Summer in the laboratory: 24 students from all over the world start their summer project
Group picture at arrival day at HZB. © S. Kodalle/HZB
For eight weeks the summer students are now working on a research project at the Helmholtz Centre Berlin. Experienced scientists of the HZB will support them. On Thursday, 30 August, they will present their results.
This year, 282 young people from all over the world applied to take part in the HZB's summer program. But only 24 places are available. Now the selected students can start their project. They come from 14 different countries, including Egypt, China, Cuba, Russia and Thailand, and study STEM subjects in Bachelor's or Master's programmes at their home universities. For many, the summer student program is the first step into research.
"Once again this year, many HZB researchers have signed up with project ideas for summer students and agreed to intensively support the students," says Gabriele Lampert, who coordinates the summer student program. "I know that this also means additional work, but the experience from recent years also shows that it is often worth it for both sides. Because it happens again and again that summer students come back later, for example for a doctorate, as cooperation partners or users.
Finally, the summer students will present their results on 30 August 2019 at 11:00. Three students will give a short lecture, all others will explain their project with a self-designed poster.
- Magnetic imaging: Micro-flowers increase the local magnetic fieldMaterials with magnetic nanostructures have many potential applications such as in spintronics. To explore such materials, nanoscale magnetic-sensitive imaging techniques are very useful, but up to now only weak magnetic fields could be applied during the imaging process. Now an international collaboration led by Dr. Sergio Valencia, HZB, has developed an approach that overcomes this limitation. The team designed tiny magnetic flux concentrators (MFCs), into which the sample is placed. The geometry of the MFCs resembles a flower with a number of petals which focus the applied magnetic field into its center. This greatly expands the magnetic field range available during imaging, and so the range of magnetic systems that can be investigated. The micro-flowers, enhancing magnetic fields locally, can find application in different nanometric magnetic microscopy techniques.
- CIGS-perovskite tandem cell achieves record efficiency of 25.5 %A Berlin-based team from HZB and Center for the Science of Materials Berlin (CSMB) at the Humboldt-Universität zu Berlin has set a new record for a tandem solar cell. Using a combination of a CIGS semiconductor layer and perovskite, along with several optimised intermediate layers, they were able to convert 25.5% of sunlight into electrical energy. The previous record for this combination of materials and this size of cell stood at 24.6%. The new record has been certified and is visible in the prestigious Solar Cell Efficiency Tables (the "Green Tables"), which serve as the definitive ledger for the global photovoltaic community.
- Disorder creates new properties in compound semiconductorsAn international research team has demonstrated that the intrinsic disorder of the compound semiconductor CuInSnS₄ can be exploited to influence its optical properties. While the atomic vibrations also sense the local disorder, their response is averaged over many different local environments and therefore appear isotropic, as expected for a cubic crystal. In contrast, the optical excitations, known as excitons, are much more sensitive to the local arrangement of atoms. Surprisingly, they show a direction-dependent optical response even though the average crystal structure is cubic. These findings shed new light on the relationship between disorder and material properties, opening up new options for targeted 'disorder engineering' in optoelectronic and photocatalytic devices.