Researchers give photovoltaic modules a nano "clothing" to completely transform their appearance.

To better meet the architectural aesthetic and visual requirements, it is necessary to refine or even customize the appearance of photovoltaic components used in buildings. The Fraunhofer Institute for Electron Beam and Plasma Technology (Fraunhofer FEP) in Germany has developed decorative films that utilize nanoimprint technology. These films can be attached to the outer surfaces of PV modules and can also be tailored to specific design needs, helping to break away from the uniformity that currently characterizes most PV components.
 

Freely combinable facade components covered with decorative film—on the left are photovoltaic modules, while on the right are metal facade elements without photovoltaic functionality. Source/Photo: Fraunhofer FEP, Finn Hoyer

The traditional approach to adjusting the appearance of photovoltaic modules involves making changes to either the front-glass panel or the encapsulant film of the module. While this method is well-suited for manufacturers with dedicated PV module production lines, it also comes with drawbacks such as a long supply chain, challenging material control, difficult rework processes, and limited flexibility.

The new solution developed jointly by Fraunhofer FEP and five other institutions addresses the issues mentioned above. The process principle is illustrated in the diagram below: First, a coating is applied onto a substrate film. Next, nanolithography imprinting (NIP) technology is used to transfer the pattern from the mold onto the coating. Finally, the coating is cross-linked and cured via electron-beam irradiation, resulting in the finished decorative film. This decorative film can be adhered to the surfaces of conventional photovoltaic modules or metal components, instantly transforming their appearance.

Schematic diagram of the nanoscale imprinting pattern transfer technology using electron-beam crosslinking; Source/Figure: Fraunhofer FEP By using customized nanoimprint molds, it’s possible to achieve diverse aesthetic design solutions while decoupling the process from photovoltaic module production. This approach enables architectural PV projects to leverage mass-produced mainstream PV modules while still meeting the unique design requirements of building aesthetics. The project team at Fraunhofer FEP has already established a pilot production line employing the aforementioned nanoimprint technology, successfully achieving roll-to-roll production of decorative films with a width of up to 1200 mm. Note that the film substrate is made of ethylene-tetrafluoroethylene (ETFE), a material known for its extremely low surface energy and poor adhesion to other materials. To address this challenge, the project team implemented a plasma treatment method to significantly enhance the substrate's surface adhesion properties. The appearance and conversion efficiency of the PV modules coated with these films were subsequently tested at the Institute for Solar Energy Research Hamelin (ISFH).