Study on charge mobility of hexathiapentacene and its selenium analogs

The relationship between molecular geometries, crystal structures and charge mobilities of hexathiapentacene (HTP) and three of its derivatives (2Se-HTP, 4Se-HTP, 6Se-HTP) were studied using the density functional theory combined with a hopping mechanism at the molecular and crystal level. The effect of Se substitution on the charge mobility was discussed. The calculated results showed that the derivatives exhibit good planarity and the molecular geometries show little variation during the charge transfer process. The electron mobility is 1.20 cm2 V-1 S-1 for HTP and 2.30 cm2 V-1 S-1 for 6Se- -HTP, which are much larger than the corresponding hole ones, indicating that HTP and 6Se-HTP are good candidates for n-type organic semiconductors. However, 2Se-HTP and 4Se-HTP have comparable hole and electron motilities and are suitable for ambipolar semiconductors.