Ultra-broadband absorber based on algorithmic optimization of MgF2–Fe stacked structure

Broadband absorbers possess a wide array of potential applications, including electromagnetic cloaking, solar energy harvesting, and solar power generation. However, achieving excellent ultra-broadband absorption with plasma-metal materials remains challenging due to their inherently narrow bandwidth. To tackle this issue, we propose an ultra-broadband absorber, free from lithography, composed of a multilayer stack of magnesium-iron fluoride (MgF2–Fe). In this study, we optimized the structural parameters of the absorber using a particle swarm optimization algorithm to achieve theoretically optimal absorptivity. Numerical simulations revealed that the absorber achieved an impressive theoretical average absorption of 98.4% across a broad wavelength range from ultraviolet to near-infrared (321–1800 nm). Importantly, it exhibited stable absorption performance at large incidence angles (0–70°), while maintaining high absorption efficiency. Furthermore, it demonstrated polarization independence at perpendicular incidence angles. Subsequently, experimental preparations and tests were conducted on absorber samples to evaluate their solar energy absorption capacity. Both experimental and theoretical comparisons underscored the promising potential of this structure for applications in solar energy collection, conversion, and solar power generation. •Material simplicity: Just use MgF2 and Fe to make the preparation of multiple materials much less complicated.•Inverse design: optimisation of structural parameters using PSO algorithm.•Lithography-free design: Flat film design facilitates large-area preparation.•Excellent absorption performance: High absorption characteristics and high efficiency of light and heat conversion.