Azulene-based Dyes for Dye Sensitised Solar Cells

Abstract

This thesis studies the synthesis of azulene-based donor--acceptor organic dyes for application as the sensitising component of dye sensitised solar cells (DSSCs). Ruthenium (II) polypyridyl complexes have been widely studied and have been used to great success during the past 25 years; however, ruthenium is scarce and expensive. Ruthenium-free dyes have been the subject of intense research globally, and organic, metal-free dyes are attractive substitutes for ruthenium (II) sensitisers because of the wide availability of the starting materials and low cost.Azulene is a simple, blue-coloured hydrocarbon with a ground-state dipole and a tendency for electron transfer between its seven- and five-membered rings. Its electronic and photo-physical properties and its ability to support a positive charge while remaining partially aromatic make it an interesting proposition for use in photovoltaic cells.This thesis begins by discussing the rationale behind and design of DSSC sensitisers using azulene as the electron donor in a donor-electron rich  linker-acceptor push-pull dye structure. Extended Hückel molecular orbital calculations are used to identify potential molecular structures. The thesis goes on to describe the synthesis of the identified target molecules to produce a range of azulene-based dyes over three separate iterations or generations, with the second and third generations designed to build on and enhance the dyes created in the earlier generations.Electrochemical and spectroscopic studies are used to assess the suitability of the dyes synthesised for use in DSSCs and, for the first two generations, DSSCs are fabricated and evaluated to determine the effect of structural variations on photovoltaic efficiency. Finally, a crystallography study examines the molecular structure of the azulene-based dyes and discusses the geometry of the molecules with reference to their use in DSSCs.

Date of Award	6 Dec 2017
Original language	English
Awarding Institution	University of Bath
Supervisor	Simon Lewis (Supervisor) & Petra Cameron (Supervisor)