Our Research

Topics - Equipment - Funding

Our Mission and our Philosophy

three legs beyond traditional disciplines

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.

Our Areas of Expertise

Photophysics & Microscopy

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.

Novel Materials

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.

Optoelectronics

Optoelectronic devices are key building blocks of modern society. Whether it is to harvest sunlight for electricity production or to inject an electric current for light emission, we are keen to study, tailor, and optimise the performance of devices, such as solar cells, light-emitting diodes, and photodetectors.

Much of our research is driven by the goal to create a more sustainable society – we aim to contribute to the quest for better-performing and longer-lasting solar cells, as well as more efficient ways to transform electrical energy into light. A central approach in our lab is to study these devices under operating conditions using our microscopy and specroscopy set-ups.

A further key project is to create pathways to exploit our versatile materials systems for future optical communication platforms, such as through visible light communication.

Impressions from the Lab

Light-Induced Filaments on a Tin-Based Perovskite

Our Equipment

We have access to a broad range of experimental techniques – chiefly via the StranksLab and the wider infrastructure of the Department of Chemical Engineering and Biotechnology, as well as the Cavendish Laboratory at the University of Cambridge.

In addition to the key optoelectronic set-ups detailed below, we make constant use of synthesis and sample preparation hardware in the local chemical laboratories and cleam room.

Confocal PL Microscope

PicoQuant MT200 and SpectraPhysics InSight DS+

The MT200 is mostly used for high resolution fluorescence lifetime imaging. Based on a laser scanning approach, three pulsed internal lasers and a widely tuneable femtosecond laser can be used to excite sample flourescence, which is then detected via two detectors in a TCSPC approach.

Excitation and emission scanning can be decoupled to perform diffusion experiments, and the set-up is equipped with self-built optics to enable wide-field excitation. The femtosecond laser furthermore serves as a powerful source for two-photon absorption.

Hyperspectral microscope

Photon Etc. IMA

The IMA is a powerful wide-field optical microsocpe that generates spectrally resolved micrographs with a 2 nm resolution from the visible to near infrared region. Based on a self-built extension, the set-up is furthermore capable to perform time-resolved measurements for 5-dimensional data acquisiton.

Absolute photometric calibration allows for determining important electro-optical parameters, such as the quasi-Fermi level splitting in solar cells.

Multi-Purpose PL Set-up

Teledyne HRS 500 + PyLoN & PIXIS

This set-up is as powerful as it is versatile. We perform PL spectroscopy and microscopy over the visible and NIR spectral range. A white light source allows for transmission and reflection measurements; polarisation optics render all experiments sensitive to linearly and circularly polarised light.

Microscopy experiments can be performed in focused/wide field excitation & a special lens in the emission path offers access to the Fourier space for back focal plane imaging.

Our Funding

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