Effects of water intrusion on the charge-carrier dynamics, performance, and stability of dye-sensitized solar cells

We report on the influence of water on the charge-carrier dynamics, photocurrent density-photovoltage (J-V) properties, and stability of dye-sensitized TiO2 solar cells (DSSCs) containing two different commonly used solvents. Adding water to the solvents was found to strongly alter the energy level alignments, retard recombination at the electrode-redox electrolyte interfaces, and increase the dark exchange current density. The added water had no effect on electron transport, however. The addition of water to the cells increased the photocurrent densities, photovoltages, and solar cell efficiencies but lowered the fill factors. Changes in the J-V characteristics were shown to result from the effects of water on the energetics and kinetics of transport and recombination in the DSSCs. Regardless of the solvent used in the DSSCs, the added water had no observed effect on the cell stability during 1000 h of continuous illumination under full sunlight (AM1.5).