Our research focuses on the photophysics of organic optoelectronic materials and nanodevices. We develop state-of-the-art ultrafast laser spectroscopy tools to observe and control molecular-scale dynamics in plastic solar cells, flexible transistors, quantum-dot photodetectors and other functional nanosystems. The prospective work includes charge-transport properties of proteins, ultrafast switching of organic transistors, and time-resolved spectroscopy on the scale of single molecules.
Organic Solar cells
The recent emergence of non-fullerene acceptors has pushed the efficiency of organic solar cells to 14 %. We employ ultrafast pump-probe (transient absorption spectroscopy) and "pump-push" techniques to study the fundamental processes (e.g. exciton dissociation, charge generation, recombination and transport) that govern high-performance materials and devices.
Structural and electronic dynamics in perovskites
At the forefront of optoelectronics research are the metal-halide perovskites. The photophysical properties of these hybrid materials are intrinsically linked to vibrations of the lattice. Understanding the role of structural dynamics immediately following photoexcitation is of critical importance to the continued development of perovskite-based materials and devices. Examples of work in our group include two-dimensional infrared spectroscopy to monitor vibrational/rotational lattice motions, and pump-push-probe spectroscopy to track hot-carrier cooling.
Atoms and molecules are in constant motion. In crystals and other ordered systems, this motion typically takes the form of distinct and discrete vibrations within the crystal lattice, termed phonons. This project aims to utilise ultrafast spectroscopy to understand how these phonons affect the flow of current through organic semiconducting materials with an aim to understand, and eventually exploit these vibrations for a broad array of applications.
Ultrafast electrochemistry and solar fuels
Artificial Phsotosynthetic systems based on transition metal oxides, such as Fe2O3 or Cu2O, can be used to store solar energy as fuels in the form of chemical bonds. The absorption of light in these systems triggers a cascade of transformations ranging from changes in oxidation state to distortions of the atomic structure. These changes happen within femtoseconds following light absorption and determine the properties of the photocatalytic material. We use spectroscopic techniques based on X-Ray and IR radiation to probe these ultrafast transformations and correlate them with catalytic activities. Using X-rays, we are able to probe changes in the electronic structure of metal oxides and elucidate which correlations impact device performance. Using IR "pump-push" techniques, we can determine photocurrent loss mechanisms in photoelectrochemical devices and elucidate how control of vibrational modes can help improve catalytic yields.