Highly efficient metamaterial solar energy absorber from UV to NIR regime

We theoretically propose and experimentally demonstrate an ultra-broadband metamaterial absorber (MA) based on a quadrilayer structure, comprising a Cr-SiO₂-Ge cube array atop a Ge-Cr base film. The geometric parameters were optimized using a hybrid particle swarm optimization (PSO) and gradient descent algorithm. The resulting absorber exhibits a simulated average absorption of 95.1%, which is matched by a measured average absorption of 84.1% across the ultraviolet to near-infrared spectrum (200-2000 nm). The simulated absorber exhibits a 90% absorption bandwidth of 1413 nm (587-2000 nm), along with polarization insensitivity and excellent angular stability under both TE and TM modes. Furthermore, quantitative analysis reveals a high solar-weighted absorption of 91.8%. Finally, the efficient generation of photoelectrons and hot carriers-facilitated by the Ge and Cr layers, respectively-highlights the device's potential for applications in solar energy harvesting, photodetection, and photothermal conversion.