Broadband enhancement of light harvesting and photocatalytic devices

Abstract

We considered the structure with a roughened metallic film on the bottom and a roughened TCO glass layer on the top, separated by a thin dielectric layer. We fabricated experimental structures and simulated them by the finite element method. Thus, we verified that the combined influence of two rough films significantly improves light trapping within the dielectric layer between them while plasmonic effects lead to concentration of electromagnetic field into volumes much smaller than a single wavelength. Consequently, the radiation intensities are proportionally increased, even for several orders of magnitude, compared to the incident beam. Another interesting property observed is that the structure continues to act as a diffractive light trap well into the UV region and simultaneously as a plasmonic superabsorber for IR light, turning the increase of TCO opaqueness with wavelength into a benefit since it significantly expands the useful spectral range. Tuning of dopant levels in TCO or using different metals or alloys together with varying coarseness of the films can further be used to tailor the electromagnetic response.