Formation of spherical TiO2 nanorod aggregates with multiple functions for dye-sensitized solar cells

Spherical TiO2 nanorod aggregates were fabricated by a facile hydrothermal method and studied for exploring the formation mechanism and improving energy conversion efficiency in dye-sensitized solar cells (DSSCs). A four-step nucleation and growth process was proposed for the formation of the spherical TiO2 nanorod aggregates. Using the spherical TiO2 nanorod-aggregate photoelectrode for DSSC, an overall energy conversion efficiency of 6.05% and a short-circuit photocurrent density of 17.87 mA cm(-2) are achieved. These are respectively 46.1% and 44.9% higher than those of the DSSC using the nanoparticle photoelectrode. These improvements are attributed to the multiple functions of spherical TiO2 nanorod aggregates, including large surface area for sufficient dye adsorption, sub-micrometre size for efficient light scattering, open structure for quick electrolyte diffusion, and one-dimensional building units for longer electron lifetime. (C) 2012 Elsevier B. V. All rights reserved.