Effect of TiO2 nanotubes lateral spacing on photovoltaic properties of dye-sensitized solar cells

Vertically aligned TiO₂ nanotube arrays (~8 μm long, ~110 nm wide) have been fabricated through anodic oxidation of Ti-metal sheet in fluoride-containing electrolyte. By changing the volume ratio of ethylene glycol and diethylene glycol in the electrolyte, TiO₂ nanotube arrays with different tube-to-tube lateral spacing, i.e., closely packed, just separated, and fully separated, have been synthesized and applied as photoanodes for dye-sensitized solar cells (DSSCs). Photovoltaic efficiency of 2.99 %, 3.34 %, and 3.44 % has been obtained for DSSCs based on the closely packed, just separated, and fully separated TiO₂ nanotube arrays, respectively, illustrating the effect of tube-to-tube lateral spacing of TiO₂ nanotube arrays on the performances of DSSCs. It is suggested that fully separated TiO₂ nanotube arrays are beneficial to the conversion efficiency of DSSCs due to higher dye loading and faster electron transfer.