Abstract Photocatalysis, combined with renewable energy sources, is one of the main methods for achieving sustainable development. Plasmonic structures have been shown to enhance the efficiency of photovoltaics, motivating similar advancements in photocatalysis. Stochastic structures provide a broadband optical response and do not require lithography for fabrication. We analyzed four types of stochastic plasmonic structures: gold nanoparticles, gold nanoparticles on a thick gold film, rough gold film, and a stochastic metasurface (thin gold film over a rough substrate). Nanoparticle radii range from 10 nm to 50 nm (uniform size distribution), while gold films are between 10 nm and 100 nm thick. Geometries are procedurally generated and used for numerical modeling in the 400 nm to 900 nm spectral range, depending on the type of semiconductor material deposited on top, TiO2 (wide bandgap semiconductors) or silicon (narrow bandgap semiconductors). We show that across the entire spectral range, only about 10% of the total absorbed optical energy is used for carrier generation in semiconductor material when using nanoparticles alone. Thus, the plasmonic effect is primarily used for hot electron generation and photothermal effects, depending on particle size, even in narrowband semiconductors. For the remaining three structures, this efficiency increases to 30% for thicker films and 40% for ultrathin films. This is due to decoupling surface detail size (nanoparticle size) from the intensity of optical absorption by using surface-bound plasmonic modes instead of relying solely on resonant particle modes. Additionally, these three types of structures allow further adjustments in overall size, volume distribution, and layer thickness depending on the structure type, which influences internal processes and, consequently, hot carrier generation and heating effects, with minimal impact on the structure’s efficiency.
Obradov et al. (Mon,) studied this question.
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