Abstract
Titania is one of the key materials used in 1D, 2D, and 3D nanostructures as electron transport media in energy conversion devices. In the present study, it is shown that the electronic properties of TiO2 nanotubes can be drastically improved by inducing a nanotwinned grain structure in the nanotube wall. This structure can be exclusively induced for "single-walled" nanotubes with a high-temperature treatment in pure oxygen atmospheres. Nanotubes with a twinned grain structure within the tube wall show a strongly enhanced conductivity and photogenerated charge transport compared to classic nanotubes. This remarkable improvement is exemplified in the electronic properties by using nanotwinned TiO2 nanotubes in dye-sensitized solar cells where a significant increase in efficiency of up to 10.2% is achieved.