A crystalline organic semiconductor grown from a mesophase: A test of polaron band theory

We find that the hole mobility of the crystal smectic phases of the liquid crystal 1,4-di-(5-n- tridecylthien-2-yl)-benzene increases exponentially with decreasing temperature. While qualita- tively consistent with transport via polaron bands, we find that it is quantitatively difficult to explain the data with physically realistic parameters. In particular, the data demand either quite large typical optical phonon frequencies and/or phonon bandwidths. We also find evidence that an unusually highly ordered high temperature smectic-F phase templates the formation of crystalline smectic phases, which may have implications for device development.