The effect of TiCl4 treatment on the performance of dye-sensitized solar cells.

Titanium dioxide (TiO2) is used to form the anode in dye sensitized solar cells (DSSCs) and is thus one of the crucial components of this type of solar cell. A large range of treatments of the titania anode before deposition of the dye have been applied to improve the performance of DSSCs among which the TiCl4 treatment is the most frequently used treatment. The present study investigates how the TiCl4 treatment of the TiO2 changes the anode. For this purpose, different sample sets, nontreated, post-treated, and pre-post treated cells, were fabricated and analyzed with electron and ion scattering spectroscopy to investigate how they change the titania surface and consequently influence the cell performance. After the TiCl4 treatment, the short circuit current density (Jsc), open-circuit voltage (Voc), and efficiency significantly improved. An upward shift in the conduction band of the semiconductor as an effect of TiCl4 treatment was measured using inverse photoemission spectroscopy and UV-photoelectron spectroscopy. An increase in dye adsorption due to the treatment was found through neutral impact collision ion scattering spectroscopy measurement. The change in the energy level alignment of the titania and the adsorbed dye and the increase in dye loading explain the threefold increase of power conversion of the cells.