Improving range of SPR tunability and extinction efficiency of spheroidal silver nanostructures in graphene environment

Abstract

In photovoltaics, the materials having ability to manipulate the optical fields and coupling of energy flow inside the device play a crucial role. In this article, we report the role of graphene environment on spheroid-shaped Ag nanoparticles (NPs) with various shapes and sizes. This study confirms the tunability of surface plasmon resonances (SPRs) and an enhancement in extinction efficiency, derived numerically using discrete dipole approximation (DDA). We have chosen oblate-and prolate-shaped Ag NPs for the numerical experiment and analysed their optical signatures in terms of extinction efficiency and SPR tunability against the quasi-static approximation. The excitation of longitudinal and transversal resonances was also observed because of the asymmetric shape of Ag NPs. All optical responses have been analysed by varying the effective radii and aspect ratio of Ag NPs, and the thickness of graphene monolayer (from 0.1 to 0.5 nm). Tunability of longitudinal resonances has been observed in the 600-833 nm wavelength region, while for transversal resonances, the tunability is in the 450-505 nm wavelength range. The results represent the effect of graphene environment on the tunability of SPRs with enhanced extinction efficiency. This study could lead to the development of a photovoltaic device with wide range of tunability and enhanced efficiency.