Electric-field dependence of mobility in conjugated polymer films

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Abstract
It has been suggested that Poole–Frenkel behavior, i.e., the linear dependence of the log of the mobility μ on the square root of the electric-field intensity, found for many conjugated polymer films is due to the interaction between the charge carriers and randomly distributed permanent dipoles. However, the dipole concentration in the polymers is much too small to achieve this. We show that introduction of short-range correlation between the energies of the hopping sites, on the scale of the coherence length measured by x rays, can account for the field and temperature dependence of films of poly(2-methoxy,5-(2′-ethyl-hexoxy)–p-phenylene vinylene), a representative conjugated polymer. We investigate also the effects of inhomogeneity on the field and temperature dependence of μ.