Influence of Sodium Cations of N3 Dye on the Photovoltaic Performance and Stability of Dye‐Sensitized Solar Cells

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Abstract
Little things count: The number of protons and the nature of cations of the dye influence the open‐circuit potential and the short circuit current of dye‐sensitized solar cells (DSCs, see picture). Thus, the effect of substituting the two tetrabutylammonium counter ions in the standard N719 dye by sodium ions allows the improvement on the performance and stability of DSCs. We report on the effect of substituting the two tetrabutyl ammonium counter ions of the standard N719 dye by sodium ions on the performance and stability of dye‐sensitized solar cells (DSCs). The disodium analogue of N719 in conjunction with a non‐volatile electrolyte gives a conversion efficiency of 7.6 % under standard global AM 1.5 sunlight. Devices maintain 99 % of their initial performance after 1000 h under full sunlight aging at 50 °C. Electrochemical impedance spectroscopy and photovoltage transient decay studies reveal the evolution of the solar cell parameters during aging. Remarkably, upon aging a decrease in the rate of electron back reaction with the triiodide ions across the TiO2/electrolyte interface appears as well as enhanced electronic conduction in the TiO2 film.