Up/down conversion of energy using molecular semiconductors offers an enticing opportunity to improve solar cell efficiency beyond the Shockley Queisser limit. Up/down conversion in organic semiconductors is achieved using singlet exciton fission (SF) and its reverse, triplet-triplet annihilation (TTA) to overcome thermalization losses or harvest low-energy photons, respectively. In SF, an absorbed photon is converted into two lower energy excitations which, if harvested by a solar cell by-pass thermalization losses. In TTA, two lower energy molecular excited states are combined into a higher energy excitation which emits a photon thereby harvesting low-energy photons. To date, much research has focused on the underlying physical mechanism and molecular design rules for both processes. However, recent research highlights the importance of sample morphology and microstructure in controlling SF or TTA. This project aims to develop a detailed understanding of the morphology- and microstructure-dependence of SF and TTA in molecular systems using a range of different transient spectroscopy and microscopy measurement techniques.
I am seeking to hire PhD students to work on projects across the physics/chemistry/biology interface. My group’s expertise lies in tracking electronic excited states with time-resolved spectroscopy as they move through molecules, pigment-protein complexes, photonic structures and organic semiconductor devices. I offer a dynamic and international work environment with world-class facilities in a city famed for its beautiful countryside and city-wide cultural events.
You will learn how to fabricate thin films of organic semiconductors with different sample morphologies using evaporation and spin-coating. You will learn how to characterize the morphology of the thin films using grazing-incidence wide-angle X-ray scattering (GIWAXS) and atomic force microscopy (AFM). In a second phase, you will use a variety of time-resolved and steady-state spectroscopy and microscopy techniques to determine how excited-state processes depend on morphology and microstructure. During this process, you will learn how to perform ultrafast spectroscopy and to build optical setups in Sheffield’s Lord Porter Ultrafast Laser Facility. You will also learn data analysis of big data sets and programming (mainly Python).
You will have a 2:1 or above (or equivalent degree) in physical chemistry, physics or material science. I am looking for hard-working and enthusiastic students.