Improved performance of flexible dye-sensitized solar cells by introducing an interfacial layer on Ti substrates

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 TiO2 underlayer by hydrogen peroxide oxidation of Ti foil. This underlayer serves as a charge recombination barrier layer at the nanocrystalline TiO2/substrate interface, and suppresses the recombination reaction. This sponge-like TiO2 underlayer increases the electrical contact area between the Ti substrate and nanocrystalline TiO2, helping nanocrystalline TiO2 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 TiO2 underlayer increased the open-current voltage (V-OC) and fill factor (FF) due to prolonged electron life time (tau(eff)), and minimized resistance at the TiO2/Ti interface (R-CT). With an optimal thickness of nanocrystalline TiO2 and concentration of I-2, we achieved a conversion efficiency of 6.75% for a back-illuminated DSSC.