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Proceedings Paper

Role of disorder in characterizing the ubiquitous temperature, concentration, and field dependencies of charge transport in molecularly doped polymers
Author(s): David H. Dunlap
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Paper Abstract

Over the last two decades, experimental investigations of the mobility of photo-injected charges in a wide variety of molecularly doped, pendant-, and main-chain polymers, and vapor deposited molecular glasses have shown that the mobility at high electric fields is universally described by the Poole-Frenkel law, micrometers equals exp(- (Delta) /kT) exp((gamma) (root)E). With few exceptions, the activation energy (Delta) is about 0.5eV, and the Poole-Frenkel factor (gamma) is a function of temperature which follows the empirical relation (gamma) equals B(1/kT - 1/kT0), where B approximately equals 4 X 10-4(e2Vcm)1/2. The remarkable similarity among experiments suggests a mechanism for these dependencies which is largely based on a feature these materials have in common--lack of a crystal structure. Each material consists of a highly disordered array of active molecules, which is believed in turn to give rise to large energetic fluctuations along the conduction pathways. Computer simulations of hopping transport on a disordered lattice have shown behavior in agreement with many aspects of experiment, lending support to the concept of a disorder-based mechanism. To increase our understanding of the high-field effects of disorder, we have developed a self-consistent algorithm with which the field dependence of the mobility in disordered systems may be calculated analytically. We examine the field dependence within this framework, and suggest that the (root)E- dependence may be understood when the theory of Scher and Montroll is applied to a length scale which the hopping matrix may be considered to be of a lower dimensionality.

Paper Details

Date Published: 23 August 1995
PDF: 11 pages
Proc. SPIE 2526, Xerographic Photoreceptors and Photorefractive Polymers, (23 August 1995); doi: 10.1117/12.217305
Show Author Affiliations
David H. Dunlap, Univ. of New Mexico (United States)

Published in SPIE Proceedings Vol. 2526:
Xerographic Photoreceptors and Photorefractive Polymers
Stephen Ducharme; Paul M. Borsenberger, Editor(s)

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