Influence of Annealing Ambient on the Photoelectric and Photoelectrochemical Properties of TiO2 Nanorod Arrays

Ordered TiO2 nanorod arrays (NRAs) have been synthesized on transparent conducting F-doped SnO2 (FTO) substrates via a facile hydrothermal method for dye-sensitized solar cells (DSSCs). Annealing in air at 500°C resulted in a large enhancement of DSSC performance, while the performance was much decreased after annealing in the reducing ambient (Ar or vacuum). This was ascribed to a lowering of the interfacial charge separation or injection. Moreover, it was also found that the photoelectrochemical activity of TiO2 NRA was enhanced after annealing in Ar or vacuum, which was totally opposite to the variation of DSSC performance, and was ascribed to the enhancements of both interface charge transfer and visible-light absorption (as had been confirmed by the color change).