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We show a hybrid structure consisting of Si film with photonic crystal surface and random triangular gold grooves reflector at the bottom, which is capable of realizing efficient, broad-band, wide-angle optical absorption. It is numerically demonstrated that the enhanced absorption in a broad wavelength range (0.3-9.9 μm) due to the scattering effect of both sides of the structure and the created resonance modes. Larger thickness and period are favored to enhance the absorption in broader wavelength range. Substantial electric field concentrates in the grooves of surface photonic crystal and in the Si film. Our structure is versatile for solar cells, broadband photodetection and stealth coating. [ABSTRACT FROM AUTHOR]

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 (0.3–9.9 μm). 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. [ABSTRACT FROM AUTHOR]