Photoconductivity of liquid crystalline derivatives of pyrene and carbazole

Abstract

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 Col_h 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 (Cr_col and Col_h) 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.