Design and Fabrication of Multiscale Metallic Structures to Enhance Photothermal Conversion Efficiency

Abstract

Photothermal devices have recently garnered significant attention owing to their high development potential. The primary mechanism behind photothermal conversion is the transformation of incident light into thermal energy through a nonradiative process. However, maximizing heat retention without thermal losses remains challenging. In this study, multiscale metallic structures were fabricated with a thermal insulation layer to enhance the photothermal effect. Metal-assisted chemical etching and the photoetch technique were adopted to fabricate the microstructures and nanostructures on silicon substrates to produce multiscale structures. The architecture of the multiscale structures was also optimized to increase the light absorption. Subsequently, a thin oxide film was generated conformally on the multiscale structures by applying a thermal process. Finally, titanium nitride, which is a photothermal material, was deposited onto the multiscale structures with the oxide layer. The oxide layer served as a thermal barrier that effectively isolated heat conduction and reduced the optical reflection. The proposed multiscale metallic structures demonstrated outstanding photothermal conversion, achieving a temperature increase of up to 60 °C under an irradiance of 66 mW/cm² (0.66 sun), which surpasses results reported in recent literature. The experimental results indicated that the optimized multiscale metallic structures were significantly advantageous in photothermal conversion. This study can be useful in future applications, such as solar energy conversion and photothermal catalysis.