Distance Dependence of Plasmon-Enhanced Photocurrent in Dye-Sensitized Solar Cells

We have fabricated titanium dioxide based dye-sensitized solar cells that incorporate corrosion-protected silver nanoparticles as plasmonic optical elements of the photoelectrode. The thickness of the TiO2 layer separating the dye from the nanoparticles has been systematically varied using atomic layer deposition. Over the range of TiO2 coating thicknesses examined (2 to 8 nm) there is clear enhancement of the dye extinction when plasmonic particles are present, with the enhancement increasing as the TiO2 thickness decreases. The optical enhancements translate into photocurrent enhancements, with the best cells (thinnest TiO2 coatings) showing 9-fold current enhancements under optimal monochromatic illumination. Preliminary experiments indicate that substantially larger optical enhancements are achievable with even thinner dye/particle separation layers, suggesting that even greater photocurrent enhancements may be achievable.