Design of Graphene-Based Core/Shell Nanoparticles to Enhance the Absorption of Thin Film Solar Cells

Plasmonic nanoparticles have had a great impact on the enhancement of the absorption of the thin film solar cell. In this study, we propose two core/shell nanoparticles including graphene/Ag and Ag/graphene nanoparticles. For the design of the graphene/Ag nanoparticle, we utilize a graphene quantum dot (GQD) with a diameter of 66 nm as the core and cover it with Ag with a thickness of 1 nm. We compute the permittivity of the GQD based on the Cole–Cole model. For the design of the Ag/graphene nanoparticle, we cover a spherical Ag nanoparticle with a diameter of 66 nm with a graphene layer with a thickness of 1 nm. We model the surface conductivity of the graphene layer based on the Kubo formula. We consider both nanoparticles as homogeneous nanoparticles and obtain their permittivity based on the equivalent dielectric permittivity model. We incorporate these nanoparticles into an optical simulator and extract their scattering cross sections alongside the Ag nanoparticle. The graphene/Ag nanoparticle shows the best scattering performance; meanwhile, Ag nanoparticle has the weakest scattering performance. Then, we design a Si-based thin film solar cell with Ag nanoparticle and compute its characteristics through the FDTD method. Then, we replace the Ag nanoparticle with our nanoparticles. The short-circuit current density (J_sc) of the Si-based cell improves by 26.3% by embedding of Ag nanoparticle in the absorber layer. This improvement increases by embedding of graphene/Ag and Ag/graphene nanoparticles to 35.3% and 36.8%, respectively.