Study of a perfect solar absorber from the visible to the near-infrared band using particle swarm optimization

In this study, we simulate how much solar energy a proposed planar dielectric-metal (SiO2-Ti-SiO2-Ti-SiO2-Ti-SiO2-W) structure can absorb by employing FDTD solutions. The proposed structure is ultrathin (510.1 nm). It can absorb incident light within a wavelength range of 345 to at least 2500 nm with an average absorption of 97.8% for the incident light in the 345-2500 nm band while maintaining efficient absorption for a wide range of incident light when its angle changes and being insensitive to the polarization angle of the incident light. In addition, the Particle Swarm Optimization algorithm was used to optimize the proposed planar structure, and the optimality of the 8-layer structure was investigated. In addition, we compare the proposed structure to those of others, analyze the reasons for the structure's perfect absorption, and discuss the resonance mode that occurs during the absorption process, which demonstrates the rationale behind its perfect absorption. As a result, the proposed device can efficiently and sustainably collect solar energy.