Increased order and improved hole mobility in MEH-PPV thin films by removing shortest chains

The effect of polydispersity on morphology and charge transport in MEH-PPV drop-cast films was investigated using grazing incidence X-ray diffraction and time-of-flight. Removing short chain segments promoted the capability of crystallization resulting in higher hole mobility and non-dispersive transport down to lower temperatures. The slope for the Poole–Frenkel relationship at 298K was increased, and its change with temperature decreased, indicating reduced spatial inhomogeneity. Analysis using Bässler’s Gaussian disorder model, found minimal impact on energy disorder and infinite temperature zero field mobility. A good fit for hopping site separation and spatial disorder was only possible for the lower polydispersity device, suggesting that the lower polydispersity films have less mesoscopic inhomogeneity.