Broadband high-temperature metamaterial absorber and thermal emitter composed of fractal geometry

Fractal structures are natural patterns that repeat themselves. They have several unique features that make them ideal for solar energy absorption and sensing applications. In this study, we present a high-performance, polarization insensitive solar absorber comprises of a nickel (Ni)-made hash-shaped fractal geometry develop over a thin layer of gallium-doped zinc oxide (GZO) features a high absorption rate that covers the visible and near-infrared wavelengths of the spectrum. The results show that broadband aggregative absorptivity of 92% is attained between 380 nm and 3850 nm attributed to remarkable localized surface plasmon resonance (LSPR) induced by the periodic array of Ni nano-resonators and surface plasmon resonance (SPR) at the interface of GZO-SiO₂ layers. Further, the absorptivity remains above 90% from 670 nm to 3850 nm over a bandwidth of 3180 nm. With the utility of high-temperature resilient materials in the developed metamaterial structure, it shows potential for the thermal applications; as the results indicate the maximum heat radiation efficiency is 92.88% at 1600 K. Aside from that, we provide insight into the broadband high solar light capturing characteristics of the proposed device with the support of surface current density and electric field distribution study at the selective wavelengths. Furthermore, the device’s parametric study revealed a minor impact on its absorptivity/emissivity characteristics while also suggesting its robustness, which could be useful in device manufacture process. The overall benefits of the proposed device show its potential for high-temperature solar energy harvesting applications and solar thermophotovoltaic (STPV) cells.