Fraunhofer Institute for Microstructure of Materials and Systems IMWSEXXOSQEL GmbH and the Fraunhofer Center for Silicon Photovoltaics CSP have jointly developed a glass-glass PV module with front and back glass panels each only 1 mm thick. A reactive coating compensates for the lower mechanical strength and stiffness of the ultra-thin glass. The demonstrator highlights the potential for lighter, more material-efficient solar modules for use in building-integrated photovoltaics and further applications.
Thinner glass is an obvious approach in the photovoltaic industry for reducing material consumption, module weight, and thus transportation and handling costs. However, it typically offers less mechanical strength and in addition, it flexes substantially more. Especially in the event of hail and other extreme weather events, the protective function of the front glass for the underlying module components must be maintained. Solutions that combine thinner glass with high robustness are therefore in demand.
To this end, Fraunhofer CSP and EXXOSQEL have developed a prototype glass-glass module with 1-mm-thick front and back glass in a 300 × 200 mm format. The module uses established encapsulation materials and series-connected quarter-cells made from bifacial M6-9 busbar PERC cells; each quarter-cell delivers approximately 1.58 W.
At the heart of the development is EXXOSQEL’s multi-component, reactive surface treatment that is applied directly to the glass. It reacts with hydroxyl groups on the glass surface that is characterized by microcracks induced during the cooling and hot forming process; the coating forms covalent bonds with the glass matrix bridging the gaps in the microcracks and thereby strengthening the surface. Its optical properties are tailored to the glass to minimize losses in the transmission resulting in nearly no noticeable efficiency losses.
Building the prototype required customized manufacturing conditions: The ultra-thin glass had to be reliably integrated into the lamination process. “The module was manufactured using a standard PV laminator; process parameters such as temperature, pressure, and equipment configuration were adjusted,” says project manager Ringo Köpge of Fraunhofer CSP. The current prototype is a demonstrator roughly the size of a DIN A4 sheet. Further tests are needed to confirm whether the targeted robustness holds up in large-format modules under hail impact.
For the implementation, Fraunhofer CSP contributed its expertise in PV module integration: the selection and interconnection of cells, the use of suitable encapsulation materials, and the adaptation of lamination parameters to the thin glass. This allowed the coating to be tested in the module assembly rather than exclusively on glass samples. “The special coating process is not limited to the demonstrator module but can also be applied to standard solar modules,” emphasizes Köpge.
In laboratory tests, the strength of 2-mm glass increased from 79 to up to 558 MPa; for 1-mm glass, it rose from 184 to up to 1,348 MPa. These values refer to glass samples and do not yet constitute proof of the field durability of large-format PV modules. “Compared to the conventional approach of achieving strength primarily through greater glass thicknesses, this approach offers significant advantages. The potential weight savings amount to up to 40 percent; energy consumption and CO₂ emissions associated with material procurement could also decrease,” says Thomas C. Sauer, CEO of EXXOSQEL. “The coating can be integrated into existing glass manufacturing or finishing processes.”
The next steps in development include applying the technology to large-format modules and testing hail resistance. The project team sees particular potential for lightweight module designs, printed front glass panels, and building-integrated photovoltaics.
(August 12, 2026)