Temperature-independent hole mobility in discotic liquid crystals

Experimental measurements are presented of the hole mobilities of four conj ugated discotic systems, forming columnar liquid crystals, as a function of temperature. The measurements cover the crystalline/glassy phase and mesop hase of these materials. It is a remarkable fact that the mobility is almos t independent of temperature in the range 30 degreesC-170 degreesC. Various explanations of a weak temperature dependence exist and these are explored . They include the small polaron of Holstein in the nonadiabatic limit and the effect of the dynamic disorder present in the system. (C) 2001 American Institute of Physics.