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Advanced Characterization of the Electronic Structure of MEH-PPV

Published online by Cambridge University Press:  01 February 2011

David Keith Chambers  and
Sandra Selmic
David Keith Chambers
Affiliation:
Louisiana Tech UniversityInstitute for Micromanufacturing 911 Hergot Ave., Ruston, LA 71272,U.S.A.
Sandra Selmic
Affiliation:
Louisiana Tech UniversityInstitute for Micromanufacturing 911 Hergot Ave., Ruston, LA 71272,U.S.A.
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Abstract

In this paper, we present research results that explore the basic molecular structure, orientation, and electrical properties of the conjugated polymer poly(2-methoxy-5- (2,9-ethyl-hexyloxy)-1,4-phenylenevinylene) (MEH-PPV). The bandgap structure of MEH-PPV was investigated through optical absorption and emission spectra, and ultraviolet photoemission spectroscopy (UPS). Based on the optical absorption of MEH-PPV, the π-π* bandgap energy is 2.14eV. The emission spectrum of ITO/MEH-PPV/Al light emitting diode has a peak at 590nm in wavelength which corresponds to photon energies of 2.1eV. By using ultraviolet synchrotron radiation to investigate the highest occupied molecular orbitals (HOMO) of the MEH-PPV, the relative change in photoemission cross-section for various electron states was measured. The HOMO to Fermi level gap obtained from UPS spectra is about 3eV. The UPS measurements include angle-resolved and incident energy dependent spectra. Some indication of bulk film orientation was inferred by dispersion of incident energy dependent UPS. Disparities in these spectra imply some role for defect states, extrinsic carrier involvement, or Fermi-level pinning.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 871: Symposium I – Organic Thin-Film Electronics , 2005 , I6.20
Copyright
Copyright © Materials Research Society 2005

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