Hierarchically macro–mesoporous TiO2 film via self-assembled strategy for enhanced efficiency of dye sensitized solar cells

Abstract

The hierarchically porous structure of TiO2 film plays an important role on improved photoelectric conversion efficiency in dye-sensitized solar cells (DSSCs). It is highly required to develop a facile strategy to prepare the hierarchical porous photoelectrode. In this study, a novel hierarchically macro–mesoporous TiO2 film as photoelectrode of DSSCs is fabricated by a self-assembled process of TiO2 nanoparticles via TiF4 hydrolysis. The hydrolysis of TiF4 is accompanied with self-assembled process of TiO2 nanoparticles on the surface of electrophoretic-deposited titanate nanotube film which provides effective active sites for the deposition of TiO2 nanoparticles owing to a large amount of hydroxyl groups, resulting in the formation of hierarchically porous structures. The hierarchically porous TiO2 film is mainly composed of mesopores with a size of 2–50nm and macropores with a wide range of 0.5–5μm, which contribute to an obviously higher conversion performance (6.70%) than nonporous P25-TiO2 film (4.01%). The main reasons for enhanced conversion efficiency of hierarchically porous TiO2 film can be attributed to adsorption of more dye molecules, rapid diffusion and efficient transport of electrolyte, and longer electron lifetime. This work may provide new insights into preparing porous structure of TiO2 films in DSSCs for modification of photoelectric conversion efficiency.