Randomly Textured Absorber for Omnidirectional Light Absorption

Abstract Realizing light manipulation with respect to both frequency and angular selectivity is of great significance for sunlight‐to‐heat conversion, but developing a facile and scalable method to enhance light absorption at oblique incidence remains a major challenge. Here a randomly textured absorber is theoretically designed and experimentally achieved by depositing a Ti‐SiO 2 cermet‐based quasi‐optical cavity structure absorber onto a structured stainless‐steel substrate to realize omnidirectional absorption‐enhanced light absorption over a wide incidence‐angle range up to 75°. A strategy is employed of combined chemical etching and sputtering that is suitable for large‐scale production to prepare the randomly textured absorber, which exhibits a near‐complete absorption of 98% at near‐normal incidence. It also shows a remarkable angular absorption of higher than 85% at an oblique incidence angle of 75°, surpassing previously reported absorbers. The absorber's superior angular absorption is ascribed to multiscale scattering on its randomly textured surface and resonance absorption in its quasi‐optical cavity structure. In addition, the randomly textured absorber demonstrates good hydrophobicity, which is beneficial for practical photothermal applications. This appealing strategy highlights a new route for fabricating other omnidirectional absorbers.