Photothermal materials that convert sunlight into heat are crucial for solar evaporation. The field advanced significantly, leading to the development of various materials with improved light absorption capabilities, including metallic nanostructures, semiconductors, carbon-based materials, and conjugated polymers [1, 2]. Although many reviews covered photothermal materials [3–9], this section highlights the design principles, material types heterojunctions, and the nanoengineering and fabrication processes of solar absorbing materials.