A range of novel liquid crystals and amorphous organic conjugated semiconductors were synthesised by the chemistry branch of the Organophotonics group at Hull University. These compounds are studied electrochemically and optically to investigate the suitability of these materials as good donor/acceptor with suitable pairs energy levels for use in organic photovoltaic devices. Liquid crystal compounds with a fluorene-thiophene structure were identified as potential electron donors in combination with perylene based compounds as electron acceptors. Time-of-flight was used to study the charge transport of organic semiconductors in this thesis. The nature of the functional groups of the molecules was found to have a significant influence on the charge carrier mobility. The incorporation of a reactive end group with spacer affected the charge carrier mobility of electron donors negatively, suggesting that the mobility depends on the intermolecular separation. Based on the need to correlate the charge transport of the donor/acceptor blends with photovoltaic devices, the electron and hole mobility were studied for blends. For all blends the hole mobility is lower than that of the pure electron donor. The electron mobility of the blends is much higher than that of the pure electron acceptor. The thermal activation of charge transport in the liquid crystals is investigated by applying the Gill model. The result shows that charge transport in the liquid crystals is thermally activated and the activation energy is field dependent. The Gaussian disorder model and correlated disorder model were used to analyze the mobility data of four liquid crystals compounds with the same conjugated core and different end groups. We show that the thin film nanoscale morphology and the phase separation of the donors/acceptors blends depend on the chemical structures of donors and acceptors, the casting solvents and the annealing temperature of the film. The functional groups of the perylene bisimide are found to influence the roughness. The surface roughness of the blended thin film is minimum and its phase separation finest when the electron donors component has short terminal aliphatic groups rather than long polymerisable chains. Chlorobenzene shows the best performance as coasting solvent. The annealing temperature is significant in controlling the nanoscale morphology and the phase separation of an intermixed network of the blends. We successfully demonstrate photovoltaic performance using blends of our novel donors and acceptors. The annealing temperature is very important to optimise the solar cell performance by optimisation of the phase separation. The perylene based liquid crystals have disappointing performance as electron acceptors. The donor with the shortest terminal end group gives the best result. The device performance fully correlates with the blend nanoscale morphology of the blends; the blend with the smallest domains gives best power conversion efficiency; the best device has a value of 1.1%.

Microphysical and dynamical interactions between aerosols and clouds are associated with some of the largest uncertainties in projections of future climate. Many possible aerosol effects on clouds have been suggested, but large uncertainties remain. In order to improve model projections of future climate, it is essential that we improve our quantitative understanding of anthropogenic aerosol effects. Several studies investigating interactions between satellite-observed aerosol and cloud properties have been published in recent years. However, the observed relationships are not necessarily due to aerosol effects on clouds. They may be due to cloud and precipitation effects on aerosol, meteorological covariation, observational data errors or methodological errors. An analysis of methodological errors arising through climatological spatial gradients is performed. For region sizes larger than 4°×4°, commonly used in the literature, spurious spatial variations in retrieved cloud and aerosol properties are found to introduce widespread significant errors to calculations of aerosol-cloud relationships. Small scale analysis prior to error-weighted aggregation to larger region sizes is recommended. Appropriate ways of quantifying relationships between aerosol optical depth (τ) and cloud properties are considered, and results are presented for three satellite datasets. There is much disagreement in observed relationships between τ and liquid cloud droplet number concentration and between τ and liquid cloud droplet effective radius, particularly over land. However, all three satellite datasets are in agreement about strong positive relationships between τ and cloud top height and between τ and cloud fraction (f_c). Using reanalysis τ data, which are less affected by retrieval artifacts, it is suggested that a large part of the observed f_c-τ signal may be due to cloud contamination of τ. General circulation model simulations further demonstrate that positive f_c-τ relationships may primarily arise due to covariation with relative humidity, and that negative f_c-τ relationships may arise due to scavenging of aerosol by precipitation. A new method of investigating the contribution of meteorological covariation to the observed relationships is introduced. Extratropical cyclone storm-centric composites of retrieved aerosol and cloud properties are investigated. A storm-centric description of the synoptics is found to be capable of explaining spurious f_c-τ relationships, although the spurious relationships explained are considerably smaller than observed relationships.

This thesis describes the use of counterpropagating pulse trains to quasi-phase-match high-harmonic generation (HHG). Two novel techniques for generating trains of ultrafast pulses are described and demonstrated. The first method makes use of a birefringent crystal array to split a single pulse into a sequence of pulses. The second method makes use of the time-varying polarisation of a chirped pulse passed through a multiple-order wave plate to generate a train of pulses by the addition of a polariser. It is demonstrated that this second technique can be used to make pulse trains with non-uniform pulse separation by using an acousto-optic programmable dispersive filter to manipulate the higher-order dispersion encountered by the chirped pulse. The crystal array method is used to demonstrate quasi-phase-matching of HHG in a gas-filled capillary, using one and two counterpropagating pulses. Enhancements of up to 60% of the intensity of the 27th harmonic of the 800,nm driving laser light are observed. Information on the spatial and dynamic properties of the HHG process is obtained from measurements of the coherence length in the capillary. Simulations of HHG in a capillary waveguide have been performed. These agree well with the results of the quasi-phase-matching experiments. The effect of mode-beating on the generation process in a capillary and its use as a quasi-phase-matching mechanism are investigated.