Here, we report plasmonically enhanced thin dye-sensitized solar cells (DSSCs) in an imidazolium-dicyanamide based ionic liquid, in which size-controlled metal (silver) nanoparticles (AgNPs) with passivation layers of a few nanometers are arranged into the electrolyte and photo-electrodes. It was revealed that the AgNPs in the electrolyte and the photo-electrode have distinct effects on device performance via different coupling mechanisms. Strong far-field scattering is critical in the electrolyte while near-field scattering is efficient in the photo-electrode. Indeed, we find that the power conversion efficiency of the DSSC can be substantially improved by a synergistic arrangement of the AgNPs in the electrolyte and the photo-electrode. Furthermore, an imidazolium-dicyanamide based nonvolatile ionic liquid electrolyte for MNPs is demonstrated to provide thin plasmonic DSSCs with good stability.