Immobilization of Silver Nanoparticles by Peptide Nucleic Acids in Surface Plasmon Enhanced Dye-Sensitized Solar Cells

Light absorption of dye molecules can be increased by the localized surface plasmons of silver nanoparticles (AgNPs), which can be used to enhance the photocurrent generation of dye-sensitized solar cells (DSSCs). Simultaneously, however, reverse electron transfer from the TiO2 working electrode to the I3−/I− electrolyte is also increased. In this work, peptide nucleic acid (PNA) was successfully used to immobilize AgNPs at different distances from the TiO2 layer and dye molecules. Together with results from previous studies, results here reveal that the optimal distance is between the lengths of possibly bent 2-nm alkane-thiols and 3.2- to 4.2-nm PNA. AgNPs immobilized by hybridization of PNA of this length lead to an increase in energy conversion efficiency from 3.1% to 4.0%. Furthermore, PNA forms π-electron stacks upon hybridization, which can reduce reverse electron transfer. With double-stranded PNA, the internal quantum efficiency of DSSCs could be increased more than 10%, from 73% to 88%, with 5.8- to 6.8-nm long double-stranded PNA.