Imidazole ionic liquid based ultra-broadband metamaterial absorbers with a concave–convex structure

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Abstract In this paper, the ionic liquid (IL) 1-ethyl-3-methyl-imidazolium dicyanamide was employed to construct an ultra-broadband metamaterial absorber (ILMMA), leveraging a Concave–Convex (C–C) design paradigm (C–C ILMMA). The simulation results showed that the C–C ILMMA has more than 90% absorption efficiency in the frequency band of 4.00–50.00 GHz, and the relative bandwidth reaches 170.4%. To find out the absorption mechanism of the C–C ILMMA, the electromagnetic (EM) field distribution and power loss density are employed to analyze the absorption resonance peak, the impedance matching theory is also used to reveal the mechanism of the structure to achieve broadband absorption. Meanwhile, the C–C ILMMA demonstrates a wide incident angle, polarization insensitive characteristics, and its absorption performance is also excellent in the range of 25 °C–100 °C. Because the photosensitive resin used in the absorber is environmentally friendly, low cost, and the mass of the ‘task-specific’ ILs is lighter than that of metal, the designed C–C ILMMA has broad application prospects in EM energy collection and invisibility technology.