between samples, since it is sensitive to subtleties in the
preparation and history of each sample. Under illumination, the
electrode saturates and the potential shifts negatively to values
close to ECBM, and the potentials converge for replicate samples to
quite similar values.
Plotted on the same potential scale, the OCV traces show that in
this electrolyte the CBM of ZnO lies at a more negative potential
than that of TiO2 by about 0.1 V. This would tend to block the
desired electron transfer from TiO2 to ZnO in a DSSC device based
on a hybrid of these two materials. However, doping ZnO with 10 at
% Co results in a positive shift of the CBM by about 0.15 V, while
doping TiO2 with Zr results in a negative shift of about 0.1 V at the
5 at% doping level and 0.2 V at the 10% doping level. Together, the
dopants of the two materials combine to give a driving force of
more than 0.2 V for electron transfer from Zr-doped TiO2 to Codoped
ZnO.