Disorder controlled hole transport in MEH-PPV

We analyze the correlation between nanostructure and charge transport in poly(2-methoxy,5-(2′ethyl-hexyloxy)-p-phenylene vinylene) (MEH-PPV) films. The MEH-PPV films prepared in toluene (TL) as well as chlorobenzene (CB) solvents were investigated using the time-of-flight method and x-ray scattering. Nondispersive hole transport was observed at room temperature in devices prepared from both solutions. The field and temperature-dependent mobility were analyzed by the Gaussian disorder transport model. The positional disorder parameter in CB is larger than that in TL films. Both energy and position disorders affect the transport property in the devices from CB whereas only energy disorder affects this property in devices from TL. Correspondingly, according to the x-ray scattering measurements, the TL-cast films have larger chain-packed domains and less order-disorder transition interfaces than those for CB-cast films, along the surface normal, i.e., the charge transport direction.