Abstract: A corrosion-free electrolyte for use in plasmonic-enhanced dye-sensitized solar cells includes ions of a plasmon-supporting metal, in particular iodide anions of the plasmon-supporting metal especially, but not exclusively, gold(I) diiodide anions ([AuI2]?) and/or gold(III) tetraiodide anions ([AuI4]?). Methods for preparing the electrolyte are also disclosed, as are methods for reducing the corrosion of plasmonic structures in plasmonic-enhanced dye-sensitized solar cells and for improving the efficiency of dye-sensitized solar cells, in particular plasmonic-enhanced dye-sensitized solar cells, by disposing the electrolyte between the electrodes.