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

• Core–shell TiO2 microspheres are prepared via a facile hydrothermal method.
• Core–shell TiO2 microspheres have a prominent light-scattering property.
• The DSSC using core–shell TiO2 microspheres as scattering layer achieves an efficiency of 7.7%.

Core–shell TiO2 (cs-TiO2) 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 TiO2 microspheres have core–shell structure. The diameters of cs-TiO2 microspheres are in the range of 2–5 μm. The optical investigation evidences that the cs-TiO2 microsphere film exhibits a prominent light-scattering effect at a wavelength range of 600–800 nm. The cs-TiO2 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-TiO2 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.

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