Carrier mobility in rubrene-doped 4-cyano-4′-pentylbiphenyl studied by the time-of-flight method

We have investigated the transient photocurrent of rubrene-doped nematic liquid crystal using a time-of-flight examination. Drift mobilities on the order of 10(-6) cm(2)/V s were obtained for both positive and negative carriers. The minimal dependence of the rubrene concentration on the drift mobility is indicative of the ionic conduction as carrier transport process. The product of the drift mobility and the viscosity obeys the Walden rule, further supporting the ionic carrier transport process. (C) 2013 AIP Publishing LLC.