Faster dye-adsorption of dye-sensitized solar cells by applying an electric field

In the conventional dye-adsorption process of dye-sensitized solar cells (DSCs), the FTO/TiO₂ photo electrode is soaked in the dye solution, allowing dye molecules to be adsorbed onto the TiO₂ surface by covalent bonds between dye molecules and TiO₂ particles. This process requires a very long time, ranging from several hours to several days. Therefore, it is necessary to take other steps for faster dye-adsorption. We propose that more dye molecules will be adsorbed onto the TiO₂ surface during the early period of the dye-adsorption process if ionized dye molecules are accelerated toward the TiO₂ layer. To achieve ionization, an electric field was applied above and below the soaked photo electrode to accelerate the dye molecules, which resulted in faster dye-adsorption. To determine if faster dye-adsorption was caused by the electric field during the dye-adsorption process, the effect in terms of photovoltaic performance, the adsorption temperature, and the absorbance spectra were examined. The result showed that DSCs with an electric field applied during the dye-adsorption process reached the maximum current in 5 h, while conventional DSCs required 12 h. Furthermore, this effect was confirmed by reversing the electric field which produced a cell with worse performance compared to a conventional cell.