Year

2005

Degree Name

Doctor of Philosophy

Department

Department of Chemistry - Faculty of Science

Abstract

The utilisation of conducting polymers for photovoltaic applications represents the possibility of low-cost production of solar electricity. The chemical modification of the precursors used to prepare conducting polymers provides an avenue to the tuning of the photovoltaic, rheological and solubility properties of conducting polymers to suit photovoltaic applications. Poly(thiophene)s have been widely utilised by researchers in the field of conducting polymer photovoltaics. The present study in part considered the utilisation of a range of thiophene precursors, in particular terthiophene derivatives, for the preparation of polymeric photoactive layers within photoelectrochemical cells. These precursors included a C60-substituted terthiophene derivative, 3-alkylthiophenes and ethersubstituted terthiophenes. Polymers synthesised from 3-alkylthiophene derivatives were also blended with a soluble C60 derivative to give composite films. Terthiophene itself was used to prepare photoelectrochemical cells based on poly(terthiophene). The effects of the conditions used to electrochemically grow poly(terthiophene), such as solvent, electropolymerisation technique and electropolymerisation temperature, were investigated. In addition, the incorporation of commercially available anionic dyes and cationic dyes into poly(terthiophene) during electropolymerisation and post-growth electrochemical reduction, respectively, was considered. The investigations made in this study may be classified according to one of the following strategies for improving the photovoltaic efficiency of photoelectrochemical cells based on poly(thiophene)s: controlling polymer morphology, enhancing light absorption, improving exciton dissociation or increasing the efficiency of electron transfer at the interface between the photoactive layer and liquid electrolyte. In this way the investigations in this study were all targeted at improving a particular aspect of the photovoltaic effect in photoelectrochemical cells. In addition to the characterisation of the photovoltaic properties of the photoactive materials prepared, such materials were also characterised using techniques that included post-growth cyclic voltammetry, UV-Vis spectroscopy, photocurrent action spectroscopy, scanning electron microscopy and in situ spectroelectrochemistry. The results obtained from such characterisations gave an insight into the photovoltaic properties observed, in addition to general information on the properties of the photoactive materials investigated.

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