Research

Research

Our research centres on the use of several different variants of continuous-wave and pulse EPR spectroscopy for the characterisation of the nature and dynamics of spins in materials and devices for energy applications, with a current focus on organic photovoltaics. We also aim to further advance the EPR technique through improved experiments, data analysis protocols and simulation tools.

Charge separation in organic photovoltaics

Paramagnetic species involved in the photovoltaic mechanism in organic photovoltaics studied by EPR

The conversion of solar energy to electricity in organic solar cells relies on photoinduced charge separation at the interface between donor and acceptor domains. The photovoltaic mechanism therefore involves a series of paramagnetic states that can be investigated by EPR: the charge-transfer state, separated charges and triplet states.

We use transient and pulse EPR techniques combined with theoretical simulations and modelling to follow the charge separation process and to characterise the charge-separated states generated in state-of-the-art donor-acceptor blends.

 

Spin-dependent processes investigated by Electrically Detected Magnetic Resonance

Electrically Detected Magnetic Resonance on miniature photovoltaic devices

Electrically Detected Magnetic Resonance (EDMR) allows extension of the EPR technique from materials to fully functional devices. Instead of detecting magnetisation, EDMR detects changes in current flowing through a device as a response to microwave excitation.

We build miniature organic solar cells and use EDMR to study spin-dependent processes directly involved in current generation.

 

Method development in EPR spectroscopy

EPR method development and simulation

Advancements in EPR spectroscopy underpin the ability to address new challenges and gain new insights. We are exploring the use of shaped microwave pulses for the design of pulse EPR experiments with improved sensitivity and information content, focusing in particular on techniques for the characterisation of spin-correlated radical pairs.

We also contribute to the development of improved tools for the simulation of EPR data, which allows us to interpret our experimental results in terms of the properties of the systems and the fundamental processes we are investigating.