High-performance ultra-simple solar absorber with extremely high tolerance for fabrication errors

Broadband metamaterial perfect absorbers have drawn considerable attention from researchers for a broad range of applications in electromagnetic stealth, solar energy harvesting and other fields. However, it is extremely challenging to integrate the excellent characteristics of ultra-broadband, perfect absorption, polarization independent, and insensitivity to wide incidence angles into a structurally simple absorber. Herein, we present an ultra-wideband solar perfect absorber with an ultra-simple structure, which consists of a Si3N4-Ti-Si3N4-Ti fourlayer structure. The optimized structure offers more than 92 % absorption in the bandwidth range of 450-2750 nm, and the average absorption is up to 97.3 %. Moreover, we elaborate the physical mechanism to achieve the broadband perfect absorption. For solar thermal systems, the absorber is capable of absorbing 95.7% of the sunlight, its blackbody radiation absorption is as high as 98.0 % at 1900 K and it has a photothermal conversion efficiency of 90.2 % at 1000 K. Furthermore, the absorber displays the characteristics of being independent of polarization and insensitive to wide incidence angles. Additionally, the absorber possesses a very high tolerance for manufacturing errors. It is shown that the designed absorber is ultra-simple in structure and excellent in performance, and has excellent application prospects in fields including solar thermal conversion.