Cobalt-based electrolytes are highly tunable and have pushed the limits of dye-sensitized solar cells, enabling higher open-circuit voltages and new record efficiencies. However, the performance of these electrolytes and a range of other electrolytes suffer from slow electron transfer at platinum counter electrodes. High surface area platinum would enhance catalysis, but pure platinum structures are too expensive in practice. Here, a material-efficient host-guest architecture is developed that uses an ultrathin layer of platinum deposited upon an electrically conductive scaffold, niobium-doped tin oxide (NTO). This nanostructured composite enhances the counter electrode performance of dye-sensitized solar cells (DSCs) using a Co(II/III)BPY3 electrolyte with an increased fill factor and power conversion efficiency (11.26%), compared to analogous flat films. The modular strategy is elaborated by integrating a light scattering layer onto the counter electrode to reflect unabsorbed light back to the photoanode to improve the short-circuit current density and power conversion efficiency.