A hierarchical homogeneous core–shell structure of TiO2 hollow microspheres for high efficiency dye-sensitized solar cells

Core–shell TiO 2 (cs-TiO 2 ) hollow microspheres are prepared via a facile hydrothermal method, by using titanium potassium oxalate precursor in dilute sulfuric acid. The characterization shows that the as-prepared TiO 2 microspheres have core–shell structure. The diameters of cs-TiO 2 microspheres are in the range of 2–5   μm. The optical investigation evidences that the cs-TiO 2 microsphere film exhibits a prominent light-scattering effect at a wavelength range of 600–800   nm. The cs-TiO 2 microspheres are applied as a scattering layer on top of a nanocrystalline P25 film, serving as the photoanode of dye-sensitized solar cells (DSSCs). A high efficiency of 7.7% is achieved after introducing the cs-TiO 2 hollow microsphere scattering layer, compared with 6.21% for the photoanode with commercial P25. Based on the optical investigation and electrochemical impedance measurement, the improved efficiency can be ascribed to the enhanced light-scattering ability and the reduced interface recombination rate.