Enhancement of solar absorption by a surface-roughened metal-dielectric film structure

A solar selective absorber with a multilayered SiO2 (87.0 nm)/Cr (8.3 nm)/SiO2 (96.3 nm) film structure was designed and fabricated by magnetron sputtering on a surface-roughened copper (Cu) substrate. The proposed structure can enhance solar absorption by combining both the typical solar absorption designs of the textured surface and metal-dielectric multilayer film structure. The measured solar absorptance is about 94%, which yields an enhancement of about 2% accompanied by a slightly higher thermal emittance than that observed for the surface-smoothed structure. The increasing thermal emittance of the surface-roughened film structure is expected to markedly cancel the advantage of absorptance enhancement as the temperature increases to 600 K, implying that the proposed film structure functions more efficiently at low or intermediate temperatures (<600 K). (C) 2017 The Japan Society of Applied Physics