Anodic Deposition of Ultrathin TiO2 Film with Blocking Layer and Anchoring Layer for Dye-Sensitized Solar Cells

Abstract

Ultrathin anatase TiO2 films were coated on the fluorine-doped tin oxide (FTO) glass by anodic electrodeposition followed by annealing at 450°C before the formation of thick TiO2 layer. The electrodeposited TiO2 films were more compact structure near the FTO surface (inner layer), and became less compact further away from the surface (outer layer). The outer layer of film deposited at 10 μA cm−2 was composed of granular nanoparticles and that of film deposited at 5 μA cm−2 was composed of short nanorods. The inner compact layer could act as a blocking layer to suppress the charge recombination. The outer loose layer could provide an anchoring layer for a better electrical contact between FTO and thick TiO2 layer. The photoelectron conversion efficiency (η) of dye-sensitized solar cell (DSC) using TiO2-coated FTO deposited at 10 μA cm−2 was 6.9%, which is higher than that of DSC using bare FTO (6.5%). The outer anchoring layer composed of short nanorods deposited at 5 μA cm−2 could significantly reduce the interfacial contact resistance between FTO and main TiO2 layer. Therefore, η of DSC was further increased to 7.1% after employing the TiO2-coated FTO deposited at 5 μA cm−2.