A tungsten-based solar absorber with a strip-combined starfish structure with high photothermal conversion efficiency and low radiative heat loss.

We propose a tungsten-based broadband resonator capable of achieving near-perfect solar absorption with suppressed radiative heat loss. Across the entire solar radiation spectrum, the absorber exhibits a spectrally integrated total solar absorptance of 95%. Taking into account the thermal emission under an operating temperature of 100 °C, the photothermal conversion efficiency remains as high as 92-93%. Using particle swarm optimization, the initial square-based structure is transformed into adjacent and closely packed strip structures with multiple lengths to achieve enhanced solar absorption. The analysis uses finite-difference time-domain simulations, considering light polarization, incident angle, and structural defects. We proposed a new metamaterial structure with multiple strips that are more efficient and have a simpler geometric structure, as compared to multilayer films, pyramids, or cone structures, which mostly exhibit substantial radiative heat losses. The structure is composed of a W/SiO2/W (metal-insulator-metal) configuration, with a surface nanostructure pattern composed of low-emissivity tungsten, with fabrication error-tolerant computational design.