Monodisperse TiO2 hierarchical hollow spheres assembled by nanospindles for dye-sensitized solar cells

Monodisperse TiO2 hollow spheres assembled by nanospindles were prepared via the facile hydrothermal reaction of peroxotitanium complex precursors. Time dependent trails revealed that the shape evolution involved a one-step chemical conversion from amorphous Ti complex microspheres to anatase TiO2 hierarchical hollow spheres. Meanwhile, the sizes of the spheres could be tuned in a region of 400-1000 nm by simply adjusting the ammonia dosage of the precursor solution. Furthermore, these as-prepared hollow spheres were deposited as a scattering layer on top of the TiO2 nanocrystalline film, and a high energy conversion efficiency of 8.10% was demonstrated based on the bilayer photoanode, in contrast to a 7.29% conversion efficiency for the cell with a pure nanocrystalline photoanode.