Band alignment optimisation for enhanced inorganic thin film photovoltaics
Semiconductor thin films are the basis of the lowest cost per Watt solar cells. While these technologies are well established, there remains tremendous scope for improvement and further cost reduction through optimization of their material properties and the use of more earth abundant materials to increase sustainability. One area which is significantly under-investigated is the role of the electronic interface in these technologies. The band alignments at semiconductor interfaces are known to be of critical importance to electronic performance but little in the way of consistent analysis has been performed to study this. This PhD project aims to address this by directly investigating the impact of the interface electronic properties and by developing design principles for tuning the interface properties to improve performance in solar cells. The project will involve both the deposition of semiconductor thin films by physical vapour deposition techniques and photoemission measurements of ionization potential, work function and band offsets of semiconductor surfaces and interfaces. This fundamental analysis will be used to improve the design of solar cell devices by determining optimal band alignments. New and sustainable photovoltaic devices will then be fabricated in our dedicated device laboratory and characterized in our nanomaterials characterization and photoemission laboratory. Several established device platforms are available at Liverpool as a test bed for the band alignment optimization strategies that are developed. These include CdTe, Sb2Se3 and inorganic perovskites. The studentship includes the opportunity to spend up to six months undertaking research with our collaborators at the National Renewable Energy Labs in Colorado, USA.