Preparation of brookite titania quasi nanocubes and their application in dye-sensitized solar cells

Abstract

Brookite TiO₂ quasi nanocubes with high phase purity and thermal stability were synthesized through a hydrothermal process. The obtained brookite TiO₂ quasi nanocubes have a mean size of ∼50 nm with a specific surface area of ∼34.2 m² g⁻¹. When used as a photoanode material, the single brookite TiO₂ nanocubes film-based dye-sensitized solar cell (DSSCs) shows higher open-circuit voltage but lower conversion efficiency than the single nanosized anatase TiO₂ film-based one with a similar film thickness; while using the brookite TiO₂ nanocubes as an overlayer of the nanosized anatase TiO₂ film, the fabricated bilayer solar cells exhibit significant enhancement in both the open-circuit voltage and short-circuit current. In addition, the corresponding bilayer solar cell with an optimized overlayer thickness gives a conversion efficiency up to 8.83% with a 23.8% improvement when compared to the single anatase cell (7.13%). The brookite nanocubes used as an overlayer not only reduce the charge recombination and dark current, but also prolong the electron lifetime, which leads to an enhanced voltage and photocurrent, and therefore the improved photovoltaic performance of the bilayer solar cell. These results demonstrate the simple fabrication method used to prepare brookite TiO₂ nanocubes and their application as an overlayer are promising and offer a strategy for the development of low-cost and high efficiency DSSCs through tuning the photoanode's components and structure.