Enhanced conduction in the discotic mesophase

This paper summarises our recent investigations on mechanically robust materials with columnar hexagonal order. Initially we address the problem of poor field injection of charge carriers from an electrode. We show that, by using the appropriate cell treatment along with the use of more ordered columnar phases, the DC dark conductivity can be improved by up to five orders of magnitude over that of materials exhibiting a conventional Col(h) phase. Charge carrier mobilities were determined by time of flight photoconduction for the columnar hexagonal plastic phase of 2,3,6,7,10,11-hexakis(propyloxy)triphenylene (HAT3, 0.015 cm(2) V-1 s(-1) at 130degreesC). The mobilities and their temperature dependence are discussed with reference to the series of hexaalkoxytriphenylenes and a highly ordered CPI stabilised system.