Erlangen, June 20, 2023 - Organic electronics can make a decisive contribution to decarbonization and at the same time help save rare and valuable raw materials. To achieve this, it is necessary not only to further develop manufacturing processes, but also to plan technical solutions for recycling already in the laboratory. Materials scientists at the Helmholtz Institute Erlangen-Nuremberg for Renewable Energy (HI ERN) and Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), together with British and US American research colleagues, are promoting this recycling strategy in the renowned journal "Nature Materials".
Organic electronic components, such as solar modules, have several outstanding properties: They can be applied in ultra-thin layers to flexible substrates and thus have a broader range of applications than crystalline materials. Since their photoactive substances are carbon-based, they also help to eliminate the need for rare, expensive and sometimes toxic raw materials such as iridium, platinum or silver.
Especially in the field of OLED technology, particularly for TV or computer screens, organic electronics is achieving enormous growth rates. "On the one hand, this is progress, but on the other hand, it also poses problems," says Prof. Dr. Christoph Brabec, Director of HI ERN and Chair of Materials Science (Materials of Electronics and Energy Technology) at FAU. The materials researcher sees a danger that an ecologically sensible technology such as organic electronics will be permanently integrated into a device architecture that is not sustainable overall. This applies not only to electrical devices, he says, but also to organic sensors in textiles, for example, which have an extremely short service life. Brabec: "Applied research in particular must now set the course for ensuring that electronic components leave the smallest possible ecological footprint in all individual components and over the entire life cycle."
A fundamental contribution to this is the further development of organic electronics itself: New materials and more efficient manufacturing processes can reduce production effort and energy consumption. "Compared to the synthesis of simple polymers, the production of the photoactive layer is many times more energy-intensive because it is evaporated at high temperature in a vacuum," explains Brabec. The researchers therefore propose establishing cheaper and more environmentally friendly synthesis processes - for example, deposition from water solutions and printing using an inkjet process. Says Brabec, "A major challenge here is to develop functional materials that can be processed without toxic and environmentally harmful solvents." In the case of OLED displays, inkjet printing also offers the opportunity to replace precious metals such as iridium and platinum with organic materials.
In addition to their efficiency, the operational stability of the materials is also crucial: In order to protect the vapor-deposited carbon layers of organic solar modules from environmental influences, complex encapsulation is necessary, which accounts for up to two-thirds of the total weight. More resistant material combinations could contribute to significant material, weight and energy savings here.
In order to realistically evaluate the ecological footprint of organic electronics, the entire product life cycle must be taken into account. If you look at the pure performance data, organic photovoltaics still lag behind conventional silicon modules - but three times less CO2 is emitted during their production. Striving for maximum efficiency isn't everything, Brabec says: "18 percent can be more ecologically sensible than 20 if the photoactive material can be produced in just five instead of eight synthesis steps."
The shorter lifespan of organic modules is also put into perspective on closer inspection: silicon-based photovoltaic modules may last longer, but they are virtually impossible to recycle. "Biocompatibility and biodegradability are becoming increasingly important criteria for both product development and packaging design," says Christoph Brabec. "We need to start considering recycling already in the laboratory." This means, for example, using substrates that are either easy to recycle or as easily degradable as the active substances. So-called multilayer designs, he says, can be used to ensure that different materials can be easily separated and recycled at the end of their product life. Brabec: "This cradle-to-cradle approach will be a crucial prerequisite for establishing organic electronics as an important component of the energy transition."
McCulloch, I., Chabinyc, M., Brabec, C. et al. Sustainability considerations for organic electronic products.
Nat. Mater. (2023).
https://www.nature.com/articles/s41563-023-01579-0
Director and Head of Research Department High Throughput Methods in Photovoltaics
