Fast Hole Transport in a New Calamitic Liquid Crystal of 2-(4′-Heptyloxyphenyl)-6-Dodecylthiobenzothiazole

Abstract

The carrier transport in different phases of a new photoconductive calamitic liquid crystal, 2-(4\ensuremath{'}-heptyloxyphenyl)-6-dodecylthiobenzothiazole was studied by the time-of-flight technique: In the smectic A phase, a fast hole transient photocurrent was obtained in a nondispersive manner, in which the mobility was as high as $5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}\phantom{\rule{0ex}{0ex}}{\mathrm{cm}}^{2}/\mathrm{V}\mathrm{s}$ and independent of applied electric field; in the isotropic phase, however, slower carrier transport was observed, probably due to positive or negative ions, and their mobilities were as low as ${10}^{\ensuremath{-}5}\phantom{\rule{0ex}{0ex}}{\mathrm{cm}}^{2}/\mathrm{V}\mathrm{s}$. These experimental results demonstrate the importance of local molecular alignment in creating the fast electronic conduction in calamitic liquid crystals.