Randomly Textured Absorber for Omnidirectional Light Absorption

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-SiO₂ 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.