Light harvesting in nanofabricated hybrid plasmonic-2D semiconductors

The research conducted during my PhD was focused on the development of large-area nanophotonic solutions based on metallic and dielectric materials to enhance light absorption in ultrathin and two-dimensional (2D) absorbers. These approaches are designed to increase the performance of optoelectronic, photonic, and photovoltaic applications. A significant aspect of the work involved the study of photochemical and photoelectrochemical processes, including photocatalysis and water splitting, with titanium dioxide (TiO₂) as the active layer. Although TiO₂ demonstrates high photocatalytic activity and stability, its absorption is restricted to the ultraviolet (UV) spectrum, requiring the development of strategies to extend its functionality into the visible range. In parallel, two-dimensional transition metal dichalcogenides (2D-TMDs) were investigated due to their tunable bandgap and high optical absorption in the visible spectrum. A scalable synthesis method was developed for MoS₂-WS₂ heterostructures, which exhibit a staggered band alignment, facilitating charge separation and improved photocatalytic efficiency. To enhance light absorption, two scalable approaches were explored. The first involved metallic nanostructures fabricated through a self-organized ion beam sputtering (IBS) technique, producing gold nanowires that leverage localized surface plasmon resonances (LSPR) to enhance light harvesting. A low-energy IBS process was also optimized to fabricate smooth, conductive metallic films, offering an alternative to commercial transparent conductive electrodes (TCEs). The second approach focused on "flat optics" through periodic nanostructured templates fabricated via laser interference lithography (LIL). These templates enhance light absorption through Rayleigh Anomaly (RA) effects, demonstrating applicability with both amorphous and crystalline TMD films. This research contributes to the development of scalable, industrially viable light-harvesting strategies for renewable energy conversion and environmental applications.