Studies on the efficiency enhancement of co-sensitized, transparent DSSCs by employment of core-shell-shell gold nanorods

In this article, we present studies concerning the efficiency enhancement of dye-sensitized solar cells (DSSC) containing cocktails of organic donor-?-acceptor (D-?-A) dyes (L0 and L1) and a squaraine sensitizer (SQ2) by means of the localized surface plasmon resonance (LSPR) effect induced by gold nanorods (GNRs) embedded within the semiconductor layer. In view of the potential application of DSSC devices for building integration, dye cocktails were selected to maximize transparency in the 500-600 nm region, where human eye sensitivity has its peak. Thus, the chosen organic dyes and the squaraine sensitizer had absorption maxima in the 380-410 nm region and above 660 nm, respectively. Thanks to their specific asymmetry, GNRs with a 3:1 aspect ratio could enhance organic dye absorption due to their transverse resonance component as well as squaraine absorption in the far-red/near-infrared (NIR) spectral range due to their longitudinal resonance component; furthermore, they were sequentially coated with thin layers of SiO2 and TiO2 in order to make them robust enough to withstand thermal film sintering and minimize charge recombination during the photovoltaic operation. Whereas incorporation of GNRs in the photoanode did not improve the efficiency of cells prepared with the L0/SQ2 dye combination, a significant increase of 23% (from 3.50% to 4.32%), comparable to that observed for Ru-sensitizer N719, was observed in the case of the L1/SQ2 dye cocktail.