Photoconductivity of liquid crystalline derivatives of pyrene and carbazole

Two structurally related discogens containing either pyrene (1a) or carbazole (2a) were investigated by thermal, XRD, spectroscopic, and time-of-flight (TOF) methods. Experiments demonstrated for 1a a narrow range Colh phase, which easily forms a glass state at ambient temperature. TOF measurements showed an ambipolar charge transport for 1a with the mobilities on the order of 10−3 cm2 V−1 s−1. The carbazole 2a has two enantiotropic phases (Crcol and Colh) and behaves as a p-type semiconductor. The activation energy for positive charge mobility in 1a was found to be 0.10 ± 0.01 eV.