The carrier transport in different phases of a new photoconductive calamitic liquid crystal, 2-(4′-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 $5\times {10}^{-3\mathrm{}}{\mathrm{cm}}^2/\mathrm{V}\mathrm{s}$ 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 ${10}^{-5\mathrm{}}{\mathrm{cm}}^2/\mathrm{V}\mathrm{s}$. These experimental results demonstrate the importance of local molecular alignment in creating the fast electronic conduction in calamitic liquid crystals.

• Received 24 June 1996

DOI:https://doi.org/10.1103/PhysRevLett.78.2184