Plasmonic metal nanoparticles are known to work as light-harvesting antennae and to enhance photocurrents of photovoltaic cells and reaction rates of photocatalysts. The effects are expected to increase the energy conversion efficiency and to reduce the thickness of a light-absorbing layer and costs for materials. In this work, we examined the plasmonic enhancement of dye-sensitized photocurrents by Au nanoparticle ensembles with different particle densities to study the effects of interparticle plasmon coupling on the photocurrent enhancement. The coupling effects allow enhancement in a longer wavelength region. The optimum particle size for the enhancement by coupled nanoparticles is 100 nm, whereas that for isolated nanoparticles is 40 nm because the plasmon coupling effect is more significant for larger nanoparticles. Theoretical calculations reproduce those results.
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