High Aspect Ratio Nanostructures for Photothermal Applications

Efficient usage of abundant and free solar energy has immense impact towards the realization of a low carbon and sustainable society. In order to take advantage of solar energy, efficient conversion of light into a usable form of energy, such as electricity or heat, is of great importance. When it comes to the conversion of light to heat or heat to electromagnetic radiation for cooling, a material with high optical absorption or a large absorption cross-section is necessary. Apart from natural materials, artificially-engineered materials, often referred to as metamaterials or metasurfaces, may enable us to tailor the photothermal effect for a desired application. Recently, various nanostructured systems made of plasmonic (metallic) and dielectric materials have been studied. Among them, high aspect ratio nanostructures, whose height are a lot larger than the lateral periodicity, are shown to be effective in improving photothermal heating and radiative cooling. In this chapter, we provide an overview of current progress in photothermal applications on high aspect ratio nanostructures made of dielectric and plasmonic materials, especially titanium nitride.