Fraunhofer ISE and the University of Freiburg developed semi-transparent organic PV modules using industrially scalable processes
The 210.25 cm² modules achieve up to 9.26% efficiency and 43.2% average visible-light transmittance
Flexible module prototypes retained their original efficiency after 1,274 bending cycles
Researchers at Germany’s Fraunhofer Institute for Solar Energy Systems ISE (Fraunhofer ISE) and the University of Freiburg have developed semi-transparent organic photovoltaic modules using industrially established manufacturing processes. The modules are intended for applications requiring both power generation and light transmission, including building façades, greenhouses, and vehicle roofs.
Scaling organic PV from small laboratory cells to larger modules remains challenging, as laboratory manufacturing methods cannot always be transferred to industrial production. To address this challenge, the researchers produced the modules using sputtering and slot-die coating, both established manufacturing processes that can be scaled to larger areas.
According to Fraunhofer ISE, the researchers applied all the solar-cell layers suitable for coating using the slot-die process, with virtually no performance loss. The back electrode was deposited separately through sputtering, another established industrial process.
The resulting semi-transparent modules measure 14.5 cm × 14.5 cm and cover an area of 210.25 cm². They achieve efficiencies of up to 9.26%, with a visible-light transmittance of 43.2%. This combination corresponds to a light utilization efficiency (LUE) of up to 4.0%, a metric that accounts for both power-conversion efficiency and light transmission.
More than 100 solar cells are interconnected within each module using laser structuring. The module architecture comprises a back electrode designed to redirect near-infrared light into the absorber, an organic semiconductor absorber layer, and a transparent, metal-free top electrode made from the conductive polymer PEDOT:PSS. The absorber and top-electrode layers are applied using slot-die coating. Project partner Heraeus Epurio developed the PEDOT: PSS formulation to improve module transparency.
Fraunhofer ISE says further optimization could raise light transmittance without reducing efficiency. Organic modules with transmittance exceeding 50% could replace window glass in façades and greenhouses. Lower-transparency versions could suit applications where tinted glass is preferred, such as vehicle roofs and façade elements.
Since slot-die coating is compatible with roll-to-roll manufacturing, the process can also be used to produce organic PV modules on film. Under the project, the researchers produced flexible module prototypes that retained 100% of their initial efficiency after 1,274 bending cycles around a rod with a diameter of 15 mm. Project partner ROWO Coating manufactured the films, while the next development stage will focus on increasing the flexible module area.
The research paper titled “Toward Scalable Semitransparent Organic Photovoltaics: Slot-Die-Coated 210-cm² Modules With Visible Transmission of Up to 50% and LUE Up to 4%” is published in Joule.
Recently, Fraunhofer ISE and Source Energy developed silicon solar modules for satellite applications using M10 Solar Equipment’s shingle-matrix interconnection technology. The modules are designed as a lower-cost alternative to the III-V technology commonly used in space (see Fraunhofer ISE & Source Energy Develop Silicon Solar Modules For Space).
