The different electron transport of two nanotubes incorporated in working electrode of dye-sensitized solar cells

Two different-length (6 μm and 1 μm) TiO2 nanotubes were prepared and incorporated in working electrode of dye-sensitized solar cells (DSSCs). The analyses of the electrochemical impedance spectra of cells demonstrate that, the electron transport resistance Rw decreases and increases separately to 0.3 Ω in 6-μm-tubes-cell and to 15.1 Ω in 1-μm-tubes-cell comparing with that 1.4 Ω in P25-cell, reflecting the improved electron transport in 6-μm-tubes-cell and impeded electron transport in 1-μm-tubes-cell. The reason is ascribed to the different electron transport in working electrode due to the incorporation of nanotubes. For the 6-μm-tubes incorporation, both 1-D electron diffusion along nanotubes and nanotube percolation improve electron transport in working electrode, but they cannot improve electron transport for the 1-μm-tubes incorporation. On the contrary, the 1-μm-tubes incorporation may impede electron transport because of electron residing occurring seriously at the end of 1-μm-tubes. The results of this work will help to understand the specific nature of electron transport in TiO2 nanotubes in DSSCs.