Specific interaction between dyes and ions in dye -sensitized solar cells observed with temporal spectral shift of dyes

Long-lived bleach responses with a lifetime of several milliseconds were found for the ruthenium and organic dyes in dye-sensitized solar cells. These responses were caused by the specific interaction between each dye and ionic species in the electrolyte. For the ruthenium and D131 dyes, iodide ions were necessary for the shift, while lithium cations induced it for D149, even though the molecular structure is quite similar for D131 and D149. The bleach peak was caused by the blue shift of the absorption peak even after the regeneration of the dye from the dye cation, which would be induced by the composition/concentration change of the ionic species on the electrolyte side due to the redox reactions or charge compensation. The result was confirmed by the dependence of the transient absorption spectra on the, order from microsecond to millisecond on various anion and cation conditions, dye structures, and redox species. (C) 2016 Elsevier B.V. All rights reserved.