Tight-binding treatment of conjugated polymers

This PhD thesis concerns conjugated polymers which constitute a constantly growing research area. Today, among other things, conjugated polymers play a role in plastic based solar cells, photodetectors and light emitting diodes, and even today such plastic-based components constitute an alternative to the corresponding traditional silicon-based semiconductor components. If plastic based semiconductor components within the foreseeable future meet the expectations of combining high quality with limited production costs, then plastic based components are going to play a substantial role in the electronic industry of tomorrow. This thesis specifically treats the three conjugated polymers trans-polyacetylene (tPA), poly(para-phenylene) (PPP) and poly(para-phe\-nylene vinylene) (PPV). The present results, which are derived within the tight-binding model, are divided into two parts. In one part, analytic results are derived for the optical properties of the polymers expressed in terms of the optical susceptibility both in the presence and in the absence of a static electric field. In the other part, the cumputationally efficient Density Functional-based Tight-Binding (DFTB) model is applied to the description of phonons and polarons in the above-mentioned polymers. The first part of the thesis contains the theoretical foundation for the presented results.