Sea urchin-like TiO2 microspheres as scattering layer of nanosized TiO2 film-based dye-sensitized solar cell with enhanced conversion efficiency

Abstract Sea urchin-like TiO 2 microspheres are synthesized through a facile one-step solvothermal process by using titanium tetrabutoxide (TBOT) as titanium source. The obtained TiO 2 microspheres with ∼3 μm diameter display anatase phase and hierarchical structures composed of TiO 2 nanoribbons containing secondary nanoparticles with an average particle size of ∼15 nm. By using as photoanode material, the anatase TiO 2 microspheres film-based dye-sensitized solar cells (DSSCs) show higher short-circuit current but slightly lower conversion efficiency than the TiO 2 nanoparticles (P25) film-based one; while the bilayer film-based solar cell by using the TiO 2 microspheres as overlayer of the P25 film exhibits significantly improved photovoltaic performance with an efficiency up to 7.14%, improved by 26.6% as compared to the P25 film-based one (5.64%). The anatase TiO 2 microspheres as overlayer can not only enhance the light harvesting capability due to their scattering effect of the sea urchin-like hierarchical structures, but also contribute to the larger dye-loading amount, which lead to a decrease in the charge transfer resistance, charge recombination and dark current, and then resulting in the improved photovoltage and photovoltaic performance. The simple fabrication method of the bilayer solar cell, which contains a photoanode composed of P25 film as underlayer and sea urchin-like TiO 2 hierarchical microspheres as overlayer, demonstrates a strategy for the development of the low cost and high efficiency solar cells through tuning the photoanode's component and structure.