Controlling Active Surface Area of TiO2 Nanotube Imprinted Ti Foils for Efficient Dye-Sensitized Solar Cells

The counter electrode (CE) of dye–sensitized solar cells (DSSCs) plays an important role for transferring electrons and catalyzing the I⁻/I₃⁻ reduction. Active surface area of the substrate determines the reduction sites of the deposited catalyst as well as the catalytic ability of the CE. A simple and effective method for enhancing and controlling the active surface area of metal foils is provided in this study. The Ti foils are imprinted by TiO₂ nanotubes (TNT) via anodization and ultrasonic vibration techniques. The active surface area of imprinted Ti foils is controlled by varying the anodization voltage to produce TNT imprints with different diameters and depths. A solar–to–electricity conversion efficiency (η) of 9.35% was obtained for the DSSC with a TNT–imprinted Ti foil as the CE substrate, while the cell with an imprints–free Ti foil shows an η of 7.81%. The enhanced η is due to the improved electrocatalytic ability of the CE by using the TNT–imprinted Ti foil as the substrate with higher active surface area.