J. Ferber et J. Luther, Modeling of photovoltage and photocurrent in dye-sensitized titanium dioxide solar cells, J PHYS CH B, 105(21), 2001, pp. 4895-4903
By means of two-dimensional simulation calculations, a detailed analysis of
the nanocrystalline TiO2 dye sensitized solar cell (DSC) has been performe
d. A simplified scheme of the nanoporous structure, which is treated as if
the TiO2 film is a continuous medium, is used for modeling. On the basis of
material parameters, the model permits the determination of steady-state c
harge-carrier distributions, the calculation of I-V curves under illuminati
on, dark characteristics, and the spectral response of a DSC. The spatial r
esolution of the model allows for the answer to the question of the spatial
distribution of both the electric and the electrochemical potential in the
cell. Thus, a deeper insight into the operation mechanism of a DSC is obta
ined. Nonnegligible drift currents are found. It is shown quantitatively th
at the electric potential drops mainly at the TCO/TiO2 interface and not at
a Helmholtz layer. The role of the dark interfacial electrical potential d
ifference (built-in potential) for the function of a DSC is discussed. It i
s shown that, contrary to a conventional p-n junction solar cell, higher ph
otovoltages than those of the dark interfacial electrical potential differe
nce can be obtained.