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

Abstract

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 $2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}{\mathrm{cm}}^{2}∕\mathrm{V}\phantom{\rule{0.2em}{0ex}}\mathrm{s}$. Its temperature dependence is consistent with a ${T}^{\ensuremath{-}n}$ power law, with the factor $n$ being dependent on the electric field. The drift velocity is a linear function of the electric field below ${10}^{\ensuremath{-}5}\phantom{\rule{0.3em}{0ex}}\mathrm{V}∕\mathrm{cm}$ 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.