Lateral intermolecular
charge transfer between photosensitizers
on metal oxide substrates is important for the understanding on the
overall working principles of dye-sensitized systems. Such studies
usually concentrate on either hole or electron transfer separately
and are conducted in solvents with a high dielectric constant (εs) that are known, however, to show a drastic
decrease of the local dielectric constant close to the metal oxide
surface. In the present study, both hole and electron hopping between
organic donor–acceptor photosensitizers was experimentally
investigated on PB6 dye-sensitized mesoporous ZrO2films.
The donor (close to the surface) and acceptor (away from surface)
subunit of the PB6 dye were observed to be involved in hole and electron
hopping, respectively. Hole and electron transfer kinetics were found
to differ remarkably in high-εssolvents,
but similar in solvents with εs<
12. This finding indicates that low-εssolvents maintain similar local dielectric constant values
close to, and further away from, the semiconductor surface, which
is different from the previously observed behavior of high dielectric
constant solvents at a metal oxide interface.