Controlling available active sites of Pt-loaded TiO2 nanotube-imprinted Ti plates 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. An effective method for enhancing and controlling the active surface area of metal plates is provided in this study. The Ti plates are imprinted by TiO2 nanotubes (TNT) via the technique of anodization along with the ultrasonic vibration process. The available active area of imprinted Ti plates 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 plate as the CE substrate, while the cell with an imprint-free Ti plate 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 plate as the substrate with higher active surface area.