Improved performance of flexible dye-sensitized solar cells based on hierarchical TiO₂ nanostructures with high surface area

One-dimensional TiO₂ nanostructures display remarkable performance in dye-sensitized solar cells by reducing the charge recombination; however, their relatively low surface area restricts both the dye absorption amount and solar energy conversion efficiency. Hydrothermal treatment of anodic TiO₂ nanotube arrays in 0.01 M (NH₄)₂TiF ₆ increased the surface area of TiO₂ photoanodes by generating hierarchical architecture. Hierarchical TiO₂ nanostructures obtained by optimal hydrothermal treatment conditions exhibited a wire-in-tube architecture decorated by nanoparticles on both the inner nanowire and the outer nanotube, which further increased the surface area. Flexible dye-sensitized solar cells based on these hierarchical nanostructures yield significantly improved solar energy conversion efficiencies due to enlarged surface area, increased dye loading, and superior light scattering capacity.