Size-tunable mesoporous spherical TiO2as a scattering overlayer in high-performance dye-sensitized solar cellsElectronic supplementary information (ESI) available: Schematic on “dilute mixing”-driven hydrolysis is shown. Also, synthetic procedure and physical properties of pore size-controlled MS TiO2are summarized. See DOI: 10.1039/c1jm11043h

Size-tunable mesoporous spherical TiO2(MS TiO2) with a surface area of ∼110 m2g−1have been prepared through combination of “dilute mixing”-driven hydrolysis of titanium(iv) tetraethoxide and solvothermal treatment. The hierarchically structured MS TiO2are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and nitrogen sorption analysis. Using three different MS TiO2(587, 757, and 1554 nm in diameter) as a scattering overlayer on a transparent nanocrystalline TiO2film, bi-layered dye-sensitized solar cells (DSCs) have been fabricated. Since the MS TiO2particles are comprised of ∼10 nm nanocrystallites that cluster together to form large secondary spheres, they can function as light scatterers without sacrificing the surface area for dye-uptake. As a result, the present MS TiO2-based cells perform a noticeable improvement in the overall efficiency: maximum 9.37% versus6.80% for the reference cell made of a TiO2nanocrystalline film. This extraordinary result is attributed to the dual effects of enhanced dye loading and light scattering. [ABSTRACT FROM AUTHOR]