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

Vertically aligned TiO2 nanotube arrays (similar to 8 mu m long, similar to 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.