Enhancement of Solar Spectrum Absorption in Single Graphene Sheets Using a Plasmonic Nanoantenna.

In this paper, we present a periodic nanostructure based on two types of silver plasmonic nanoantennas in order to enhance light absorption in graphene with a wavelength between 300 nm and 1800 nm. In this structure, a single graphene layer is located between two hexagonal boron nitride (hBN) layers, where this set is sandwiched between two layers of SiO₂. The first nanoantenna type is a trapezoid inside SiO₂, adjacent to the lower hBN, which focuses light within the graphene layer by intensifying the localized surface plasmons, triggering a significant increase in the absorption of the solar spectrum by graphene. The extent of this increase changes with varying bases of the trapezoid. The second nanoantenna type is in the same structure and contains two unequal trapezoids adjacent to each other. By adjusting the bases of these trapezoids, a relatively uniform broadband absorption spectrum is achieved which significantly enhances light absorption in the solar spectrum within 300–1800 nm, as compared to the first nanoantenna type. Both the first and second types of nanoantenna provide appropriate absorption at a communication window of 1550 nm as well as at 850 nm and 1300 nm, respectively. [ABSTRACT FROM AUTHOR]