High rate reactive sputter deposition of TiO2 films for photocatalyst and dye-sensitized solar cells

We fabricated dye-sensitized solar cells (DSCs) using TiO2 films deposited on various substrates by reactive magnetron sputtering with midfrequency pulsing and process control units, and evaluated their performance. Two pulse modes, i.e., unipolar pulse and pulse packet modes, were utilized to deposit TiO2. The highest conversion efficiency achieved was 3.7% when 10-mu m-thick TiO2 films were deposited on glass substrates coated with fluorine-doped tin oxide (FTO) using the unipolar pulse mode in the oxide mode and postannealing in air. On the other hand, the conversion efficiency achieved was 2.7% for cells with 10-mu m-thick TiO2 films deposited on glass substrates coated with FTO using the pulse packet mode without postannealing, and it dropped to 1.3% when the unipolar pulse mode was used. The relationships between the photocatalytic decomposition activity and the DSC characteristics with regard to the TiO2 films were investigated in detail. The reduction in the density of defects in the TiO2 films led to an improvement in both the photocatalytic activity and the DSC characteristics.