Analysis of hole transport in a polyfluorene-based copolymer- evidence for the absence of correlated disorder

The presence of spatial correlation between the disordered transport site energies in semiconducting polymers used in organic electronic devices is known to affect the mobility. However, it is not established whether such a correlation is present in relevant polymers. We study hole transport in a polyfluorene-based copolymer and provide evidence for the absence of spatially correlated disorder in this material, based on an analysis of the current-voltage characteristics of sandwich-type devices. Distinguishing correlated from uncorrelated disorder, which we achieve on the basis of the hopping site density, is shown to be highly relevant for the development of quantitative device models.