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Models of Electron-Hole Screening and Exciton Binding in Conjugated Polymers

Published online by Cambridge University Press:  10 February 2011

David Yaron ,
Eric Moore  and
Benjamin Gherman
David Yaron
Affiliation:
Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213
Eric Moore
Affiliation:
Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213
Benjamin Gherman
Affiliation:
Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213
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Abstract

The use of semi-empirical quantum chemistry to calculate the exciton binding energy of conjugated polymers is discussed. Both the Pariser-Parr-Pople (PPP) model with Ohno parameterization and the models present in the MOPAC program overestimate the exciton binding energy relative to that observed in solid-state materials. Inclusion of Coulomb screening from adjacent chains may correct this overestimation. The solvation energy of a point charge in polyacetylene is calculated as 0.9eV, using Hartree-Fock theory to describe the polarization induced in the solvent chains. It is argued that including screening by modifying the electron-electron interaction energy of the PPP model introduces physically unreasonable side effects and is not consistent with the 0.9eV solvation energy of a point charge. Electron-hole screening models are then discussed along with the need to consider the relative time scales of the electron-hole motion and the dielectric response.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 413: Symposium W – Electrical, Optical, and Magnetic Properties of Organic Solid State Materials III , 1995 , 541
Copyright
Copyright © Materials Research Society 1996

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