PhD student of HZB earns Best Presentation Award of the Young Crystallographers
Frederike Lehmann earned an award for her presentation at the annual meeting of the German Society for Crystallography. © privat
Frederike Lehmann received a prize for her presentation at the annual conference of the German Society of Crystallography in Leipzig on 28 March 2019. She is doing her doctorate in the Department of Structure and Dynamics of Energy Materials at the HZB under Prof. Dr. Susan Schorr at the Graduate School HyPerCell.
In her lecture she presented her work on hybrid perovskite materials, which are being investigated as an exciting new class of materials for highly efficient solar cells. Hybrid perovskites are semiconductors and have a so-called bandgap in the appropriate energy range, so that the energy-rich blue and green parts of the solar spectrum in particular can be efficiently converted into electricity.
Frederike Lehmann's work deals with the chemical synthesis of hybrid perovskites and the analysis of their properties. She investigates both inorganic (CsPbI3) and organic perovskites in which organic molecules such as formamidinium or methylammonium are incorporated into the structure instead of cesium. By targeted substitution, she succeeded in producing a high-temperature modification at room temperature whose band gap is particularly suitable for solar cells. This is particularly important because perovskites are used in thin-film solar cells whose quality suffers in high-temperature processes. The "Best Presentation Award of the Young Crystallographers" is associated with a book voucher.
- 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.
- Perovskite solar cells: Predictions of long-term stabilityReliable statements about the long-term stability of perovskite solar cells are still difficult to make. However, a new study by Dr Carolin Ulbrich’s team, published in the renowned journal Joule, highlights which methods are useful for this purpose and identifies areas where further research is needed.