Easy retrofit of facades and ultra-thin glass solar panels

Cleaning glass facades and installing solar is expensive and time consuming. Dirt reduces the productivity of solar modules. However, the Fraunhofer Institute for Organic, Beam Electron and Plasma Electronic Technologies (FEP) has now succeeded in applying crystalline titanium oxide to ultrathin glasses using a roll-to-roll process, thus obtaining Hydrophobic surfaces become super hydrophilic under UV light.

Initial results of this showcase of some NewSkin open access The upgraded facilities will be showcased at the Fraunhofer joint stand, number C2-528, in BAU 2023, April 17–22, in Munich, Germany.

In 2021, photovoltaic will account for 8.9% of total electricity consumption in Germany with a generating capacity of 50 TWh. This percentage must increase to achieve a sustainable energy transition. The stain-resistant, easy-to-clean surface ensures transparency and cleanliness of the façade, and more efficient and consistent energy production for solar, with lower maintenance costs.

“We are focusing on photochemical hydrophilicity on the surfaces here,” explains doctoral student Valentin Heiser from FEP. “To enhance this effect, we first applied crystalline titanium oxide to ultra-thin glass by a rolling process. This is very effective. The ultra-thin and light glass can then be applied to facades or directly integrated into solar modules as a mixed ingredients—and even on curved surfaces.”

Titanium dioxide changes its hydrophilicity, that is, its resistance to water, when exposed to UV radiation (e.g., activated by sunlight). Without irradiation, it is hydrophobic, meaning it forms water droplets. After irradiation, it is super absorbent, or completely moistened. In the photophilic hydrophilic case, the surface changes from hydrophobic to superhydrophilic after about 30 min of UV irradiation like the sun.

On the surface with this titanium dioxide coating, no or only very little dirt can be deposited. For example, if traffic dust, sand or other dirt is deposited on a glass or solar panel facade, it will be washed away by the nightly hydrophobicity of the surface through granulated raindrops. Additionally, the cyclical alternation of hydrophobic and super-absorbent properties means dirt doesn’t stick to surfaces during the day.

UV activated titanium oxide also decomposes organic molecules on the surface by photocatalysis. This creates antimicrobial and sterile surfaces of particular interest in Medical engineering or related to flexible display.

Researchers at Fraunhofer FEP have now developed the first coatings: Specifically, a thin roll of glass 30 cm wide and 20 m long, with a glass thickness of 100 micrometers, is coated with a 30––thick layer of titanium oxide. 150 nanometers in a roll. -to-roll the system. This pilot plant for the roll coating of thin glass (VON ARDENNE FOSA LabX 330 Glass) is located at Fraunhofer FEP.

One challenge for this showcase project was that thin glass is a very new substrate with important processing requirements, as it is fragile and reacts sensitively to thermal and mechanical stresses. Second, titanium dioxide acquires hydrophobic and hydrophilic properties only when it is in crystalline form. For this, it requires high temperature during production. Up to now, sputter coatings with these requirements could not be implemented in roll-to-roll technology because conventional substrates, such as film, cannot withstand high temperatures. This is where thin glass provides an alternative.

Thanks to this work through NewSkin, Fraunhofer FEP scientists are now working on combining the properties of titanium dioxide and thin glass cup optimal and cost-effective way to bring innovative products to market with the industry. Researchers from Uppsala University, a NewSkin partner, are working on transferring the results even to polymer membranes.

In the future, Fraunhofer FEP’s work will also be carried out on layer systems that can be activated not only by UV light but also by visible light. For example, the production and embedding of nanoparticles or doping with nitrogen are also being considered.

Provided by the Fraunhofer Institute for Organic Electron Technology, Electron Rays and Plasma