  A measurement method of constant-current-discharging voltage decay is
established to characterize the band bending effect in the heterojunction of
conducting glass/TiO2 for typical dye-sensitized solar cells. Furthermore, a
dark-state electron transport regarding the TiO2 conduction band bending is
proposed based upon the viewpoints of thermionic emission mechanism, which
suggests an origin of the band bending effect in a theoretical model. This
model quantitatively agrees well with our experimental results and indicates
that both the Fermi level decay in TiO2 and the potential difference across the
heterojunction will lead to the TiO2 conduction band bending downwards.

Chemical Physics;Materials Science;Optics