Plasmonic-Decorated TiO₂ Thin Films as Photocatalytic Anti-Soiling Coatings

Soiling of solar collectors represents one of the most pressing challenges for the reliability and efficiency of solar energy systems, particularly in arid and semi-arid regions such as the Middle East and North Africa (MENA). The accumulation of dust, sand, and organic residues on solar surfaces leads to substantial reductions in power output and escalates operational and maintenance (O&M) costs, often making soiling the single largest contributor to performance losses in photovoltaic (PV) plants. Soiling on PV modules is broadly categorized into inorganic and organic components, each posing distinct challenges. Inorganic soiling, typically derived from mineral-rich sources such as desert sand, sea salt, and suspended mineral particles, tends to be less adhesive and can often be removed through routine cleaning or wind action. In contrast, organic soiling, originating from airborne dust mixed with pollen, microbial deposits, and biological residues such as bird droppings, exhibits strong adhesion to surfaces. Organic matter is particularly problematic as it not only resists removal but can also serve as a substrate for microbial growth, leading to corrosive byproducts that degrade encapsulants, coatings, and even glass surfaces over time. To address this critical issue, the present study investigates the use of plasmonic metal nanoparticles (NPs) as a strategy for mitigating the impact of organic dust deposition on solar surfaces. Specifically, the work evaluates the role of localized surface plasmon resonance (LSPR) in enhancing photocatalytic degradation of organic contaminants. Gold (Au) nanoparticles were deposited onto plain glass and TiO₂- coated glass substrates via the solid-state dewetting (SSD) process, which enables the formation of uniformly distributed nanoscale particles with strong plasmonic activity. The SSD approach also maximizes the nanoparticle–substrate interface, thereby promoting efficient charge transfer and improved catalytic reactivity under solar illumination. The experimental results demonstrated that the incorporation of Au nanoparticles significantly enhances the photocatalytic activity of TiO₂, leading to a pronounced reduction in the organic fraction of deposited dust. This effect is attributed to the excitation of LSPR in Au NPs, which increases light absorption and generates hot electrons that actively participate in photocatalytic reactions at the surface. As a result, organic contaminants decompose more efficiently, reducing adhesion and facilitating easier removal. These findings highlight the potential of plasmonic nanostructures to serve as the foundation for next-generation anti-soiling coatings, combining optical transparency with self-cleaning functionality. By targeting the persistent problem of organic soiling, often the most difficult to mitigate in real-world PV deployments, this approach provides a promising pathway toward reducing cleaning frequency, lowering O&M costs, and ensuring higher long-term energy yields in desert and coastal environments.