Hole Transport in Hydrazone Doped Polymers

Abstract

Hole mobilities have been measured in poly(styrene) doped with a series of hydrazone (HDZ) molecules with different dipole moments. The results are described by a formalism based on disorder. The formalism is premised on the argument that charge transport occurs by hopping through a manifold of localized states that are distributed in energy. The parameters of the formalism are σ, the energy width of the hopping site manifold or DOS (density-of-states), µ0 a prefactor mobility, and Σ the degree of positional disorder. The results show that the widths are between 0.098 and 0.113 eV, increasing with increasing dipole moment. The widths are described by an argument based on dipolar disorder. The argument is that the total width of the DOS is comprised of a dipolar component and a van der Waals component. Describing the dipolar component by the model of Young leads to the conclusion that the van der Waals components are approximately 0.091 eV. The prefactor mobilities are between 6 and 9×10-3 cm2/ Vs. Values of Σ are approximately 1.5. Compared to other classes of doped polymers with similar dipole moments, the relatively low mobilities of these materials are attributed to the high values of the van der Waals components and the low prefactor mobilities. The degree of positional disorder is similar to literature values reported for a wide range of doped polymers.