Transport properties of highly aligned polymer light-emitting diodes - art. no. 012201

We investigate hole transport in polymer light-emitting diodes in which the emissive layer is made of liquid-crystalline polymer chains aligned perpen dicular to the direction of transport. Calculations of the current as a fun ction of time via a random-walk model show excellent qualitative agreement with experiments conducted on electroluminescent polyfluorene demonstrating nondispersive hole transport. The current exhibits a constant plateau as t he charge carriers move with a time-independent drift velocity, followed by a long tail when they reach the collecting electrode. Variation of the par ameters within the model allows the investigation of the transition from no ndispersive to dispersive transport in highly aligned polymers. It turns ou t that large interchain hopping is required for nondispersive hole transpor t and that structural disorder obstructs the propagation of holes through t he polymer film.