The KahmannLab stands on three broad legs, which are our fields of expertise. Synthesis of (solution-processed) novel materials and their development/optimisation goes hand in hand with in-depth photophysical characterisation and a special attention to local information enabled through optical microscopy. We love light-matter interactions and everything that emits or absorbs light.
Ultimately, the expertise on materials and photophysics works in concert to design, characterise, and to improve the performance of optoelectronic devices. Boosting our capabilities by means of computational approaches is a further central concern of our strategic work.
As such, we work on the boundaries of classical disciplines, such as physics, chemistry, materials science, and electrical engineering. Benefitting from diverse scientific backgrounds and experimental skill sets is at the heart of the KahmannLab’s philosophy.
What happens when materials absorb light? How fast do they emit light and at what energy? How is this affected by processing conditions? And what can we learn from looking at these aspects under the microscope?
Photoluminescence spectroscopy and microscopy in all their facets are our dearest experimental techniques. We study the interaction of light with matter to discover new properties or to understand exciting phenomena encountered in new compounds.
We particularly care about dynamic processes, such as recombination and diffusion of excitations, as well as the spatial correlation of different signals. Developing computational approaches for smarter analysis are an important concern to treat these large data sets.
We love semiconductors & in particular those processed from solution. Our work considers organics compounds, (e.g. conjugated polymers & small molecules), inorganic compounds, (colliodal nanocrystals), or hybrid compounds (halide perovskites).
Intricate structure-property relationships and how they can be tailored, for example, through interaction of organic and inorganic building blocks, is a key objective of our work. Emission of polarised light or anisotropic transport of charge carriers are two examples of important properties that can be tuned in such a way.
At the moment, we are particularly interested in the class of low-dimensional halide perovskites, whose electronic dimensionality can be manipulated through the intelligent choice of spacer molecules.
Impressions from the Lab
The wide environement of the Institute of Physics provides a multitude of relevant characterisation techniques, e.g. X-ray diffraction, electron microscopy, circular dichroism spectroscopy, and Raman spectr-microscopy.
The Chameleon is a powerful broadly tuneable (660-1320 nm) laser source that emits pulses of around 100 fs duration at 80 MHz repetition rate and up to 4 W. We use a pulseSelect pulse picker from APE to reduce the repetition rate (down to 310 Hz) and a HarmoniXX second harmonic generator to cover wavelengths down to 330 nm.
The heart of our microscopy lab is a manual IX73 inverted microscope from Evident. Beam shaping enables us to use the platform both for focused and for wide-field microscopy using LEDs and the femtosecond laser. The system is directly coupled to our spectrometer, but uses an internal steady-state camera to image samples both in real an in k-space (Fourier imaging).
The Kymera is an imaging spectrograph directly coupled to our optical microscope – equipped with three gratings and one mirror, we are able to measure spectrally or spatially resolved emission from the microscope’s sample plane with a time-resolved iCCD camera (2 ns resolution) in the visible spectral range. An alternative beam path enables macroscopic measurements bypassing the microsocpe.
The Phelos is a goniometer-based spectroscopy set-up dedicated to tracking the angle-dependence of the luminescence emitted from thin films upon photoexcitation or from light-emitting devices after electrical injection.
European Fund for Regional Development
Modern light-emitting diodes and organic solar cells: new pathways towards a more sustainable production and use of energy (Nachleuchten)
2024-2027
DFG Major Research Instrumentation Programme
Femtosecond laser spectro-microscopy system
2024
Leverhulme Early Career Fellowship with Matching Funding of the Isaac Newton Trust
Hybrid nanostructures for chiral optoelectronics – polarising communication
2022-2023