. The theoretical maximum efficiency for solar panels utilizing singlet fission is around 45%, representing a significant improvement over current technologies. “Pushing towards 30% would already be fantastic,” he added, “but there’s a higher ceiling we can hopefully reach.”
The research is part of a broader national initiative to enhance solar power affordability and efficiency. In March 2023, the Australian Renewable Energy Agency (ARENA) selected UNSW’s singlet fission project for its Ultra Low Cost Solar program, which aims to produce solar panels with over 30% efficiency at costs below 30 cents per watt by 2030.
The Omega Silicon team has caught the attention of seven of the world’s largest solar companies. “We have industry partners waiting in the wings,” Dr. Carwithen stated. “They’re ready to help commercialise this if we can show it works in the lab.” He anticipates that a small-scale proof of concept could be ready within the coming years, though he acknowledges the unpredictable nature of scientific progress. “There could be a big breakthrough next week and everything clicks,” he noted, “but a more realistic timeline is five years.”
This collaborative effort involves a multidisciplinary research team from various UNSW schools, including chemistry, physics, and photovoltaics, showcasing the integration of diverse expertise to drive innovation in solar energy technology.
