A project aimed at boosting Germany’s textile industry has led to the development of pliable, textile-based solar cells that could be used on buildings and lorries.
Fraunhofer researchers and their partners envision the thin-film photovoltaics being used on lorry tarpaulin to generate the electricity consumed by the driver on the road or parked up for the night. Similarly, building facades could be covered with photovoltaic textiles in place of concrete render.
Key to this advance is the use of textile industry processes to fabricate the pliable devices, which has brought Fraunhofer Institutes and partners together under the PhotoTex project to find viable solutions.
“There are a number of processes that enable solar cells to be incorporated in coatings applied to textiles,” said Dr Lars Rebenklau, group manager for system integration and electronic packaging at the Fraunhofer Institute for Ceramic Technologies and Systems (IKTS).
“That might sound easy,” added Dr Jonas Sundqvist, group manager for thin-film technology at Fraunhofer IKTS, “but the machines in the textile industry are designed to handle huge rolls of fabric – five or six meters wide and up to 1000m in length. And during the coating process, the textiles have to withstand temperatures of around 200 °Celsius.
“Other factors play a key role too: the fabric must meet fire regulations, have a high tensile strength and be cheap to produce.”
To fulfil these specs the consortium opted for a glass-fibre fabric.
According to Fraunhofer, the team also faced the challenge of how to apply the wafer-thin bottom electrode, the photovoltaic layer and the top electrode to the fabric. The solution was to use transfer printing to apply a layer that levels out the peaks and troughs on the surface of the fabric.
Other processes have been adapted so that they can be incorporated in standard production methods used in the textile industry. To that end, the two electrodes – which are made of electrically conductive polyester – and the photovoltaic layer are applied via the roll-to-roll method. The solar cells are also laminated with an additional protective layer to add robustness.
“This has demonstrated the basic functionality of our textile-based solar cells,” Rebenklau said in a statement. “Right now, they have an efficiency of between 0.1 and 0.3 per cent.”
In a follow-up project, the team hope to increase this over five per cent. The team acknowledge that silicon-based solar cells are more efficient but add that their efforts offer an alternative for specific applications. If successful, the first textile-based solar cells could be ready for commercialisation in around five years.
Fraunhofer IKTS worked on the project in collaboration with the Fraunhofer Institute for Electronic Nano Systems ENAS, Sächsisches Textilforschungsinstitut, and industrial partners including erfal, PONGS Technical Textiles, Paul Rauschert, and Gilles Planen.