Field dependence of hole mobilities in chloro-aluminum phthalocyanine

Drift mobility measurements were performed on the hole-transport organic semiconductor chloro-aluminum phthalocyanine using a time-of-flight technique. The photocurrent transients were featureless decay curves and transit times were determined from the logarithmic representation of photocurrent versus time. The dependence of drift mobility on field was examined in order to elucidate the charge transport mechanism. The form of this dependence over the widest field range applied indicates the operation of a field-assisted hopping mechanism with the presence of both energetic and positional disorder according to the formalism developed by Bässler and co-workers.