UNSW Researchers Claim Solar Cell Breakthrough – CleanTechnica

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In a blog post entitled “Changing the rules: UNSW breakthrough opens door to silicon cells beyond 30% efficiency with singlet fission,” the Australian Center for Advanced Photovoltaics said, “A team from UNSW Sydney has published a major advance that could unlock a new generation of high efficiency silicon solar cells — using singlet fission. The researchers demonstrate, for the first time, that a new class of stable organic molecules can be integrated with silicon to boost efficiency, while reducing heat and extending panel lifetime.”

It explains that most solar cells today convert one absorbed photon into a single electron/hole pair, but singlet fission allows one high energy photon to generate two excited electron/hole pairs, which has the effect of doubling the electrical yield from the bluest part of the solar spectrum. “Theoretical models suggest that adding a singlet fission layer could improve silicon solar cell efficiency by more than 10 percent,” the Center claims.

The researchers said in their published report, “Significant steps have been made in the development of singlet fission silicon photovoltaics, but all examples reported to date use tetracene as the singlet fission material. Tetracene is photochemically unstable and therefore unsuitable for commercial applications.

“Here we demonstrate singlet fission-derived triplet exciton transfer to c-Si from photochemically stable dipyrrolonaphthyridinedione (DPND) derivatives, with a thin layer of tin oxide as the passivation layer. An overlayer of poly(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT:PSS) was found to improve interface passivation further. These observations demonstrate that singlet fission photovoltaic devices can be made using stable and commercially viable materials.”

Lead researcher Professor Ned Ekins-Daukes of the University on New South Wales said, “Crucially, we’ve developed a practical pathway to higher output silicon solar cells, without the cost and complexity of tandems, that industry can now trial.”

The UNSW reseaerch breakthrough builds on nearly 20 years of collaboration between three of the lead researchers — Professors Tim Schmidt and Ned Ekins-Daukes, and Assoc. Prof. Murad Tayebjee. Schmidt is a leading expert on the science of molecular singlet fission, while Ekins-Daukes is an expert in high-efficiency photovoltaics, and Tayebjee is an award-winning physical chemist and solar PV engineer.

Recent work by the team, published in Nature Chemistry in 2024, showed how the photo-luminescence emitted from the singlet fission is linked to the underlying molecular process. This means the light emitted can be used to monitor the process, creating a powerful diagnostic avenue for materials development and quality control in PV manufacturing.

Photons from sunlight that are within silicon’s bandgap are absorbed and generate one excited electron/hole pair per photon. Photons below silicon’s bandgap are not absorbed and do not generate electrons. High energy photons above silicon’s bandgap (blue and green wavelengths) are absorbed and create one electron but lose excess energy as heat.

When a singlet fission material is layered over a silicon cell, it captures the high-energy photons and splits each photo into two excitons that match silicon’s bandgap, and each form an electron/hole pair. This doubles the electrical yield from the blue, high-energy photons, and reduces the heat generation.

Solar & Singlet Fission

In its blog post, ACAP said that most current research into next-generation silicon solar cells involves tandem devices that have at least two junctions, requiring a redesign of the entire cell architecture. In contrast, singlet fission on silicon solar cells can be built upon silicon technologies with minimal changes to the silicon architecture.

The commercial implications are far reaching. Silicon modules today typically achieve 20 to 25 percent efficiency. Singlet fission could lift that figure beyond 30 percent, meaning fewer panels would be needed for the same energy output. That in turn would lower overall system costs and make applications in space-constrained rooftops, electric vehicles, and building-integrated photovoltaics feasible.

By harvesting energy that would otherwise turn to heat, singlet fission reduces silicon cell operating temperatures. Lab and modelling studies suggest panels could run 2.4°C cooler, extending lifetime by around 4.5 years. The benefit there is lower replacement costs and an increase in the value of long-term power purchase agreements.

Dr. Jessica Yajie Jiang of UNSW said, “For manufacturers, the attraction is clear — more energy from the same module materials, plus cooler running that extends lifetime. We’re now moving from elegant science to practical solar products, and the impact for industry, investors, and the environment could be profound.”

Murad Tayebjee, who was one of the primary researchers, added that, “We can now read the light signatures of singlet fission with unprecedented clarity. This opens the door to discovering and optimizing a wide range of new materials that could one day boost the efficiency of silicon solar cells.”

Studying 30 Year Old Solar Panels

Solar panels are also in the news this week because of a study published in the journal EES Solar which finds that panels installed at various locations in Switzerland 30 years ago are still producing 80 percent of their original power. According to Chemistry World, the study found panel performance declined by just 0.24% per year on average — three times slower than expected. “This [data] really shows that photovoltaics can last [longer than expected], and it’s an important message to the photovoltaic industry,” says lead researcher Ebrar Özkalay at the University of Applied Science and Arts of Southern Switzerland.

The researchers found that altitude and climate influence the lifetime of panels. The performance of panels at lower altitudes decreased at a faster rate. Those panels often reach surface temperatures of up to 80°C, increasing thermal stress from daily and seasonal temperature variations.

While the research is good news for the industry, it also highlighted the importance of using high quality materials and production techniques. Modern photovoltaic systems often prioritize higher efficiencies and reduced costs, which leads manufacturers to use thinner and lower quality materials. But the team behind the study suggests that strategy may compromise the long term reliability of the panels.

“The bill of materials — everything that goes into a panel — has a great influence on performance, even when made by the same company,” said Dirk Jordan, a photovoltaics expert at the National Renewable Energy Laboratory in the US. “We can learn from these old panels to make future ones last, hopefully, as long.”

Commercial-scale solar panel production is still a fairly young industry, which means we are still learning from real-world experience. New technological breakthroughs, such as the one from UNSW, are happening on a regular basis, but experience with older panels can still inform manufacturers about how to make panels that last for 30 years or more. For parts of the world that do not have policies in place that suppress solar installations, the future truly is bright.