Abstract
The recombination reaction of injected electrons with triiodide ion in the electrolyte limits the efficiency of dye-sensitized solar cells (DSSCs). This study reports the preparation of a sponge-like and conformal TiO 2 underlayer by hydrogen peroxide oxidation of Ti foil. This underlayer serves as a charge recombination barrier layer at the nanocrystalline TiO 2 /substrate interface, and suppresses the recombination reaction. This sponge-like TiO 2 underlayer increases the electrical contact area between the Ti substrate and nanocrystalline TiO 2 , helping nanocrystalline TiO 2 attach to the Ti substrate. This study compares the performance of DSSCs that were subjected to different Ti surface treatments. Electrochemical impedance spectroscopy results confirm that the proposed sponge-like TiO 2 underlayer increased the open-current voltage (V OC ) and fill factor (FF) due to prolonged electron life time (τ eff ), and minimized resistance at the TiO 2 /Ti interface (R CT ). With an optimal thickness of nanocrystalline TiO 2 and concentration of I 2 , we achieved a conversion efficiency of 6.75% for a back-illuminated DSSC. © The Royal Society of Chemistry 2011.