New possibility for an organic semiconductor: a smectic liquid crystalline semiconductor having a long conjugated core and two long alkyl chains

We report a new possibility for liquid crystalline organic semiconductors. These materials exhibit smectic liquid crystalline phases, in which the molecules assume a smectic molecular order by self-assembly. Because of the strong dispersion force among long alkyl chains, on cooling, smectic molecular order was retained at room temperature. A charge transport ability was also retained. The conductivity of a device having smectic liquid crystalline order is about 5610 7 that of a device with no smectic order. The current-voltage characteristic of the device has a very sharp increase at low threshold voltage (5 V). A high carrier mobility of 1.8x10(-2) was observed in the smectic phase of one of the compounds studied (e).