BESSY upgrade
Two forward-looking projects at the Helmholtz-Zentrum Berlin (HZB)
Variable light pulses and better use of sunlight – these are the two future projects at the Helmholtz-Zentrum Berlin for Materials and Energy, which will make the research radiation source BESSY unique.
Making the photon source BESSY II more brilliant and sharp and cells more powerful with novel materials. These are the aims of two ambitious projects of the Helmholtz-Zentrum Berlin for Materials and Energy in Adlershof. “With these two forward-looking projects, we are creating worldwide unique structures,” says Prof. Bernd Rech, provisional scientific director of the HZB since May 2017. The physicist started off at the HZB as head of the Institute Silicon Photovoltaics in 2006. He is also professor at the faculty for electrical engineering and computer science of Technical University Berlin.
The synchrotron radiation source BESSY II provides soft X-ray pulses with a fixed length of ca. 17 picoseconds (one trillionth of a second) and high photon flux. For just a few days every year, the pulses are switched to a duration of two picoseconds, which requires decreasing the stored energy and thus photon flux. This is due to improve with the new concept called BESSY VSR (variable-pulse-length storage ring). Researchers conducting experiments on any of the available 47 measurement stations may choose between short or long light pulses without loss of intensity.
“Such a storage ring does not exist anywhere in the world, says Rech. It will close the gap between synchrotron radiation sources and free electron lasers. Although the latter can conduct measurements using even shorter light pulses, they are unable to cover such a broad spectrum of analyses, including energy and materials research, life sciences, catalysis and photosynthesis.
One of the HZB’s key areas is analytics of the thin-film materials used in solar cells. Ultra-short light pulses enable researchers to shed light on geometric and electrical structures of materials as well as ultra-fast processes, such as magnetic and optical switch operations on interfaces. Their research results will contribute to making components in energy conversion and storage more efficient and cost-effective. The current standard are solar cells made from silicon, which have a maximum degree of efficiency of 20%. HZB researchers now set their hopes on materials with Perovskite crystal structures. “Perovskite solar cells are among the most promising types of materials,” says Rech. Combining layers that contain silicon as well as perovskite into a tandem cell promises better use of sunlight. “This would make degrees of efficiency of over 30% possible,” explains the physicist.
The HZB is cooperating with universities in Berlin and Potsdam as well as with partners from the private sector to further explore perovskites. The HZB will create additional laboratories and three teams of young and internationally renowned scientists. One of their key interests is to find out how the polycrystalline material can be produced on a large scale using conventional printing technology. Another is to see whether the low concentration of lead found in solar cells is potentially harmful. Could the heavy metal be replaced? How can the life span of the intriguing future solar cell material be increased to, say, 25 years? What happens on the interface between silicon and perovskite? These are but some of the questions asked at the HySPRINT (Hybrid Silicon Perovskite Research, Integration & Novel Technologies) lab, which was founded in January 2017 as one of seven Helmholtz Innovation Labs in Germany.
by Paul Janositz
Link: www.helmholtz-berlin.de/index_en.html