Flexible broadband plasmonic absorber on moth-eye substrate

High efficiency, broadband and flexible plasmonic absorbers comprised of top Ag nanoparticle layer, SiO2 dielectric slab and bottom Ag reflective layer on moth-eye polydimethylsiloxane substrates were fabricated by sputtering. The moth-eye polydimethylsiloxane substrates were obtained by simply replicating the pattern of the commercial U-shaped anodic aluminum oxide templates. For our designed absorber, the integrated absorption efficiency over the wavelength range from 350 nm to 1000 nm at normal incidence is optimized to 95.8% when the nominal thickness of the top Ag nanoparticle layer is 5.4 nm and the thickness of the SiO2 slab is 96 nm. In addition, our absorber performs angle-insensitively with the integrated absorption efficiency suffering only around 10% degradation when the incidence changes from normal to 60 degrees oblique. Moreover, the absorber is very robust against bending and the integrated absorption efficiency almost maintains its original value even after bending for 10, 000 times. Compared to the absorbers fabricated on a flat substrate, the absorbers made on the structured moth-eye substrates have high tolerance of the thickness of the SiO2 slab. Simulation results indicate that the Ag nanoparticle layer allows light penetrate into the corrugated dielectric slab, forming various photonic resonances at different wavelengths, resulting in efficient light harvesting over a broadband wavelength range. (C) 2017 Elsevier Ltd. All rights reserved.