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

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 (tau(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.