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This thesis explores the structure-property relations in different nanostructured materials. Nanostructured polymer blends with interpenetrating network morphology of donor and acceptor materials have been considered ideal for organic bulk heterojunction photovoltaics. In this work we mainly investigate the self-organization of polymer blends via crystallization to generate functional nanostructures for organic electronics. Controlling morphology of organic photovoltaic thin films is crucial for the optimization of the device performance as there is a fine balance of exciton generation and separation as well as charge transport. To better understand the bulk heterojunction morphology, we first investigated the structure formation of poly (3-hexylthiophene) (P3HT)/ phenyl-C61- butyric-acid methyl ester (PCBM) system. Crystallization-induced phase separation has been found to drive the formation of a nanostructure in the blends, the size of which is determined by the intrinsic 10 nm length scale of semicrystalline P3HT. The mixing of PCBM within amorphous P3HT interlayers does not disrupt the crystallinity of the P3HT. P3HT crystallization expels PCBM into the spherulitic interlamellar amorphous layers, where it enriches to its miscibility limit. Above the solubility limit, PCBM aggregates start to form. The results suggest that the crystallization of P3HT and the enrichment of PCBM in interlamellar regions give rise to interconnected donor and acceptor phases those are close to the optimal bulk heterojunction structure. This structure formation mechanism is manifested by the good photovoltaic performance of spherulitic P3HT/PCBM films. Structural studies of P3HT/poly[(9,9-dioctyfluorene)-2,7-diyl-alt-(4,7-bis(3-hexylthien-5- yl)-2,1,3-benzothiadiazole)-2', 2"-diyl] (F8TBT) are presented. P3HT/F8TBT system exhibits a crystallization-driven structure formation similar to the P3HT/PCBM system despite the existence of a miscibility gap. The lamellar crystallization of P3HT is not perturbed by the addition of F8TBT. X-ray scattering studies indicate that F8TBT is mixed in the interlamellar amorphous phase up to a solubility limit, while a bulk heterojunction framework is established by the crystalline lamellae of P3HT. The excess F8TBT is accommodated at amorphous grain boundaries as well as the film/substrate interface. The structural studies are correlated with the photovoltaic device performance of P3HT/F8TBT films which exhibit spherulitic morphology. Devices based on spherulitic films show moderate efficiencies with improved fill factors but decreased photocurrents in comparison to that of thermal annealing condition. The results suggest that the nanostructure formation in P3HT/F8TBT blends is determined by the crystallization of P3HT, resulting in a structural size that are beneficial for exciton dissociation, while the F8TBT segregation at the substrate interface impair the device performance. The phase separation behavior in crystalline/crystalline blends consisting of P3HT and polyethylene oxide (PEO) is investigated. The self-assembly of P3HT in solution induces vertical segregation in blend films, in comparison to typical lateral polymer phase separation structures from non-aggregated solutions. Thin film transistors based on P3HT/PEO blends show show a nearly undegraded charge carrier mobility at low P3HT content due to the formation of a layered structure with P3HT nanowire networks segregated at the dielectric surface. Finally, a diversion from morphology studies of polymer blends involves the biomimetic fabrication of hierarchical fibrillar structures to achieve gecko adhesion. The hierarchical structures were fabricated based on polymer pillars tipping with carbon nanotube forests. The adhesion performance of the polymer-carbon nanotube hierarchical structures was tested by shear force measurements.

The goal of the work presented in this thesis, was to develop inorganic material systems synthesized via organic precursors and to pattern them using different lithographic techniques. The materials investigated were the ferromagnetic Ni metal and the mesoporous TiO2 and Nb2O5, which have applications in dye sensitized solar cells. The first part of the thesis presents an overview of pattern formation in organic and inorganic materials and the working principles of dye sensitized solar cells. Next the theoretical background of block-copolymer and block-copolymer structure directing hybrid materials are described. Fundamental knowledge of magnetism and ferromagnetism are also presented. The techniques used to characterize the material and the fabricated devices are detailed. For example, the samples were characterized using magnetic force microscopy (MFM) and scanning electron microscopy (SEM), while the materials were characterized by BET. The fabrication of Ni metal films using sol-gel process is then discussed. The Ni metal films were patterned with sub-10 nm wide lines via direct-writing electron beam lithography, and their electrical resistivity was investigated. The in uence of mesoporous TiO2 obtained using a block-copolymer, which acted as a structure-directing agent for the metal oxide, is then presented. This material was incorporated into solid state dye sensitized solar cells. The development of a mesoporous material fabrication protocol, which has significantly in uenced solar cell efficiency, is discussed. Finally the general ideas and some preliminary results on a mesoporous Nb2O5 material and its application in dye sensitized solar cells are presented.

The ever increasing level of penetration of Distributed Generation (DG) in power distribution networks is not without its challenges for network planners and operators. Some of these challenges are in the areas of voltage regulation, increase of network fault levels and the disturbance to the network protection settings. Distributed generation can be beneficial to both electricity consumers and if the integration is properly engineered the energy utility. Thus, the need for tools considering these challenges for the optimal placement and sizing of DG units cannot be over emphasized. This dissertation focuses on the application of a soft computing technique based on a stochastic optimisation algorithm (Particle Swarm Optimisation or PSO) for the integration of DG in a power distribution network. The proposed algorithm takes into consideration the inherent nature of the control variables that comprise the search space in the optimal DG sizing/location optimisation problem, without compromising the network operational constraints. The developments of the proposed Multi-Search PSO algorithm (MSPSO) is described, and the algorithm is tested using a standard, benchmarking 69-bus radial distribution network. MSPSO results and performance are compared with that of a conventional PSO algorithm (and other analytical and stochastic methods). Both single-objective (minimising network power loss) and multi-objective (considering nodal voltages as part of the cost function) optimisation studies were conducted. When compared with previously published studies, the proposed MSPSO algorithm produces more realistic results since it accounts for the discrete sizes of commercially available DG units. The new MSPSO algorithm was also found to be the most computationally efficient, substantially reducing the search space and hence the computational cost of the algorithm compared with other methods, without loss of quality in the obtained solutions. As well as the size and location of DG units, these studies considered the operation of the generators to provide ancillary voltage support to the network (i.e. with the generators operating over a realistic range of lagging power factors, injecting reactive power into the network). The algorithm was also employed to optimise the integration of induction generation based DG into the network, considering network short-circuit current ratings and line loading constraints. A new method for computing the reactive power requirement of the Abstract V induction generator (based on the machine equivalent circuit) was developed and interfaced with the MSPSO to solve the optimization problem, including the generator shunt compensation capacitors. Finally, the MSPSO was implemented to carry out a DG integration problem for a real distribution network and the results validated using a commercial power system analysis tool (ERACS).

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