Doctoral Dissertations

Keywords and Phrases

Charge transport in MDPs; Energetic disorder; Gaussian Disorder Model; Geometrical disorder; Lattice Gas Model; Reorganization energy

Abstract

"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.

Advisor(s)

Parris, Paul Ernest, 1954-

Committee Member(s)

Peacher, Jerry
Pringle, Oran Allan
Medvedeva, Julia E.
Dunlap, David H.

Department(s)

Physics

Degree Name

Ph. D. in Physics

Publisher

Missouri University of Science and Technology

Publication Date

Fall 2015

Pagination

x, 132 pages

Note about bibliography

Includes bibliographic references (pages 129-131).

Rights

© 2015 Amrita Roy Chowdhury, All rights reserved.

Document Type

Dissertation - Open Access

File Type

text

Language

English

Subject Headings

Polymers -- Analysis
Charge transfer -- Mathematical models
Conducting polymers

Thesis Number

T 10836

Electronic OCLC #

936209242

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