Highly ordered TiO2 nanorod arrays (NRAs) were directly grown on an F:SnO2 (FTO) substrate without any seed layer by hydrothermal route. For a larger surface area, the second-step hydrothermal treatment in hydrochloric acid was carried out to the as-prepared TiO2 NRAs. The results showed that the center portion of the TiO2 nanorods were dissolved in the etching solution to form a nanocave at the initial etching process. As the etching time extended, the tip parts of the nanocave wall split into lots of nanowires with a reduced diameter, giving rise to a remarkable increase of specific surface area for the TiO2 NRAs. The TiO2 films after etching treatment were sensitized by CdS quantum dots (QDs) to fabricate quantum dot-sensitized solar cells (QDSSCs), which exhibited a significant improvement in the photocurrent density in comparison with that of the un-treated device, this mainly attributed to the enhancement of QD loading and diffused reflectance ability. Through modifying the etching TiO2 films with TiCl4, a relatively high power conversion efficiency (PCE) of 3.14 % was obtained after optimizing the etching time.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-016-1236-9) contains supplementary material, which is available to authorized users.

Highly ordered TiO2 nanorods are considered promising for photoanodes in dyesensitized solar cells due to their high charge transfer rate of photo-generated electrons, but they often suffer from low specific area, which may lead to a low conversion efficiency. Here, we produce long vertical single-crystalline rutile TiO2-nanorod arrays on FTO by the hydrothermal method. To further increase the specific area, the TiO2nanorod arrays are etched in a secondary hydrothermal process by hydrochloric acid. The etching time have a major effect on the nanorod microstructure and on the dye-sensitized solar cells efficiency. The best result is reached with 8 hours of etching, which resulted in a record high conversion efficiency of 11.14  0.12 % (certified efficiency 10.3%) under AM 1.5 conditions. The record cell has an open voltage of 0.79 V and a short current density of 21.59 mA/cm 2 . The proposed manufacturing approach of TiO2 nanorods is 2 highly potential for producing high-efficiency dye-sensitized solar cells.

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TiO2 films with 1D/3D network structures have been prepared via two-step hydrothermal method and applied in DSSCs, an high efficiency of 7.68% was achieved.