Exciton Topology and Dynamics in CdSe Clusters: Effects of Ligands and Aggregation from Electronic Structure Computation

Quantum dots (QD) are an object of continuous interest because of their usage in various technology applications, such as QLED, new and innovative photovoltaic cells, to quantum computing. This interest is due to the possibility to work with systems that have modulable discrete energy levels, and so can be used as building blocks to create nanostructured materials with optimised properties for the application of interest. The aim of this thesis is to investigate the electronic structure of inorganic clusters that could be referred to as colloidal semiconductive QD (CQDs) in terms of composition and structure but with fewer total atoms. This, in order to be able to do a fully atomistic study of the problem, instead of the more commonly used parametric models. The effect given by different ligands on the electron density in dimeric systems (and up to small aggregates), especially on the densities of the excited states, is a focus of this work, to achieve a better comprehension and give a more detailed description of the mechanisms involved in the excitonic delocalisation and the nature itself of excited states such as the topology of the delocalisation and potential charge transfer (CT) involved. In this study, by the acquisition of specific knowledge of methods to compute the electronic structure of complex chemical systems, the tools to explore these systems are obtained, in order to gain new insights and to be able to optimise structures with electronic properties suitable to maximise energy and charge transport.