Comparative study of silver nanoparticles embedded in dielectric layers for solar cell application

Light trapping induced by plasmonic metal nanoparticles is of extensive interest for photovoltaics. In this paper, plasmonic effect of silver nanoparticles embedded in dielectric layers hybrid structures on c-Si photoactive absorbing material is presented. Dielectric SiN_x and SiO₂ layers were considered and deposited by plasma enhanced chemical vapor deposition (PECVD) and electron beam evaporation (EBE) respectively. Silver nanoparticles were prepared by annealing of thermally evaporated silver thin films ranging from 5 to 25 nm in N₂ gas atmosphere at 260 °C for an hour. For comparative study, thicknesses of each layer including silver thin flim, SiN_x spacer layer and c-Si wafer were varied to attempt preliminary judgement of the appropriate structure. It is shown that reflection near bandgap of Si can be reduced while silver nanoparticles are fabricated on SiN_x layer and covered by SiO₂ layer. By comparing the morphologies of nanoparticle arrays resulted from different thicknesses of silver thin film, it is indicated that nanoparticle arrays with large average sizes and high surface coverage on the front surface can greatly increase undesirable reflection in visible wavelength region in spite of their advantage in reflection reducing at longer wavelength. In addition, light trapping of the hybrid structures for varying thicknesses of SiN_x spacer layer and c-Si wafer were also investigated respectively. Results suggest that hybrid plasmonic structures (HPS) can play an even greater part as c-Si wafers become thinner.