Öffnet in neuem Fenster Opens in a new window Öffnet externe Seite Opens an external site Öffnet externe Seite in neuem Fenster Opens an external site in a new window

Innovation Lab HySPRINT

Using solar energy against the global warming


The physicist Klaus Jäger aims for the improvement of solar cells by using optical nanostructures. He does not only utilize standardized solar spectra, but also wants to include real weather data. Science determines his life - and led him to become an uncompromising fighter for climate protection.

Klaus 3

For several months, young people from the movement "Fridays for Future" have been demonstrating worldwide for a better climate protection. During their school strike, they have been holding the posters high up in the air with the sentences like: "There is no planet B" or "We are not studying for a destroyed future".
Together with thousands of scientists HZB researcher Klaus Jäger supports the concern of young people under the name "Scientists for Future". He was also at one of their protests in Berlin. "For a long time, I had the feeling that nothing is happening in the public debate," the physicist says. "But now it is getting a boost." Jäger is interested in social responsibility and actively participates in the discourse – therefore, he took part this year in the re:publica Berlin - internet and digital society conference.

Klaus Jäger usually spends his daytime at the office in Adlershof. A plastic apple moves up and down on his windowsill driven by solar cells. "I am very glad that the climate movement is finally gaining momentum," Jäger says while gesturing decisively. "These are topics that we have been working on for decades, knowing they are important. In the end, climate protection is protection of humankind." Klaus Jäger dedicated himself to solar energy research. Since 2015, he has been working at the Helmholtz-Zentrum Berlin in the junior research group "Nano-SIPPE" led by Christiane Becker –meanwhile as a deputy group leader. She is focused on the experimental work, he - on theoretical. "In particular, we simulate nanostructures for solar cells," the 36-year-old scientist explains. "Our goal is to identify routes for improving solar cells with optical nanostructures. Currently we work mainly with perovskite/silicon tandem solar cells." Jäger's research is carried out in close collaboration with the Zuse Institute Berlin (ZIB). He is director of the “Berlin Joint Lab for Optical Simulations for Energy Research" (BerOSE), in which the HZB, ZIB and Freie Universität Berlin are cooperating. He spends around two days per week at ZIB in Dahlem and the rest of the time he is in Adlershof.

Jäger was born in Austria, he grew up in the mountain region Wilder Kaiser in the Tyrol. "Where ZDF (German TV) produces the TV series ’Bergdoktor,’" he adds. He points to his desk calendar full of idyllic landscape shots. He likes to travel there. He visits Tyrol several times a year for hiking and skiing.
After completing his high school exams in Austria, Jäger studied physics at ETH Zurich. Next, he went to the Dutch city of Delft for doing a PhD on optical models for solar cells. After a short experience in industry - he was employed by a company working on flexible solar modules – Jäger became a postdoc in Delft. He compiled a textbook on solar energy and eventually came to the HZB in Berlin.

Today, Jäger is also active in the HEIBRiDS graduate school ("Helmholtz Einstein International Research School on Data Science"), in which the Helmholtz Association, the Einstein Center Digital Future and Berlin universities work together. "We have a very exciting project with our PhD student Peter Tillmann. We want to combine our high-precision optical simulations for solar cells with real weather data."
The background of the project is that in solar cell simulations mostly standardized solar spectra are used. However, both the total irradiation of sunlight and the position of the sun vary depending on time and place. "The important questions are: How good are tandem solar cells under real sunlight? Are they in the field as good as under idealized conditions? Would it make sense to design the solar cells differently, depending on the location?" Jäger lists these questions – and he strives to answer them soon. "I think we could provide architects a more precise planning tool for photovoltaic systems.

Jäger is someone who also sees his responsibility as a scientist also in engaging in the public debate. If you ask him about his hobbies, Jäger answers: "I am interested in politics. That's my hobby." He tweets a lot under the name "@the_solartube", amongst other things when it comes to climate protection. Jäger regularly visits the Berlin Museum of Natural History on Friday afternoons, where young people can talk to scientists after the "Fridays for Future" protests. "For me teaching is just as important as research," says Jäger.
He was amazed how well the young people are informed. "The level of information is often higher than that of adults." Do some questions recur repeatedly? Jäger thinks something over. "There's always the question how to store energy independently of day time and season," he says. That is, indeed, a great problem. "But I'm confident that we will find a solution - if the will is there." Making the world a better place, he is also concerned about diversity at the workplace - especially regarding lesbians, gays, bisexual and transgender people. He decided to deal openly with his homosexuality, even though it is not yet taken for granted in science, says the physicist. He is also involved in the Berlin LGBT network "Unicorns in Tech," where he has already given lectures on solar energy.

Does Jäger believe that climate change can still be stopped? As an answer, he shows a cover of the magazine "National Geographic". It depicts an apocalyptic scene from a Canadian refinery. "Guess from when is this front page?" asks Jäger finally replying himself: "From 1981." Already back then, society discussed the climate change and the global warming by two degrees Celsius. Nonetheless, he is optimistic. So far, good novel technologies often lead to disruptive change. For example, cars replaced horse carriages and digital cameras superseded analog cameras. This could also be the case regarding climate change. "We are late, but not too late."

Text in German: Anja Mia Neumann
Translation: Mariia A