One of the natural tendencies of photovoltaic technologies is the systematic reduction of the thickness of the solar cells in order to reduce the cost, to save rare or toxic elements or to limit recombination. So far, crystalline thin-film (GaAs) and poly-crystalline (CIGS) technology are reaching optimum conversion efficiency for thicknesses around 1 or 2 microns. Typically, this thickness range does not require new solutions of optical trappings as it is the case for amorphous silicon. However, if we want to reduce these thicknesses by a factor of 10 or even 100 to study new concepts of collections and conversions (GaAs or GaSb) or reduce the use of indium (CIGS), new needs for efficient light absorption are necessary for these technologies. This manuscript is focused on the design, simulation and realization of innovative nanophotonic solutions for future ultra-thin crystalline solar cells.As a first step, we were engaged in an approach at odds with the usual design of solar cells to trap light in a ultra-thin (≤100 nm) layer of material (GaAs, GaSb and CIGS). We propose an array of metal nanostructure placed in front of the cell, transferred on a metal mirror in order to obtain a high, multi-resonant absorption independent of the angle of incidence and polarization. Numerical analysis of the resonant mechanisms involved was conducted as well as the fabrication and optical characterization of demonstrators. The results of this study are motivating for future work on the ultra-thin devices, involving new concepts of collection (ballistic transport) or conversion (hot carrier solar cells).On the other hand, we studied the possibility of integrating a rear gold nanostructured back contact (200-400 nm) in thin CIGS solar cells to potentially increase the current of short circuit and open circuit voltage. We have proposed an innovative process to achieve this structure and the optical trapping for CIGS solar cells. Numerical study, manufacture of demonstrators and first measurements are presented.

Gold nanoparticles were deposited onto a silicon substrate using electroless deposition. The process was optimized by adjusting the deposition time, the temperature of the plating solution, the amount of time that the silicon was exposed to hydrofluoric acid, and the concentration of the plating solution. The nanoparticles deposited on the silicon were characterized using scanning electron microscopy. The optimized electroless deposition process was then used to modify the surface of silicon solar cells with gold nanoparticles for enhanced power generation. Spectral response and I-V curve tests were performed on the modified solar cells to quantify the enhancements. The modified surfaces of the silicon solar cells were characterized by scanning electron microscopy and reflectance measurements. The electroless deposition process was also used to generate nanostructures for surface-enhanced Raman scattering (SERS). A template-nanohole array was fabricated on silicon by focused ion beam milling. Gold nanoparticles were deposited in the holes of the template, resulting in interesting gold-nanodoughnut structures. The gold nanodoughnuts were examined by scanning electron microscopy, and their potential as SERS substrates were tested using Rhodamine 6G as a molecular probe under 633 nm laser excitation. / Graduate / 0494 / 0485 / mmillard@uvic.ca

Dye-sensitized solar cells (DSSCs) present an interesting method for the conversion of sunlight into electricity. Unlike in other photovoltaic technologies, the difficult tasks of light absorption and charge transport are handled by two different materials in DSSCs. At the heart of the DSSC, molecular light absorbers (dyes) are responsible for converting light into current. In this thesis the design, synthesis and properties of new metal-free D-π-A dyes for dye-sensitized solar cells will be explored. The thesis is divided into six parts: Part one offers a general introduction to DSSCs, dye design and device characterization. Part two is an investigation of a series of donor substituted dyes where structural benefits are compared against electronic benefits. In part three a dye assembly consisting of a chromophore tethered to two electronically decoupled donors is described. The assembly, capable of intramolecular regeneration, is found to impede recombination. Part four explores a method for rapidly synthesizing new D-π-A dyes by dividing them into donor, linker and acceptor fragments that can be assembled in two simple steps. The method is applied to synthesize a series of linker varied dyes for cobalt based redox mediators that builds upon the experience from part two. Part five describes the synthesis of a bromoacrylic acid based dye and explores the photoisomerization of a few bromo- and cyanoacrylic acid based dyes. Finally, in part six the experiences from previous chapters are combined in the design and synthesis of a D-π-A dye bearing a new pyridinedicarboxylic acid acceptor and anchoring group. / <p>QC 20140509</p>

With an increasing demand for renewable energy sources, research efforts on different solar cell technologies are increasing rapidly. The dye-sensitized solar cell (DSC) is one such technology, taking advantage of light absorption in dye molecules. The liquid based DSC contains several interesting and important interfaces, crucial for the understanding and development of the solar cell performance. Examples of such interfaces include dye-semiconductor, electrode-electrolyte and solute-solvent interfaces. Ultimately, complete interfaces with all these components included are of particular interest. One major challenge is to understand the key functions of these systems at an atomic level and one way to achieve this is to use an element specific and surface sensitive tool, such as photoelectron spectroscopy (PES). This thesis describes the use and development of PES for studying interfaces in the DSC. The materials part of the thesis focuses on interfaces in DSCs studied with PES and the methodology development parts focus on methods to use PES for investigations of solvated heterogeneous interfaces of interest for photoelectrochemical systems such as the DSC. More specifically, beginning with standard vacuum techniques, dye molecules bound to a semiconductor surface have been studied in terms of energy level alignment, surface coverage and binding configuration. To increase the understanding of solvation phenomena present in the liquid DSC, liquid jet experiments have been performed in close combination with theoretical quantum calculations. As a step towards an in-situ method to measure a complete, functioning (in operando) solar cell, methodology development and measurements performed with higher sample pressures are described using new high pressure X-ray photoelectron spectroscopy techniques (HPXPS).

