Bipolar carrier transport in a lamello-columnar mesophase of a sanidic liquid crystal

The lamello-columnar mesophase of a [1]benzothieno[3,2-b][1]benzothiophene-2,7-dicarboxylate (BTBT) derivative has been investigated by means of X-rays on an aligned sample. The most probable model of molecular organisation corresponds to an assembly of microcolumns made of alternatively crossed molecules, within the smectic layers. The preliminary investigation by a time-of-flight technique revealed that the mesophase exhibits a bipolar charge transport, with comparable electron and hole mobility values in the order of 2 × 10−3 cm2 V−1 s−1. The high mobility values obtained for this disordered smectic phase can be explained by the improved π-overlap between sandwich-like packed aromatic moieties in the short-range columnar stackings.