Purely organic molecules usually absorb or emit (fluorescence) light only via their singlet states because transitions to the triplet state are ‘forbidden’.  However, in organometallic complexes with heavy metals such as iridium or platinum strong relativistic effects (such as spin-orbit coupling) mean that transitions to and from triplet states are allowed. However, at this stage it is not possible to predict or even explain why some complexes perform very well, e.g., are highly luminescent while others with only slight structural changes are not. We have been working on a method that will allow this to be done for the first time. The projects in this area will compare the solutions of the Schrodinger and Dirac equations to study the role of relativistic quantum-mechanical effects in the materials to expla

...Read more

There are two key elements that control the efficiency of a solar cell. How many electrons can we generate for a given illumination level (sunlight) and how much useful work can we get out of those electrons. In this project we study the transport of electrons through organic solar cells using a mixture of mathematical and computational modelling. We will seek to answer questions such as do the electrons hop or tunnel through the active layers, what is the energy costs associated with such transport, and are there molecular designs that can optimise the processes....Read more

Imagine that we are having a dinner party. We have decided to seat our guests around a table so that each person has a member of the opposite sex on either side of them. If I have a square table and four guests this is not difficult. However, if we have a triangular table and three guests it is impossible. In an antiferromagnet the electrons want to sit with their spins pointing in the opposite direction to their neighbours. Again this is straightforward to arrange on a square lattice but impossible to achieve on the triangular lattice. This effect is known as frustration....Read more

Wilson’s renormalisation group is often regarded as the most important idea in physics from the second half of the twentieth century. It has had profound influence in fields as disparate as condensed matter physics and high-energy particle physics. One of the key ideas of the renormalisation group is that rather than study the full Hamiltonian of the system of interest, which is usually intractable, one should study an effective low energy Hamiltonian. An effective Hamiltonian is derived by ‘integrating out’ the high-energy degrees of freedom of the system....Read more