  Charge-carrier transport in a paradigmatic semicrystalline polymer
semiconductor (P3HT) is important for both fundamental understanding and
applications. In samples with enhanced structural disorder due to ad-hoc point
defects, the mobility displays rich behavior as a function of electric field
(F) and temperature (T). At low T, the mobility increases with the applied
field, but upon further increasing T, the field-dependence becomes shallower.
Eventually, at the highest T considered, the slope changes sign and the
mobility then decreases with the field. This phenomenon can be interpreted with
our model as a result of the competition between intrachain conductive-like
transport (which slows on increasing F) and interchain activated transport
(which is faster at higher F). The former is controlling at high T where
interchain hops are strictly limited to nearest-neighbor monomers on adjacent
chains. At low T, instead, interchain hops to distant sites are allowed and
control the positive correlation of the mobility with the field.
