Rice-like brookite titania as an efficient scattering layer for nanosized anatase titania film-based dye-sensitized solar cells

• Rice-like brookite TiO2 with high purity were prepared via hydrothermal method.
• The brookite particles were used as overlayer of nanosized anatase TiO2 photoanode.
• Bilayer TiO2 film-based DSSCs were fabricated by using the above photoanode.
• Brookite overlayer enhances VOC of DSSCs fabricated with anatase TiO2 photoanode.
• Bilayer DSSC's efficiency is improved by 29% as compared to the anatase-based one.

Rice-like brookite TiO2 particles with high phase purity and ∼600 nm particle diameter were synthesized through a hydrothermal method, and then bilayer TiO2 film-based dye-sensitized solar cells (DSSCs) were fabricated by using photoanode consisting of nanosized anatase TiO2 film as underlayer and the above brookite TiO2 submicrometer particle film as overlayer. The effects of the brookite overlayer on the light scattering and photoelectrochemical performances of the anatase TiO2 film-based DSSCs were investigated by using UV–vis diffused reflectance absorption spectra (DRS), open-circuit voltage decay (OCVD) curves and electrochemical impedance spectra (EIS) measurements. It is found that the bilayer film-based DSSCs have much better light harvesting capability, higher open-circuit voltage and longer electron lifetimes than the single anatase TiO2 film-based one. After optimizing the thicknesses of underlayer and overlayer, the corresponding bilayer TiO2 film-based DSSC gives conversion efficiency up to 8.83%, with a 29% improvement in the efficiency as compared to that (6.82%) of the single film-based one under AM 1.5G one sun irradiation. The present results represent a clear advance towards efficient light scattering materials for the nanosized TiO2 film-based solar cells with low-cost and high efficiency.

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