Frequency dependent carrier mobility in polymer LED's

The charge mobility in polymer LED's depends on the polymer and its packing. In the latter various length scales play a role. To study this aspect, we performed dielectric spectroscopy as function of electric field and temperature on OC1C10-poly(p-phenylene vinylene). At low frequencies the mobility (mu) is mainly determined by the energetic disorder of the weakest link. Around 100 GHz mu has increased by 6 orders of magnitude and the field dependence has changed significantly. At these high frequencies, which in this case are representative for the pair limit, the field dependence shows that still appreciable energy barriers have to be overcome. Together these data allow a detailed characterization of the charge transport in the LED.