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Proceedings Paper

Hopping conduction in high electric fields: three issues
Author(s): David Emin
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Paper Abstract

Three issues concerning phonon-assisted hopping in molecularly doped polymers are considered. The first issue is whether Arrhenius jump rates in the vicinity of room temperature arise from single-phonon or small-polaronic hopping. It is concluded that Arrhenius hopping only occurs above low temperatures through small-polaronic hopping. Second, hopping in molecularly doped polymers is compared with small-polaronic hopping of other systems. Small- polaronic hopping typically occurs between similar chemical structures whose energies are relatively insensitive to their surroundings. Thus, disorder energies experienced by carriers are often modest, values of several hundredths of an eV are common. Nonetheless, the effects of large electric fields on carrier mobilities differ significantly among disordered systems. Data reported for molecularly doped polymers is unlike that for either transition-metal-oxide or chalcogenide glasses. In no case is high-field transport well understood. Finally, I stress that steady-state flow is driven by differences in sites' quasielectrochemical potentials (QECPs). With disorder, differences of QECPs are not simply related to the driving emf. Solution of the (nonlinear) stochastic equations for the QECPs shows that bottlenecks produced by disorder result in nonohmic conduction. Solving the linearized stochastic (disordered resistor network) equations underestimates bottleneck effects. Linearization is inappropriate when intersite differences in the QECPs exceed (kappa) T.

Paper Details

Date Published: 15 October 1996
PDF: 12 pages
Proc. SPIE 2850, Organic Photorefractive Materials and Xerographic Photoreceptors, (15 October 1996); doi: 10.1117/12.254241
Show Author Affiliations
David Emin, Sandia National Labs. (United States)

Published in SPIE Proceedings Vol. 2850:
Organic Photorefractive Materials and Xerographic Photoreceptors
Stephen Ducharme; James W. Stasiak, Editor(s)

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