In recent times, plasmonics has been a hallmark in improving optoelectronic device performance as well as in improving sensing. Confining light in dimensions below the diffraction limit and subsequently converting the incident photons into localized charge-density oscillations called localized surface plasmons, optical enhancements of the local fields by many orders of magnitude is possible. This dissertation explores the use of such surface plasmon resonances in core multishell nanostructures and demonstrates the values of such structures in energy harvesting and sensing. Additionally, it also shows the use of emerging plasmonic materials like metal nitrides (TiN, ZrN) instead of traditional plasmonic materials (Au, Ag) in the nanostructure designs. Utilizing the localized surface plasmon resonance (LSPR) in metallic components of core multishell nanowires, calculations of the local density of states as a measure of emission were made using a Green’s function method, while the absorption and scattering were simulated using the Mie formalism. Combining both the absorption and the emission, the quantum efficiency of white LEDs was calculated and the optimal material/dimensions for maximal performance was determined for different phosphor components in a white LED. Additionally, the use of ZrN as a plasmonic cloak for noise cancellation in Si photodetectors is shown and the performance is compared with an Au cloak. Using the developed methodology, it is proved that ZrN cloaks can outperform Au cloaks in a certain region of the visible spectrum, showing the benefit of using such plasmonic systems in place of traditional materials. The fabrication of the different components of the core multishell nanowires is also presented, and in particular, fabrication of ultra-thin (sub-10 nm) plasmonic TiN is achieved. Utilizing plasmon hybridization, a tunable double resonance feature is observed in Au/SiO2/Au core shell shell (CSS) nanoparticles, which have been then demonstrated to improve the photocatalytic performance in hematite. In particular, the double resonance peak allows absorption of light beyond the band gap of hematite and subsequent conversion into photocurrent through hot electron injection. Comparison has been made with Au nanoparticles, and it has been shown that the CSS nanoparticles outperform Au nanoparticles significantly. These CSS nanoparticles have also been used for bioimaging, in particular for Raman spectroscopy, with strong results at high densities of the nanoparticles. Utilizing stronger scattering SiO2/Au Nanoshells, it has been possible to work towards single particle imaging of molecules and demonstration of this phenomenon has been shown here through the use of coherent Raman scattering spectroscopy.

>Magister Scientiae - MSc / This thesis starts with the reviewing of studies on the loading of noble metals and nanostructured metal oxides into bulk heterojunction organic solar cell device architectures. The reviews focused on the innovative developments in the use of various fullerene derivatives as electron acceptors in organic solar cells. It additionally reflected on the effect of metallic nanoparticles (NPs), such as gold (Au) and silver (Ag), on the performance of organic solar cells. Besides the metallic NPs, the effect of metal oxide nanoparticle loading, e.g. CuO, ZnO and TiO2, on the organic solar cell performance, and the use of noble metals doped TiO2 on the gas sensing application were reviewed. / 2024

Absolicon is a pioneering solar technology development company specializing in the manufacturing and selling of advanced solar energy systems engineered to generate renewable energy for diverse use. Comprising essential components such as reflectors (mirrors) and a solar receiver tube, these solar energy systems are equipped to efficiently capture and convert solar irradiation into usable thermal energy. As an integral facet of an ongoing research, this project will contribute to optimize the reflection and absorption capacity in receiver tubes of Absolicon's solar collectors. The aim is to investigate optically selective plasmonic coatings intended as an undercoating in the solar selective surfaces. The main coating material that will be used and analysed is gold due to its plasmonic properties and inert nature as well as its low toxicity. The gold will be coated on stainless steel using physical vapor deposition (PVD) and then annealed at mid-to-high temperatures to produce a plasmonic surface. The effect of Au thicknesses, annealing times/temperature and will be investigated to optimize the coating with regards to optical properties based on a systematic method called Design of Experiments (DoE). The goal for the gold coating is to increase the reflectance in the infrared region while generating a plasmonic absorption peak in the visible region (the position and width will be optimized), making it a more beneficial surface to coat a solar selective surface than the original stainless steel (SS). It was found that the size and inter-particle distance of GNPs depend on the temperature and annealing time for different thickness. The surface analysis from SEM-images and AFM-topographs provided that samples with smaller grains are more likely to exhibit significant plasmonic effects compared to larger grains. According to the surface characterization, either thinner gold coating exposed to high temperature for short annealing time or thicker gold coating with longer annealing time provide plasmonic absorption peak in visible light region.