Atomic Layer Deposition of Ta-doped TiO2 Electrodes for Dye-Sensitized Solar Cells

Ta-doped TiO 2 inverse opals were obtained by selective etching of a silica template after atomic layer deposition (ALD) of Ta-doped TiO 2 films and were applied as an electrode for dye-sensitized solar cells (DSSCs). Ta content in the Ta-doped TiO 2 film was controlled by the Ta/(Ta+Ti) unitcycle ratios in the Ta–TiO 2 supercycle of ALD. Also, excellent step coverage of nearly 100% in the inverse opal structure was confirmed by field-emission scanning electron microscopy (FE-SEM). Maximum photoconversion efficiency of 1.56% was achieved with the Ta (3.4 atom %)-doped TiO 2 inverse opal electrode due to increased photocurrent density. However, further Ta doping (> 4.9 atom %) decreased the J sc and photoconversion efficiency.