Green Preparation of TiO₂-ZnO Nanocomposite Photoanodes by Aqueous Electrophoretic Deposition

Aqueous-based electrophoretic deposition (EPD) of titania nanoparticles (Evonic's P25) was successfully applied to the fabrication of mesoporous electrodes for dye-sensitized solar cells (DSSC). Poor film adhesion and cracking arising from the electrolysis of water and interstitial water evaporation during drying were largely overcome via the selection of low EPD operating current density/DC voltage (0.1 mA cm −2 /2.5-3.1 V) but more importantly the addition of zinc nitrate in a 5 vol.% isopropanol-water suspension. As a result, a composite nanostructured TiO 2 -ZnO film was fabricated. Photoelectrochemical characterization indicates that in-situ formation of ZnO causes suppression of charge recombination at the electrode/electrolyte interface thus prolonging photoelectron lifetime. A 5.01% conversion efficiency was obtained under 1 sun illumination (100 mW·cm −2 ) of a 13 μm thick single transparent film. The efficiency was further improved to 6.19% upon further optimization via multi-layer construction of the transparent anatase film (18 μm thick) by repeated cycles of EPD.