Fast ambipolar carrier transport in smectic phases of phenylnaphthalene liquid crystal

Abstract

The carrier transport of a new calamitic liquid crystal, i.e., ${\text{2-(4}}^{\prime }$ -octylphenyl)6-dodecyloxynaphthalene (8-PNP-O12) was investigated by the time-of-flight technique. The fast ambipolar electronic conduction was observed in two smectic phases of 8-PNP-O12. The carrier mobilities were determined to be ${\text{1.6×10}}^{\text{−3}}\hspace{0.17em}{\mathrm{cm}}^{\mathrm{2}}\mathrm{/V\cdot s}$ in the lower temperature smectic phase (Sm1) between 79 and 100 °C and to be ${\text{2.5×10}}^{\text{−4}}\hspace{0.17em}{\mathrm{cm}}^{\mathrm{2}}\mathrm{/V\cdot s}$ in the higher temperature phase (Sm2) between 100 and 121 °C, regardless of carrier signs, i.e., electron and hole. The slower ambipolar transport was observed in isotropic phase as well, whose mobility was ${\text{8×10}}^{\text{−5}}\hspace{0.17em}{\mathrm{cm}}^{\mathrm{2}}\mathrm{/V\cdot s}.$ These mobilities were independent of applied electric fields and temperature.