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A method was developed to access the interior of light-guiding structures in order to exploit the enhanced sensing potential of the highly confined electromagnetic field distributions, located within the core of a waveguide. The work presented in this thesis explores therefore the possibilities of optical waveguide spectroscopy utilising transparent mesoporous thin-film waveguides deposited on top of athin gold layer. These multi-layer assemblies are employed in a prism-coupling attenuated total internal reflection (ATR) configuration. The angular read-out of the reflected light intensity allows label-free detection schemes with high sensitivity to changes of the dielectric environment in the case of the presence of analyte molecules within the probing region. This optical waveguide spectroscopy technique has been used to study the real-timediffusion of Ruthenium 535-bisTBA (N-719) dye into mesoporous nanocrystalline titaniumdioxide films. The porous films were prepared on top of gold substrates and prism coupling was used to create a guided wave in the nanocrystalline film. Dying was carried out by bring the film into contact with a 3 x 10-4 moldm-3 dye solution and using optical waveguide spectroscopy to monitor the change in both the refractive index and theextinction coefficient of the nanoporous layer as dye diffused into the porous network. Dyeuptake in a 1.27 μm film was slow with the refractive index of the film still increasing after 22 hours.

Dye design is one of the most important and challenging areas in dye-sensitised solar cell research. The purpose of the work in this thesis is to synthesise and characterise novel ruthenium(II) and copper(I) dyes that will provide insight into the number of binding groups required and the potential use of chromophoric ligands. A series of four simple Ru(II) dyes have been synthesised with the general formula Ru(4,4’- (R)-bipyridine)2(NCS)2 where R represents CH3 or CO2H. The study investigates the number of acid groups required to successfully bind to TiO2 whilst maintaining efficient charge injection. The series consists of one acid group, two acids, two acids on adjacent bipyridines, and three acids groups. Dye uptake was studied via optical waveguide spectroscopy, providing information on dye diffusion, adsorption and desorption kinetics, and surface coverage. Interestingly, the two acid groups on adjacent ligands suggested poor/slow binding to TiO2 surface and a high degree of dye aggregation in comparison to two acid groups on the same ligand. The dye with three binding groups showed strong adsorption to TiO2 and better dye coverage, resulting in a high efficiency. The complexes were all fully characterised by electrochemistry, photoluminescence, absorption spectroscopy, DFT calculations and solar cell performance testing. To date, there has been limited exploration of copper(I) complexes as potential alternatives to ruthenium(II) sensitisers, with even fewer publications reported for Cu(I) heteroleptic species. The neutral complexes that were synthesised are of the general formula: Cu(4,4’- (R)-6,6’-(CH3)-bipyridine)(β-diketonate) and Cu(4,4’-(R)-6,6’-(CH3)-bipyridine)(dipyrrin) where R represents CH3 or CO2Et. Additional blocking groups on the ligands are introduced to minimise structural change during oxidation or MLCT excitation. Improved stability and reproducibility have been shown for complexes containing the dipyrrin ligand, likely due to better steric constraints and better π-overlap with the bipyridine. There has also been a remarkable improvement in light absorption, from 450 nm to 600 nm. In-situ solar studies have been carried out on the Cu(4,4’-(R)-6,6’-(CH3)-bipyridine)(dipyrrin) series and a 0.41% efficiency has been achieved. Computational studies supports the experimental data in which the main transition appears to be ligand centred (dipyrrin) with a small MLCT contribution.

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