Ultrafast spectroscopy of single crystal organic semiconductors
Organic semiconductors are exciting materials. They are not only starting to compete with traditional (opto)electronic materials in device applications, they are also intrinsically sustainable. Solution-processed organic photovoltaics, for example, use ~10 times less energy to produce than any other PV technology and are only made from earth-abundant elements.
Until recently, it was thought that the problem with organic semiconductors was disorder, thought to be a fundamental draw-back of solution-based (i.e. sustainable, low-cost) deposition techniques. Work in the last 4 years has changed this paradigm. Solution-processed highly ordered single crystals now demonstrate field-effect mobilites above 10cm2/Vs. Only 10 years ago such ultra-high mobilities at room temperature in thin organic films would have been considered unachievable by many experts in the field.
These new ultra-high mobility thin films pose a considerable challenge to our understanding of charge and energy transport. They operate in what is known as the ’intermediate coupling’ regime where energy and charge transfer can be described as being somewhere between the band-like transfer that occurs in highly ordered inorganic semiconductors and the purely hopping transfer that occurs in very disordered systems.
In this project, you will measure materials from collaborators in Japan using Sheffield’s new laser facility to attempt to describe the energy transport and radiative and non-radiative deactivation in the intermediate coupling regime. It is expected that you will collaborate with theoreticians in the USA to develop models to interpret the data.