High electron mobility of 0.1cm2V−1s−1 in the highly ordered columnar phase of hexahexylthiotriphenylene

Negative charge carrier transport has been investigated in the columnar mesophases of 2,3,6,7,10,11-hexahexylthiotriphenylene (HHTT), (the best-known conducting discotic liquid crystal because of its high bulk hole mobility) using the time-of-flight method. It was shown that fast electron transport takes place in the highly ordered helical columnar phase. The electron mobility was 0.08cm2V−1s−1 at 45°C, which was the same as the hole mobility reported previously. Electron transport was also observed in the lower-order columnar hexagonal phase, but an additional slow transit appeared in the transient photocurrents, suggesting ionic transport originating from ionized impurities.