Keywords and Phrases
Charge transport in MDPs; Energetic disorder; Gaussian Disorder Model; Geometrical disorder; Lattice Gas Model; Reorganization energy
"The mobility of photo-injected charge carriers in molecularly-doped polymers (MDPs) exhibits a commonly observed, and nearly universal Poole-Frenkel field dependence, µ ~ exp [square root (ß0E)], that has been shown to arise from the correlated Gaussian energy distribution of transport sites encountered by charges undergoing hopping transport through the material. Analytical and numerical studies of photo-injected charge transport in these materials are presented here with an attempt to understand how specific features of the various models developed to describe these systems depend on the microscopic parameters that define them. Specifically, previously published time-of-flight mobility data for the molecularly doped polymer 30% DEH:PC (polycarbonate doped with 30 wt.% aromatic hydrazone DEH) is compared with direct analytical and numerical predictions of five disorder-based models, the Gaussian disorder model (GDM) of Bäassler, and four correlated disorder models introduced by Novikov, et al., and by Parris, et al. In these numerical studies, disorder parameters describing each model were varied from reasonable starting conditions, in order to give the best overall fit. The uncorrelated GDM describes the Poole-Frenkel field dependence of the mobility only at very high fields, but fails for fields lower than about 64 V/µm. The correlated disorder models with small amounts of geometrical disorder do a good over-all job of reproducing a robust Poole-Frenkel field dependence, with correlated disorder theories that employ polaron transition rates showing qualitatively better agreement with experiment than those that employ Miller-Abrahams rates. In a separate study, the heuristic treatment of spatial or geometric disorder incorporated in existing theories is critiqued, and a randomly-diluted lattice gas model is developed to describe the spatial disorder of the transport sites in a more realistic way"--Abstract, page iii.
Parris, Paul Ernest, 1954-
Pringle, Oran Allan
Medvedeva, Julia E.
Dunlap, David H.
Ph. D. in Physics
Missouri University of Science and Technology
x, 132 pages
© 2015 Amrita Roy Chowdhury, All rights reserved.
Dissertation - Open Access
Library of Congress Subject Headings
Polymers -- Analysis
Charge transfer -- Mathematical models
Electronic OCLC #
Roy Chowdhury, Amrita, "Analytical and numerical studies of photo-injected charge transport in molecularly-doped polymers" (2015). Doctoral Dissertations. 2459.