Dispersive Aspects of the High-Field Hopping Mobility of Molecularly Doped Solids with Dipolar Disorder
The time-of-flight mobility of photoinjected charges in molecularly doped polymers obeys a Poole-Frenkel law, μ ∝ exp(γ√E), which is commonly viewed as arising from hopping transport among sites with a large degree of energetic disorder. Recent theoretical investigations have focused on long-range correlations that characterize site energies when the dominant mechanism for energetic fluctuations is the interaction of charge carriers with randomly-oriented permanent dipoles of the dopant and host polymer. An exact calculation of the steady-state drift velocity vd for a one-dimensional system with correlated dipolar disorder predicts a Poole-Frenkel law similar to that observed. In order to investigate another feature commonly observed in the high-field measurements, namely, the anomalous dispersion of the current-time transients, we have performed an exact calculation of the field-dependent diffusion constant D for the same dipolar disorder model. In the bulk limit we obtain an expression D = (KT/e)∂vd/∂E that generalizes the normal Einstein relation and predicts a strongly field-dependent diffusion constant.
P. E. Parris et al., "Dispersive Aspects of the High-Field Hopping Mobility of Molecularly Doped Solids with Dipolar Disorder," Journal of Polymer Science, Part B: Polymer Physics, vol. 35, no. 17, pp. 2803-2809, John Wiley & Sons Inc., Dec 1997.
The definitive version is available at http://dx.doi.org/10.1002/(SICI)1099-0488(199712)35:17<2803::AID-POLB5>3.0.CO;2-R
Keywords and Phrases
Calculations; Charge carriers; Diffusion; Doping (additives); Mathematical models; Organic conductors; Photoconducting materials; Dipolar disorder; Einstein relation; Field dependence diffusion constant; High field hopping mobility; Poole-Frenkel law; Steady state drift velocity; Polymers
International Standard Serial Number (ISSN)
Article - Journal
© 1997 John Wiley & Sons Inc., All rights reserved.