Au/TiO2 nanotube array based multi-hierarchical architecture for highly efficient dye-sensitized solar cells

Abstract Control over balanced high light-harvesting and efficient charge transport is of crucial importance for photoelectrochemical applications but still remains great challenge. We develop here single-wall TiO2 nanotube array with in-situ deposited Au nanoparticles. Based on this Au–TiO2 hybrid, we further build a “cigar-like” Au/TiO2-nanotube-array/TiO2-nanoparticles multi-hierarchical architecture through a novel vacuum-assisted colloid-filling approach for dye-sensitized solar cell application. In this elaborate structure, Au nanoparticles welding on nanotube walls play dual roles of direct injecting hot electrons into TiO2 to elevate the conductivity of TiO2 film by about 4 times (under illumination) for fast electron transport, and introducing a plasmonic effect to improve light-harvesting as well. Meanwhile, the thick TiO2 nanoparticulate decoration provides the photoanode vast surface area for ~3.2 times the dye-loading amount of the pristine TiO2 nanotube array based electrode, which will further boost the light-harvesting remarkably. The resulting dye-sensitized solar cell yields an impressively high power conversion efficiency of 8.93%, which is 190.4% that of the pristine TiO2 nanotube array based device. The technology presented in this work provides also a promising prospect for the preparation of multi-hierarchical structures for a wide range of applications, such as photocatalysis and gas sensors.