The effects of water content on the degradation behavior of dye-sensitized solar cells were studied by adding water isotopes (H(2)O, D(2)O, and H(2)(18)O) to the electrolytes. Time-dependent photovoltaic performance of the water-added DSSCs was monitored accompanied with the diffuse-reflectance infrared Fourier transform (DRIFT) technique and electrochemical impedance spectroscopy (EIS) measurement. DRIFT technique was utilized to study the chemical reactions that occurred on the working electrodes (TiO(2)). EIS was implemented to evaluate the effects of the charge-transfer resistance at the interfaces between TiO(2)/dye/electrolyte. Results show that the degradation rates of the cells in presence of water isotopes were in the order of H(2)O> D(2)O> H(2)(18)O. In addition, the values of open-circuit voltage (V(oc)) and fill factor (FF) for the water-added cells increased within first 12 h sun irradiation. However, their short-circuit current (J(sc)) and efficiency (eta) decreased during the sun irradiation. Moreover, a new peak assigned to LiNCS was noticed after soaking in water-added electrolytes for 48 h, attributing to the interaction of lithium ions with free thiocyanate ions from the dye. (C) 2011 Elsevier B.V. All rights reserved.