Influence of a TiCl₄Post-Treatment on Nanocrystalline TiO₂Films in Dye-Sensitized Solar Cells

Abstract

In this study, the influence of the TiCl(4) post-treatment on nanocrystalline TiO(2) films as electrodes in dye-sensitized solar cells is investigated and compared to nontreated films. As a result of this post-treatment cell efficiencies are improved, due to higher photocurrents. On a microscopic scale TiO(2) particle growth on the order of 1 nm is observed. Despite a corresponding decrease of BET surface area, more dye is adsorbed onto the oxide surface. Although it seems trivial to match this finding with the improved photocurrent, this performance improvement cannot be attributed to higher dye adsorption only. This follows from comparison between incident photon to current conversion efficiency (IPCE) and light absorption characteristics. Since the charge transport properties of the TiO(2) films are already more than sufficient without treatment, the increase in short circuit current density J(SC) cannot be related to improvements in charge transport either. Transient photocurrent measurements indicate a shift in the conduction band edge of the TiO(2) upon TiCl(4) treatment. It is concluded that the main contribution to enhanced current originates from this shift in conduction band edge, resulting in improved charge injection into the TiO(2).

Optimization of nanostructured titania photoanodes for dye-sensitized solar cells: Study and experimentation of TiCl4 treatment

“…As widely accepted, some of the effects of TiCl 4 post-treatment are a decrease in the BET (Brunauer Emmett Teller) surface area and an increase in the particle diameter and mass of the treated TiO 2 film [20]. We experimentally verified that TiCl 4 treatment produced an increase in the TiO 2 particle diameter (Fig.…”

“…1), a significant film mass (35%) and no modification in the layer thickness profile. This is explained by a decrease in the BET surface area; it is possible that the TiCl 4 removes specific surface states that serve to quench the dye excited state, improving the binding of the dye on the TiO 2 film and reducing the fraction of the TiO 2 film inaccessible for the dye [13,20].…”

“…The TiCl 4 treatment on TiO 2 film produces a downward shift in the conduction band [20] and consequently results in enhancing the electron injection efficiency. This is the main cause of the upward shift in the photo-injected current (Fig.…”

Energy and Hole Transfer between Dyes Attached to Titania in Cosensitized Dye-Sensitized Solar Cells

“…32 Figure 2A shows the optical density (OD) versus wavelength during different stages of cosensitization. The titania films were first dipped in a 0.1 mM AS02 solution in DMF for 15 min, then rinsed in DMF and dried with N 2 (green line).…”

Improving the efficiency of dye-sensitized solar cells by photoanode surface modifications

“…In that study, TiCl4 surface treatment was used to improve the performance of relatively impure Degussa P25 TiO2 NPs. Sommeling et al [45] studied the influence of TiCl4 post-treatment on nanocrystalline TiO2 photoanodes. As a result of this post-treatment, cell efficiencies were improved due to higher photocurrents.…”