Effect of Pretransitional Organization in Chiral Nematic of Oligothiophene Derivatives on Their Carrier Transport Characteristics

We have synthesized three phenylquaterthiophene derivatives (liquid-crystalline semiconductors that exhibit a chiral nematic phase) and investigated their carrier transport characteristics in the chiral nematic phases with the time-of-flight technique. In contrast to the ionic nature of negative carrier transport, positive carrier transport in the chiral nematic phases of these compounds should be attributed to electronic charge carrier transport. The temperature dependence of the positive carriers in the chiral nematic phases of these compounds were strongly affected by a pretransitional smectic order formation.