Correlated polaron transport in a quasi-one-dimensional liquid crystal

Charge-carrier transport in the columnar phase of the discotic liquid crystal, hexapentyloxytriphenylene, has been investigated by the time-of-flight technique over a range of temperatures and electric fields. The hole mobility was found to be temperature and electric-field-dependent with a maximum value of 2×10^-3cm²∕V0.2em0exs. Its temperature dependence is consistent with a T^-n power law, with the factor n being dependent on the electric field. The drift velocity is a linear function of the electric field below 10^-50.3em0exV∕cm and tends to saturate at higher fields. These results were interpreted in the framework of correlated polaron motion as described by the nonadiabatic low-temperature limit of Holstein's polaron theory developed for a one-dimensional diatomic chain.