Randomly Textured Absorber for Omnidirectional Light Absorption

摘要

Realizing light manipulation with respect to both frequency and angular selectivityis of great significance for sunlight-to-heat conversion, but developinga facile and scalable method to enhance light absorption at oblique incidenceremains a major challenge. Here a randomly textured absorber is theoreticallydesigned and experimentally achieved by depositing a Ti-SiO_2 cermet-basedquasi-optical cavity structure absorber onto a structured stainless-steel substrateto realize omnidirectional absorption-enhanced light absorption overa wide incidence-angle range up to 75°. A strategy is employed of combinedchemical etching and sputtering that is suitable for large-scale productionto prepare the randomly textured absorber, which exhibits a near-completeabsorption of 98% at near-normal incidence. It also shows a remarkableangular absorption of higher than 85% at an oblique incidence angle of 75°,surpassing previously reported absorbers. The absorber’s superior angularabsorption is ascribed to multiscale scattering on its randomly textured surfaceand resonance absorption in its quasi-optical cavity structure. In addition,the randomly textured absorber demonstrates good hydrophobicity, whichis beneficial for practical photothermal applications. This appealing strategyhighlights a new route for fabricating other omnidirectional absorbers.