Probing light-harvesting mechanisms in natural and artificial systems with atomic precision

• Applicant: Dr. Anna Roslawska
• Subject Area: Experimental Condensed Matter Physics ; Physical Chemistry of Solids and Surfaces, Material Characterisation ; Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 534367924

The interaction between light and matter is essential for many mechanisms of life and technology. Important examples are photosynthesis, luminescence, and energy harvesting. They rely on efficient absorption/emission and transport of excitation within the system, as in photosynthesis, where many energy transfer steps separate photon absorption and chemical reaction. While the fundamental processes governing this energy conversion process are sufficiently described, many details of these mechanisms still need to be clarified. That includes the role of molecular vibrations, coherence and involved excited states. One of the challenges related to probing these mechanisms is that the parameters arising at the scale of an individual unit (< 1 nm) influence the interaction strengths between single pigments, thus, the final energy conversion efficiency of the whole process. These details are obscured when probed by the usual ensemble averaging methods. Understanding the role of the local atomic-scale environment of each pigment on the absorption efficiency and energy transfer will enable improving the design of molecules and structures that optimally absorb photons and transport the collected energy. This project aims to address this challenge by studying light-matter interactions at atomic resolution in biologically relevant and artificial molecular systems. We will use molecules decisive for photosynthesis, such as chlorophyll and carotene, to assemble nanostructures capable of absorbing single photons and to study the propagating excitation that can eventually be converted into single charges. Thanks to this approach, we will be able to probe key steps of light collection in natural systems for the first time with atomic precision. Furthermore, we will focus on the influence of structural arrangement, the presence of different molecular species, single charges, molecular vibrations, coupling with the local environment, and the role of coherence in light-driven processes. Based on these advances, we will develop efficient artificial light-gathering structures with atomic precision. Understanding these mechanisms at the atomic level is crucial to efficiently collect and guide excitation in any system, especially in artificial organic materials that collect light.

• DFG Programme: Independent Junior Research Groups
• Major Instrumentation: Optical spectrometer
• Instrumentation Group: 1800 Spektralphotometer (UV, VIS), Spektrographen (außer Monochromatoren 565)