Fabrication of dye-sensitized solar cells based on embedded photoelectrodes of TiO₂ nanotube-nanoparticles composite

We adopted an embedded photoelectrode, which consisted of a composite of TiO₂ nanotubes (NTs) and nanoparticles (NPs) in a Ti-foil substrate to improve the cell efficiency of conventional TiO₂ NP-based dye-sensitized solar cells (DSSCs) with Ti-foil substrates. The resulting increase in short-circuit current density (J_sc) of the embedded-TiO₂-NT-NP DSSCs was a major factor in the ∼30% improvement in cell efficiency compared to that of conventional TiO₂-NP DSSCs on Ti foil. In addition to more charge-transport pathways, the embedded-TiO₂-NT-NP DSSCs had a larger contact area between the TiO₂-NT-NP sidewall and the Ti foil, which reduced the electrical resistance and improved the charge-collection efficiency, resulting in the improvement in J_sc. The embedded-electrode DSSC with 11 μm TiO₂-NT and ∼8 μm TiO₂-NP layers exhibited the best efficiency of 5.8%, demonstrating that the embedded-electrode approach is an effective fabrication technique to improve the cell efficiency of the flexible DSSCs based on Ti-foil substrates.