Bilayered photoanode from rutile TiO2 nanorods and hierarchical anatase TiO2 hollow spheres: a candidate for enhanced efficiency dye sensitized solar cells

Abstract

A bilayered photoanode for dye-sensitized solar cells (DSSCs) was constructed with the top layer using TiO₂ hierarchical hollow spheres (THS) and the second layer based on 3D TiO₂ nanorods. The anatase THS with diameters of 400–600 nm and with a specific surface area of 100.3 m² g⁻¹ were synthesized via a simple hydrothermal method. As a light scattering layer, the THS could provide dual-functions of adsorbing dye molecules and strong light-harvesting efficiency. The 3D TiO₂ nanorods consisting of 1D vertically aligned rutile TiO₂ nanorods (TNR) and 3D TiO₂ nanoflowers (TNF) were synthesized by a one-step hydrothermal method. The unique 3D nanostructure could offer a better light scattering capability, faster electron transport and lower electron recombination. Consequentially, the bilayered cell exhibited a much higher short-circuit photocurrent density of 15.60 mA cm⁻² and energy conversion efficiency of 7.50%, which indicated a 108.6% and a 36.8% increment of cell efficiency compared to the TNR-F electrode (7.36 mA cm⁻², 3.60%) and THS electrode (13.20 mA cm⁻², 5.48%), respectively.