Synthesis of {010}-faceted anatase TiO2 nanoparticles from layered titanate for dye-sensitized solar cells

Abstract

Crystal facets exposed on TiO₂ nanoparticles strongly affect dye molecule adsorption and cell performance in dye-sensitized solar cells (DSSCs). In this study, size- and morphology-controllable {010}-faceted anatase-type TiO₂ nanocrystals, including rhombic, tetragonal, and leaflike nanocrystals and platelike mesocrystals, were synthesized via hydrothermal treatment of layered titanate (HTO) nanosheet colloidal solutions. The formation reactions and nanostructures of the anatase nanocrystals were investigated using XRD, FE-SEM, and TEM. There are two kinds of reactions in the formation process of the anatase nanocrystals from the HTO nanosheets. One is an in situ topotactic structural transformation reaction and another is a dissolution–deposition reaction. The DSSC performance of the {010}-faceted anatase nanocrystals was investigated by measurements of I–V characteristics, electrochemical impedance spectra, and dye adsorptions and compared with [111]-faceted P25 nanocrystals and spherical ST20 nanocrystals without a specific facet on the surface. The DSSC results suggested that the J_sc and η values increase in the order of spherical nanocrystals without a specific facet < [111]-faceted nanocrystals < {010}-faceted nanocrystals, which concludes that the facet on the nanoparticle surface significantly impacts on the DSSC performance and the {010}-faceted nanocrystals are promising for the high-performance DSSCs.