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This project focused on a range of sensitisers used in dye sensitised solar cells (DSSC) and tested their suitability in two main areas. The first was the stability of the dye which is essential for the long term success of DSSC devices. The second was to study dye sorption onto mesoporous TiO2 films for the construction of DSSC devices. First the stability of D35, N719, Cyanine, D131, methylene blue and the squaraine 1 and 2 dyes in ethanolic solutions were investigated by exposing to natural light for 64 days. Images after 0 days, 21 days and 64 were processed using RGB analysis and showed significant variation between dye stability. N719 showed the highest stability and squaraine 1 showed the lowest. The stability of N719, squaraine 1 and squaraine 2 was then compared on mesoporous TiO2 films exposed under an artificial light for 4 hours. The results were concordant with the previous data that N719 was the most stable but also showed a higher stability for squaraine 2 than squaraine 1. Finally DSSC devices of N719 and D35 were constructed and exposed to artificial light. The devices were monitored by solar simulation and image analysis. Results confirmed N719 was again the most stable and showed a link between the efficiency and the colour of the device. A process to achieve fast dye sorption to TiO2 films on 15 cm long DSSC devices was developed. The process was conducted by passing the dye through the DSSC device cavity using a peristaltic pump. This method was tested individually with N719, squaraine 2, D131, half squaraine, rhodamine B dyes and also used to co-sensitise half squaraine and SQ1. The time taken for complete sorption was measured using image analysis. Data show that time taken for complete dye uptake varied greatly, with the shortest sorption time of 2 minutes achieved using rhodamine B dye with full coverage after two minutes and a longest sorption time of 1 hour for SQ2. The co-sensitisation of half squaraine and squaraine 1 showed that the order of the dyes was significant, with a dyeing time of 40 minutes for half squaraine first and 50 minutes with SQ1 first.

This project involves on developing highly efficient self-healing polymer systems based on spontaneous copolymerisation. Several different self-healing systems, examples of micro-encapsulation processes, basic concepts of free radical polymerisation and copolymerisation, mechanism and examples of spontaneous copolymerisation, and fracture mechanics of polymeric materials were reviewed. The linear spontaneous copolymerisation of electron donor and acceptor monomers was investigated. Linear copolymers were synthesised by the spontaneous copolymerisation of electron donor monomers (4-methoxy styrene and styrene) and acceptor monomers (maleic anhydride and N-methylmaleimide) in bulk at ambient temperature and at 50 °C. The reaction of 4-methoxy styrene with ethoxymethylene malononitrile was carried out at 50 °C and produced homopolymer of 4-methoxystyrene. The resulting linear polymers were found to be soluble in tetrahydrofuran and acetone and fully characterised by 1D and 2D NMR spectroscopy, SEC, and FTIR. Cross-linked spontaneous copolymerisation of electron donor and acceptor monomers were synthesised. By adding divinylbenzene to 4-methoxy styrene, styrene, N-methylmaleimide, and maleic anhydride, cross-linked materials were obtained. Those materials, as expected, were completely insoluble in normal organic solvent. The cross-linked polymers were characterised by sol-gel technique and FTIR. The micro-capsules were obtained by using urea-formaldehyde micro-encapsulation process. The liquid healing agents (4-methoxy styrene, styrene, divinylbenzene, and their mixtures) were encapsulated using a process involving polymerisation of urea-formaldehyde in oil-water emulsion. The average diameter of the micro-capsule was controlled by adjusting the agitation rate. Micro-capsules with diameter were selected using seivesfor self-healing specimen preparation. The fracture toughness of epoxy matrix was investigated. Fracture toughness of pure epoxy matrix specimen was tested by compact tension geometry. The influence of micro-capsules and solid healing agents on the fracture toughness of epoxy matrix was investigated. The micro-capsules (5-20 wt. %) in the epoxy resin did not change the fracture toughness of matrix. However, solid healing agents MA and MeMal reduced the fracture toughness of epoxy resin as the amount of MA and MeMal added to the matrix. To keep the fracture toughness of specimen closed to that of pure epoxy resin, 10% solid healing was decided to add into the matrix for self-healing preparation. And the fracture toughness of the specimen did not change by adding EtOCN into the epoxy resin matrix. The self-healing performance was assessed by fracture toughness recovery. The self-healing efficiency of those system designed in this project was first evaluated by injecting the liquid healing agents into the crack of the specimen containing solid healing agents. Then, the autonomous self-healing specimen was prepared by adding the micro-capsules and solid healing agents in the epoxy resin matrix. The specimens were subjected to fracture testing to establish healing efficiency. The self-healing system based on obtained good healing efficiency.

