Preparation of nanocrystalline ZnO/TiO₂ film and its application to dye-sensitized solar cells

Dye-sensitized solar cells (DSSCs) were built by using ZnO/TiO₂ films as electrodes consisting of ZnO nanorod arrays coated with TiO₂ nanoparticles (NPs) in sol or slurry form prepared by solgel methods. The addition of TiO₂ sol to ZnO arrays resulted in an improvement of cell performance, but the cell efficiency was not high. The cell efficiency was more improved by coating of ZnO arrays with TiO₂ slurry. The tetraethylammonium hydroxide surfactant was effective to control TiO₂ NPs suspension between sol and slurry. The penetration of TiO₂ sol or slurry into ZnO array was important, especially in the long nanorod array. The cell performance of ZnO/TiO₂ electrode increased more by TiO ₂ slurry than by TiO₂ sol because TiO₂ sol shrank more during calcination.