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Home » Fraunhofer, the PhotonFlex project: An USHIO excimer story

Fraunhofer, the PhotonFlex project: An USHIO excimer story

Fraunhofer – today’s development for tomorrow’s excimer future

Fraunhofer is Europe’s largest application-oriented research organisation. This community wants to bring research from the laboratory to the benefit of the industry. That also includes implementing solution concepts for public projects, funded by the state and executed by field professionals. These industry experts include M. Sc. Ludwig Pongratz, Project Manager for Micro and Nano Structuring at the Fraunhofer-Institute for Laser Technology, who’s been working on the PhotonFlex project. This project consists of creating a roll-to-roll printing system of organic solar cells, such as flexible solar cells on plastic films. Pliable and transparent, these solar cells have the potential to fuel further energy production on an industrial scale. Charge anywhere, anytime. An ambitious, yet attainable goal, thanks to Ushio.

We could not have achieved these results without the Ushio excimer technology. It was the missing compact piece to our puzzle. The Ushio team has been dedicated to this project from start to finish, their expertise and service has only intensified the outstanding results the excimer technology generated for the project. Excimer fixed our surface adhesion to achieve outstanding flexibility and transparency the PhotonFlex project required. Ushio made it happen in the best possible time, size and way.”
– M. Sc. Ludwig Pongratz
Project Manager at Micro and Nano Structuring,
Fraunhofer-Institute for Laser Technology

For the PhotonFlex project, Fraunhofer committed to scaling a laboratory success to large-scale production. During the process, Pongratz encountered a particular challenge – levelling out the surface energy from the electrically conductive layer and onto the transparent plastic wrapped around the roll. The thin layers must be applied precisely onto the ITO foils, and it must be completely homogeneous to ensure an equal energy state over the entire width of the roll. If not, the consistent quality of the organic solar cells could be compromised. A vital feature and the solution securing this had to fit within a 20x20x30cm frame. Pongratz scoured the market for a solution fit for the job.

Ushio excimer – concise inline perfection

Pongratz knew excimer technology was the way to go. Excimer irradiation is created by using a specially coated, noble gas filled VUV 172nm lamp that emits high-energy photons. This type of irradiation is particularly useful in a multitude of applications that require surface energy enhancement or a selective surface modification. In this particular case, the enhanced surface energy secures a stronger adhesion of the material onto the surface, drastically improving product quality.

Excimer technology would enable Fraunhofer to produce the solar cells with active absorbers from the liquid phase using laser-based techniques for cell switching and highly efficient drying. But could this solution fit the compact space available? Excimer technology eliminates the need for a vacuum chamber, as it’s a fully inline process. The Ushio excimer module measures only 15x15x15cm so it fitted the roll-to-roll system perfectly.

Fraunhofer & Ushio – more than just the perfect fit

Shaping the future is not an easy task – it takes a lot of people, brands and technologies to cooperate in finding an operative and constructive solution. Pongratz comments on the process: “The Ushio team was very responsive and eager to try this new application of their module. They sent over a demo model for us to use and test. All it took was one day of training to find out how we could use the excimer technology to our advantage. As it turns out it was the missing key to our roll-to-roll solar cell production. The surface adhesion excimer delivers, and the services provided by the Ushio team, are so outstanding we’re even applying it in our next project that kicks off in the summer of 2019. When it’s that good, there is no doubt.”

The PhotonFlex project has been a complete success. The implementation of the Ushio excimer technology enabled the Fraunhofer team to find a scalable production method for organic solar cells. Pongratz and his team are dedicated to further supporting the research and mechanical engineering sectors in North Rhine-Westphalia, thereby boosting the region’s solar industry as a pillar of sustainable resource utilisation. In their next project, they will also rely on Ushio excimer technology for reliability, stability and efficiency.

The PhotonFlex project is run by the Fraunhofer Institute for Laser Technology (ILT), together with the Chair of Laser Application Technology (LAT) at the Ruhr University Bochum, LIMO GmbH, Coatema Coating Machinery GmbH, Ortmann Digitaltechnik GmbH and Ushio Europe B.V.

PhotonFlex is funded by the European Regional Development Fund (ERDF) under the funding label: EU-1-1-078E/EFRE-0800066


The Fraunhofer-Institute needed an inline surface curing technology that would fit into a very compact space.


Ushio excimer module – cured the surface layer energy level to perfection AND made the perfect compact fit in the limited roll-to-roll production module.

Why excimer tech?

  • compact
  • flexible
  • efficient

Why Ushio?

  • engaged
  • uncomplicated
  • result-driven

Project run:

Summer 2016 – Summer 2019

Tech perfection time:

  • 9 months of testing, experimenting, fine-tuning of settings.
  • One day of training in the excimer technology.
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