Efficient broadband energy absorption based on inverted-pyramid photonic crystal surface and two-dimensional randomly patterned metallic reflector

Abstract

We propose a hybrid structure containing photonic crystal surface with inverted-pyramid arrays on the top, two-dimensional (2D) patterned metallic reflector with random pyramids’ sizes at the bottom, and a Si film between the two layers, to achieve high-efficiency, broad-band and wide-angle energy absorption. Due to the scattering effect and waveguide mode resonance effect of the structure, the enhanced absorption is close to or even surpasses the Yablonovitch limit in a broad wavelength range (0.3–9.9μm). What’s more, the high absorption efficiencies are insensitive to the variation of incidence angle (from 0° to 80°) and substantial electric field modes concentrate in the inverted-pyramid arrays and Si film. Comparing to un-patterned film and one-dimensional (1D) patterned film, 2D-patterned film obtains higher absorption efficiency for both s polarization and p polarization. Furthermore, we find that the high absorption band expands to a broader wavelength range with the size of structure increasing. Our multifunctional structure is experimentally feasible and is expected to have a wide application in the areas of energy harvesting, energy conversion, energy conservation and sustainable energy utilization.