Electrochemical characterisation of surface modified semiconductor electrodes and quantum dots

The development of more efficient photovoltaic devices is crucial in order to harness the abundant solar energy reaching the planet each day. Recent years have seen major advances in the production of solar cells, based on bulk or nanostructured semiconductors. The aim of this thesis is to further the fundamental understanding of electron transfer processes across quantum dots (QDs). The effect of common particle stabilising ligands on the electrochemical behaviour of the dots will be investigated by studying QDs and also self-assembled monolayer modified semiconductor single crystals. The valence band edge of 3-mercaptopropionic acid (MPA) stabilised CdTe QDs was investigated electrochemically using a rotating disc electrode in order to reduce diffusion effects. It was revealed that the MPA induced a surface dipole, shifting the band edge position of the particles. CdTe quantum dots assembled at blocked electrodes shed light on the processes involved in nanoparticle mediated electron transfer. The alignment of the quantum dot band edges with the fluctuating energy levels of the redox species in solution allows the fine-tuning of the electron transfer processes. CdS single crystal electrodes modified with self- assembled monolayers of organic molecules which are generally used in the stabilisation of quantum dots were investigated as a model system to understand the effect of stabilising ligands on the electrochemical and photoelectrochemical properties of quantum dots. The findings reported in this thesis add to the greater picture of the study of electron transfer processes across nanostructures and shed light on the effect of adsorbed organic molecules on the electrochemical and photoelectrochemical properties of quantum dots and bulk single crystals.EThOS - Electronic Theses Online ServiceGBUnited Kingdo