Enhancement of PbS quantum dot-sensitized photocurrents using plasmonic gold nanoparticles.

For improvement of the conversion efficiency of solar cells, it is important to make effective use of near-infrared light, which accounts for about 40% of sunlight energy. Although solar cells based on quantum dots (QDs) such as PbS have been studied for the use of near-infrared light, their photoabsorption is not necessarily sufficient. In this study, we coupled PbS QD-sensitized solar cells with plasmonic Au nanoparticles (NPs) as light-harvesting antennae. As a result, the photocurrents of the cells were enhanced in the visible and near-infrared regions (500-1200 nm) due to interparticle plasmon coupling of spherical Au NPs. The maximum enhancement factor was 6. We also found that the optimum QD-NP spacing is shorter and that the maximum enhancement factor is higher when smaller QDs are used. These results suggest that a negative effect, quenching via energy transfer from QD to NP, is less significant for smaller PbS QDs.