Research
Our group explores the nature and dynamics of excitations in materials for energy-related applications. Examples of these are photonic materials for light emission, magnetic materials for information storage or mixed electronic-ionic materials for energy storage. We study these materials with advanced time-resolved ultrafast spectroscopies on timescales as short as femtoseconds, using light pulses with energies from the X-ray to the infrared region. With this approach, we discover novel concepts and mechanisms for energy applications in emerging functional materials, for example hybrid perovskites, low-dimensional 2D materials, or molecular semiconductors. We work together as an interdisciplinary team of chemists, physicists and material scientists to achieve these goals.
For a record of our publications, please see our Google Scholar profile.
Employing our expertise in physical-chemistry and materials science, and driven by the motivation to make fundamental material discoveries, we work on the following themes.
Ultrafast Dynamics of Emerging Semiconductors
Excited states are formed when light interacts with semiconductor materials. The electronic nature of these excited states, such as the energy levels, angular momentum or interactions, are of key importance for their performance in applications. The dynamics of electronic states occur on ultrafast timescales and involve interactions with the underlying material structure, conversion between different excited states, or transfer between materials in heterostructures.
We are investigating how these dynamics are controlled by structure and composition of semiconductor materials. We are particularly interested in material systems with complex or spatially-disordered energy landscapes, the ultrafast structural responses of materials to electronic excitations and charge localization in novel semiconductors to maximize control of luminescent recombination.
Science 2016, 351 (6280), 1430–1433.
Nature Materials 2021, 20 (5), 618–623.
Nature Photonics 2020, 14 (2), 123–128.
Chiral Hybrid Semiconductors
A recent material focus of our research are the hybrid perovskites, which represent an unexpectedly exciting class of semiconductors with a range of surprising optoelectronic characteristics. We fabricate these materials using solution-based self-assembly, which creates opportunities for tailoring functionality for optoelectronic applications. We have made key discoveries on the physical origins of the exceptional properties of these materials, e.g. their high luminescence yields. Recently, we are investigating hybrid metal-halide systems with chiral crystal structures and chiroptical activity for photonic applications.
Science Adv., 2023, 9 (35)
J. Am. Chem. Soc. 2022, 144 (31), 14079–14089.
Adv. Opt. Mater. 2022, 10 (14), 2200204.
Magnetic Semiconductors for Optical Angular Momentum Control
Ultrafast optical read-out and writing of orbital and spin angular momentum states holds potential for next generation information storage. For this, magnetic semiconductors offer exciting opportunities for exploring fundamental aspects of the interactions between excitations and angular momentum towards optical spin-control concepts in applications. We are currently exploring the opportunities arising from the versatile metal-halide perovskite material platform to achieve breakthroughs in magnetic hybrid semiconductors, as well as ultrafast dynamics of emerging solution-processable low-dimensional magnetic nanomaterials.
ACS Nano 2023, 17 (11), 10423–10430.
Nat. Commun. 2022, 13 (1), 3320.
Nat. Commun. 2021, 12 (1), 3489.
Nano Lett. 2020, 20 (8), 5678–5685.
Dynamics of Electronic-Ionic Materials
The dynamics of electronic-ionic transport and the mechanisms of charge-ion conversion are fundamental steps in battery materials and electrochemical devices. We are using optical spectroscopy to investigate these processes on local and fast timescales in emerging materials for energy storage. A recent interest is the optical control of ionic transport, fundamentals steps of charge-to-ion conversion, and how the presence of charge populations affects local ionics. Under this theme we are participating in the GRK 2948 on Mixed Ionic-Electronic Transport.
Energy Environ. Sci. 2022, 15 (10), 4323–4337.
Nano Lett. 2020, 20 (8), 5967–5974.
Advanced Ultrafast Spectroscopy
Cross-cutting our research themes is the development and application of novel ultrafast spectroscopies for characterization of functional materials. Our advanced methods range from beamline-based time-resolved X-ray scattering to near-field approaches in high-resolution optical spectroscopy, which we employ to resolve elementary steps in functional materials across a wide range of length, time, and energy scales. A recent interest is the local mapping of spin dynamics and ionic transport.