Fluorine doped tin oxide (FTO) is widely used as a back contact transparent conducting oxide (TCO) in photoelectrodes for solar energy applications. Using relatively complex methods, a variety of materials can be deposited over FTO to form porous electrodes, which are desired for their higher surface areas. The present work shows how it is conceptually much simpler to template the TCO electrode, producing macroporous electrodes, which allows relatively simple methods to be used to deposit secondary materials for solar water splitting. Macroporous FTO electrodes (macFTO) were fabricated to give highly conductive and structurally ordered electrodes. The fluorine content was analysed using solid state NMR and was found to be as low as 0.5 atom%, 100 times smaller than the precursor Sn:F ratio. The capacitance of electrodes was used to determine the surface area enhancement of macFTO compared to planar FTO (pFTO), which was found to be 12 times greater. As macFTO is an ordered porous, or photonic, electrode, there is a possibility that an increase in light absorption efficiency could be observed. An investigation found that the stop band of macFTO was angular dependent, and the electrode could enhance the lifetime of embedded dyes. The emission lifetime of embedded Rudcbpy, a ruthenium based dye, was found to increase by a factor of 1.8, while the lifetime of coumarin 440/460 was increased by a factor of 1.4 when the stop band overlapped the emission profile of the dye, consistent with literature. Finally, visible light absorbing materials and catalysts for water oxidation were deposited over macFTO, showing that simple techniques could be used to deposit a variety of useful materials. Independently, both BiVO4 and CdS nanoparticles were successfully deposited over macFTO. Only a low CdS nanoparticle loading was required to show that the macFTO electrodes were conductive and capable of supporting photocurrents, with up to a 100 fold increase in the photocurrent density observed compared to equivalent planar electrodes due to the surface area enhancement. The activity of macFTO-BiVO4 electrodes towards water oxidation was then tested with the use of a co-catalyst (CoPi). It was found that the activity of the macroporous electrode was substantially better than equivalent planar electrode, with oxygen evolution rates of 74 μL hr-1 produced with a bias of 1.6 VRHE, and faradaic efficiencies for oxygen evolution reaching 100%.

This thesis reports the development of droplet flow reactors for the preparation of semiconducting polymers, focussing specifically on poly(3-hexylthiophene) (P3HT) pre- pared by Grignard metathesis polymerisation, and random copolymers of P3HT with poly(3-hexylselenophene) (P3HS). In contrast to conventional continuous flow reactors (where the flow consists of a single solvent phase), droplet reactors incorporate an immiscible ’carrier fluid’ that divides the solvent phase into a stream of near-identical microlitre-sized droplets which then pass through the reactor sequentially. In this way, the solvent phase is confined to a well-defined volume that no longer makes contact with the surrounding reactor architecture, and thereby overcomes blockage problems associated with preparation of polymers in continuous flow reactors. To overcome the limited solubility of the Ni(dppp)Cl2 catalyst widely used in Grignard metathesis polymerisation, a more soluble derivative, Ni(dppp)Br2, has been prepared. This catalyst allows P3HT to be synthesised with accurate control over a wide range of molecular weights, even at high throughput (up to 1 kg/day). A scalable ’tube-in-shell’ reactor was developed to provide improved thermal uniformity along the flow reac- tor, enabling the preparation of high molecular weight P3HT with Mw up to 190 kg/mol (PDI 1.5) and lower weight polymers with narrow polydispersity (PDI 1.1). To facilitate multistep chemistries in droplets, a new three-phase methodology is presented that enables the controlled addition of reagents downstream of the original droplet gener- ation. With a view to applying P3HT in electronic devices, an investigation into the influ- ence of polymer purity on the efficiency of P3HT:fullerene bulk heterojunction devices is reported. Polymer purity is shown to have a strong influence over polymer solubility and final device efficiency. With the purest polymers, efficiencies of up to 5.0 % and 7.0 % were obtained with PC60BM and IC60BA, respectively (PC60BM: phenyl-C61-butyric acid methyl ester, IC60BA: indene-C60 bis-adduct). The thesis finishes with the development of a new style of liquid-liquid separator, a key tool for post-processing droplet flows and enabling sequential operations.