Electrochemical Characterization of the UV-Photodegradation of Dye-Sensitized Solar Cells and usage in the Assessment of UV-Protection Measures

摘要

Within just 400 light hours exposure of UVA irradiation (X max 365 nm), glass mounted dye-sensitized solar cells with no UV filtration begin to fail drastically. The failure mode is shown to relate to electrolyte degradation rather than dye photo-bleaching and that this is directly related to TiO_2 photo-catalysis. The onset of failure is determined in less than 120 hours using electrochemical impedance data where the resistance of the electronic back reaction, between the TiO_2 semi-conductor and the electrolyte, drops markedly prior to the onset of degradation. At the point of complete cell failure this impedance value then dramatically increases as there is no longer an interfacial reaction possible between the TiO_2 and the degraded electrolyte. The degradation is most rapid for cells under electrical load indicating that the degradation of the electrolyte is related to hole production by direct excitation of the TiO_2.