Mechanism of degradation of electrolyte solutions for dye-sensitized solar cells under ultraviolet light irradiation

We studied the mechanism of the degradation of I−/I3−-containing electrolyte solutions for dye-sensitized solar cells under UV light irradiation. The yellow electrolyte solutions underwent achromatization during irradiation, indicating the reduction of I3−. We propose a mechanism involving the production of holes in TiO2, reaction of the holes with solvent molecules, and subsequent reduction of I3− by electrons remaining in the TiO2. Although the quantum yield of the photodegradation reaction is estimated to be low (3 × 10−3), this reaction can nevertheless be expected to affect the long-term stability of dye-sensitized solar cell devices.