Tri-functional hierarchical TiO2 spheres consisting of anatase nanorods and nanoparticles for high efficiency dye-sensitized solar cells

Hierarchical anatase TiO2 spheres consisting of nanorods and nanoparticles are successfully prepared via a simple acid thermal method using titanium n-butoxide and acetic acid, which will overcome the kinetic and light-scattering limitations of nanoparticles and the surface area limitations of one-dimensional nanostructures, as photoelectrodes for dye-sensitized solar cells. The as-prepared and calcined hierarchical spheres were characterized by transmission electron microscopy, scanning electron microscopy and X-ray powder diffraction. The DSSC based on hierarchical TiO2 spheres as the photoelectrode shows a highly efficient power conversion efficiency (10.34%) accompanied by 18.78 mA cm−2 in short-circuit photocurrent density and 826 mV in open-circuit voltage. The great improvements of photocurrent density and power conversion efficiency for hierarchical TiO2 spheres compared to P25 nanoparticle photoelectrodes are mainly attributed to a considerable surface area, a higher light scattering ability, and faster electron transport rates and slower recombination rates for the former.