Limited efficiency, difficult to recycle— the expansion of photovoltaics has hit a roadblock. Christoph Brabec, Ian Marius Peters, and Verena Tiefenbeck have joined forces to change that.
Christoph Brabec is on the quest for the perfect material. More precisely, he’s searching for the ideal material for the solar modules of the future. “Silicon dominates the market,” he says, “but we are aware of the limitations of this technology.” These limitations lie partly in performance—more than 30 percent efficiency is theoretically unattainable. Moreover, silicon modules can only be used on roofs and open spaces because they are rigid, heavy, and do not allow light to pass through.
Brabec, a professor specializing in electronic materials and energy technology at FAU (Friedrich-Alexander-Universität Erlangen-Nürnberg) and Director at the Helmholtz Institute in Erlangen-Nürnberg (HI ERN), is researching alternatives, particularly organic photovoltaics. “We can directly print organic semiconductors onto thin substrates, simplifying production and consuming significantly less energy,” explains the Austrian-born researcher. “Since organic PV modules can be flexible and transparent, they can be integrated into facades, used indoors, or deployed as coverings over fields under which plants can grow.”
The pursuit of the perfect semiconductor material often involves compromises. Polymers with long molecular chains, for instance, are durable and resistant to temperature but are structurally limited in efficiency, especially in low-light conditions. On the other hand, short-chain molecules generate more power but have a shorter lifespan. Recently, Brabec and his team identified an oligomer as a strong candidate for organic PV, combining both efficiency and robustness.
Additionally, they are developing polymers that act not as active semiconductors but as passive protective layers, particularly in perovskite solar cells. Perovskites are metallic crystals with excellent optoelectronic performance and are easier to process than silicon but highly susceptible to corrosion. The polymer layers aim to shield against this while allowing the released electrons to pass through unhindered.
Such achievements are not feasible without intricate fine-tuning of the atomic structure. This isn’t a straightforward process—trial and error are the norm, not the exception. The goal at HI ERN is to automate these experiments. “We aim to map all processes—from material selection to test cycles—in a kind of digital twin,” says Brabec. “Through AI-driven development, we aim to avoid many repetitive steps and hope for faster breakthroughs in this crucial technology.”
Performance isn’t everything
Performance and durability aren’t the only criteria for the ideal solar module. “We shouldn’t get caught up only in the pursuit of maximum efficiency,” says Ian Marius Peters, research group leader at HI ERN. It’s crucial that PV modules, across all components and throughout their lifecycle, leave the smallest possible ecological footprint.
It starts with the choice of the semiconductor layer: a photoactive polymer, synthesized in a few steps, might be preferable to a material that, despite requiring more work and energy in the production process, yields just two percent more power. “For us, it’s also crucial to process the polymer without toxic and environmentally harmful solvents,” explains Peters. Therefore, cheaper and eco-friendly synthesis processes—such as deposition from aqueous solutions and inkjet printing—are a central focus of research at HI ERN.
Peters’ Cradle-to-Cradle approach naturally involves considering what happens to the products after their lifecycle ends. “Silicon modules, while having a longer lifespan, are hardly recyclable,” he says. “Mostly, they’re shredded and end up in landfills.” The solution lies either in a multi-layer design, making it easier to separate and recycle different materials, or in manufacturing the entire module consistently using organic materials that ideally can compost. “A module doesn’t have to last 100 years if the technology becomes outdated after 20 years,” explains Peters, who won a two-million-euro ERC Consolidator Grant for his research in 2023.
Technology needs acceptance
A holistic view of the ecological footprint could also enhance consumer acceptance, especially since choosing solar modules is essentially a decision for green energy. Verena Tiefenbeck investigates such consumer preferences and the market opportunities arising from them. As a professor of Digital Transformation at FAU, she closely examines the interface between companies and consumers. She explores how new products and technologies are adopted and integrated into everyday life. “Solar technology is a disruptive innovation,” she says. “So far, we have little data and limited choices and comparisons as users.”
Tiefenbeck attempts to glimpse into the future and sketch scenarios for various conditions, primarily based on policy decisions such as subsidy programs, bans on environmentally harmful products, or guidelines regarding recyclability. “In macroeconomics, these are referred to as shocks,” she explains. “Shocks can be dramatic but can also help new technologies break through.”
Apart from policy interventions, several other factors influence the market opportunities and sustainability of products. Dependency on raw materials is one such factor. “The more materials we import from other countries, the less predictable the medium- and long-term price developments become,” she explains. “Moreover, geopolitical instabilities can lead to supply shortages.” The societal acceptance of a technology also depends significantly on where and under what conditions the raw materials are sourced. Therefore, carbon-based electronics and photovoltaics offer hope: they are not only more ecological but also completely free from rare earths or precious metals.
Prof. Dr. Christoph Brabec studied theoretical physics at the University of Linz and received his doctorate there in 1995. After stints at the University of California, USA, and the University of Linz, Brabec became a leading research scientist at Siemens Technology in Erlangen. He later held leadership positions at Konarka Technologies, a leading manufacturer of organic photovoltaics. Since 2009, Brabec has been the Chair of Materials of Electronics and Energy Technology at FAU and, since 2018, the Director at the Helmholtz Institute Erlangen-Nürnberg (HI ERN). Christoph Brabec is among the most cited material researchers globally.
Dr. Ian Marius Peters studied physics at the University of Freiburg and completed his doctoral thesis on Photonic Concepts for Solar Cells there in 2009. He then conducted research at the Fraunhofer Institute for Solar Energy Systems (ISE) in Freiburg and the Solar Energy Research Institute of Singapore (SERIS). From 2014 to 2019, Peters was the team leader for silicon systems at the Massachusetts Institute of Technology (MIT), USA. Since 2019, he has been leading the research group “High-Throughput Characterization and Modeling for PV” at the Helmholtz Institute Erlangen-Nürnberg for Renewable Energies (HI ERN). In 2023, he received an ERC Consolidator Grant for his research on solar module recycling.
Prof. Dr. Verena Tiefenbeck studied mechanical engineering and management at the Technical University of Munich and the Ecole Centrale Paris, France. She then worked as a visiting researcher at the Massachusetts Institute of Technology (MIT) and a scientific staff member at the Fraunhofer Center for Sustainable Energy Systems (CSE) in Cambridge, USA