The scalable syntheses of functional, porous nanostructures with tunable three-dimensional morphologies is a significant challenge with potential applications in chemical, electrical, electrochemical, optical, photochemical, and biochemical devices. As a result, several bio-enabled and synthetic approaches are explored in this work (with an emphasis on peptide-enabled deposition) for the generation of aligned nanotubes of nanostructured titania for application as electrodes in dye-sensitized solar cells and biofuel cells. As part of this work, peptide-enabled deposition was used to deposit conformal titania coatings onto porous anodic alumina templates under ambient conditions and near-neutral pH to generate aligned, porous-wall titania nanotube arrays that can be integrated into dye-sensitized solar cells where the arrays displayed improved functional dye loading compared to sol-gel-derived nanotubes. A detailed comparison between synthetic and bioorganic polyamines with respect to titania film properties deposition rate provided valuable information for future titania coating experimental design given specific applications. The development of template-based approaches to single-wall titania nanotube arrays led to the development of a new synthetic method to create aligned, multi-walled titania nanotube arrays. Lastly, peptide-enabled deposition methods were extended beyond inorganic mineral and used for enzyme immobilization by cross-linking the peptide with the multicopper oxidase laccase. Peptide-laccase hybrid enzyme coatings improved both the amount of enzyme adsorbed onto carbon nanotube “buckypaper” and allowed the enzyme to retain more activity upon immobilization onto the surface.

Gold nanoparticles were deposited onto a silicon substrate using electroless deposition. The process was optimized by adjusting the deposition time, the temperature of the plating solution, the amount of time that the silicon was exposed to hydrofluoric acid, and the concentration of the plating solution. The nanoparticles deposited on the silicon were characterized using scanning electron microscopy. The optimized electroless deposition process was then used to modify the surface of silicon solar cells with gold nanoparticles for enhanced power generation. Spectral response and I-V curve tests were performed on the modified solar cells to quantify the enhancements. The modified surfaces of the silicon solar cells were characterized by scanning electron microscopy and reflectance measurements. The electroless deposition process was also used to generate nanostructures for surface-enhanced Raman scattering (SERS). A template-nanohole array was fabricated on silicon by focused ion beam milling. Gold nanoparticles were deposited in the holes of the template, resulting in interesting gold-nanodoughnut structures. The gold nanodoughnuts were examined by scanning electron microscopy, and their potential as SERS substrates were tested using Rhodamine 6G as a molecular probe under 633 nm laser excitation. / Graduate / 0494 / 0485 / mmillard@uvic.ca

No description available.

This thesis aims to investigate different infrared absorbing molecules and how their properties are affected by their incorporation into polymer nanoparticles. Metal-free phthalocyanine-H2Pc, uranyl super phthalocyanine-USPc, and europium bisphthalocyanine were studied-EuPc2; the latter two capable of IR absorption. Due to the discovery of USPc’s moisture sensitivity, only H2Pc and EuPc2 were derivatized to facilitate encapsulation in polystyrene nanoparticles through a miniemulsion polymerization. These novel phthalocyanines attained loadings of up to 41wt% and exhibit substantial broadening of absorption peaks. Furthermore, the EuPc2 loaded particles also reveal an unprecedented gain in extinction coefficient of the NIR and radical absorption peaks. The leaching behavior of the dye was also studied, as this had not been undertaken in the literature, and revealed the need for a method of polymerizing/chemically binding phthalocyanines into nanoparticles; with preliminary steps taken to realize this goal.

Organic solar cells (OSCs) are of interest because the technology offers a significant opportunity to reduce the overall costs of solar energy. OSCs can be very inexpensive to produce given that they rely on non-commodity materials and can use existing manufacturing techniques that are not labour- and capital-intensive. In this research, a financial model, named TEEOS (Technological and Economic Evaluator for Organic Solar), is developed and is used to determine financial indicators, such as simple payback period. These indicators are used to determine technical objectives for the OSCs. Two sample cells are evaluated in Toronto, Canada using historical data. The results show that the cell with a higher efficiency and wider absorptive wavelength range produces a payback period of approximately nine years, while the other cell has a payback period well over 45 years. Stochastic modeling techniques are also used to better replicate electricity price and weather fluctuations.

This thesis aims to investigate different infrared absorbing molecules and how their properties are affected by their incorporation into polymer nanoparticles. Metal-free phthalocyanine-H2Pc, uranyl super phthalocyanine-USPc, and europium bisphthalocyanine were studied-EuPc2; the latter two capable of IR absorption. Due to the discovery of USPc’s moisture sensitivity, only H2Pc and EuPc2 were derivatized to facilitate encapsulation in polystyrene nanoparticles through a miniemulsion polymerization. These novel phthalocyanines attained loadings of up to 41wt% and exhibit substantial broadening of absorption peaks. Furthermore, the EuPc2 loaded particles also reveal an unprecedented gain in extinction coefficient of the NIR and radical absorption peaks. The leaching behavior of the dye was also studied, as this had not been undertaken in the literature, and revealed the need for a method of polymerizing/chemically binding phthalocyanines into nanoparticles; with preliminary steps taken to realize this goal.