New metamaterial as a broadband absorber of sunlight with extremely high absorption efficiency

We present computer simulations on the design and performance of a broadband and extremely highly efficient (similar to 98%) CMOS-compatible metamaterial nanostructure for solar energy applications. An optimized unit cell of the nanostructure consists of a 300 nm x 300 nm x 100 nm titanium nitride (TiN) base covered with 60 nm thick SiO2. A 50 nm high TiN disk of 90 nm radius sits over the SiO2 dielectric. The TiN disk is capped with another disk of HfO2 of 90 nm radius and 30 nm height into which six Au nanoparticles (NPs) are symmetrically placed. A periodic array of such unit cells of 300 nm periodicity covers an underlying solar panel. We investigate the performance of the absorber as functions of wavelength, angle of incidence, and polarization of incident sunlight by utilizing the COMSOL Multiphysics software. We observe an impressive absorption of approximately 98% for normal incidence and the broadband range of wavelengths from 250 nm to 1100 nm. Additionally, the absorption is almost independent of the polarization of light and remains higher than 90% for a wide range of incidence angles.