German researchers have unveiled a special self-healing coating that could fix microscopic cracks in solar glass by reducing its weight by 40 percent and making it seven times stronger.
The technology was created by Gräfelfing-based solar energy company EXXERGY and its subsidiary EXXOSQEL. For the effort, the firm teamed up with Würzburg’s Fraunhofer Institute for Silicate Research ISC.
The innovation could additionally make solar panels 30 percent lighter. According to the team, lab tests have already shown promising results. The coating increased the strength of 0.08 inches (two-millimeter) glass samples by up to four times. Simultaneously, thinner 0.04 inches (one-millimeter) samples became up to seven times stronger in contrast to untreated, non-tempered glass.
Efforts are underway to adapt the coating for full-sized solar panels. “The steps from a laboratory sample to a large solar module require considerable expertise in scaling up material synthesis, application technology, and module manufacturing,” Thomas Sauer, EXXOSQEL managing director, said.
Fixing tiny solar glass cracks
Glass is a critical component of solar panels, as it protects solar cells and other electrical parts from weather conditions and lets sunlight pass through. It accounts for up to 80 percent of a solar panel’s total weight.
Conventional solar panels typically weigh between 2.3 and 2.7 lbs per square foot (11 and 13 kilograms per square meter). Heavier designs can, however, reach 3.3 lbs per square foot (16 kilograms per square meter). Using thinner glass could reduce solar panel weight, but increase the risk of damage.
Producers usually strengthen glass through heat treatment, which makes it harder for cracks to spread. However, conventional thermal tempering becomes difficult when glass thickness drops to 0.08 inches (two millimeters) or less.
Credit: EXXOSQEL
The German team’s new coating addresses this issue by creating chemical bonds inside the cracks. According to EXXOSQEL, its material forms a three-dimensional (3D) composite structure that creates covalent bridges at the molecular level.
“Specifically, we create a three-dimensionally cross-linked composite from several components, whose matrix forms covalent bridges in the microcracks at the molecular level after the coating is applied,” Sauer added.
These bonds raise the energy required to break the glass, making thinner sheets considerably stronger. EXXOSQEL estimated that reducing the glass mass by 40 percent could lower the overall weight of certain solar panels by 30 percent.
From lab to market
The team now aims to make the coating suitable for mass production. Fraunhofer ISC is helping produce the coating in batches of up to 100 liters (26.4 gallons). The institute is also working to automate the coating process so manufacturers can integrate it into existing production lines.
At the same time, EXXERGY is collaborating with the Fraunhofer Center for Silicon Photovoltaics CSP to test the coating on larger glass sheets and solar modules. As per EXXOSQEL, the development is nearing Technology Readiness Level 6 (TRL 6), which indicates that a model or a prototype has already been demonstrated in a relevant environment.
Sauer explained why this advancement matters. “This means that we have already successfully produced initial prototypes in standard dimensions under conditions close to real-world applications, and stress tests are currently underway,” he said in a press release.
Their next goal is to reach Technology Readiness Level 7. This category involves demonstrating the technology in an actual operating environment. If successful, the coating could reduce the amount of raw materials and energy needed for manufacturing solar panels.
EXXOSQEL will showcase a demonstration of the technology at Glasstec 2026 in Düsseldorf. The event is the world’s leading international trade fair for the glass industry. It will take place from 20 to 23 October.