Experimental and theoretical studies of the electronic structure of substituted and unsubstituted poly(para-phenylenevinylene) (PPV)

ulbar M. Fahlman*, O. Lhost, F. Meyers, Jean-Luc Bredas, S. C. Graham, R. H. Friend, P. L. Burn, A. B. Holmes, K. Kaeriyama, Y. Sonoda, M. Lögdlund, S. Stafström, W. R. Salaneck

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

The electronic structure of poly(p-phenylenevinylene) and that of its ring-substituted derivatives, poly(2,5-diheptyl-1,4-phenylenevinylene), poly(2,5-dimethoxy-1,4-phenylenevinylene), and poly(2-methoxy-5-(2′-ethylhexoxy)-1,4-phenylenevinylene), are studied by Ultraviolet Photoelectron Spectroscopy, UPS, and X-ray Photoelectron Spectroscopy, XPS. It is observed by UPS that the π-bands closest to the valence band edge are strongly affected by the presence of the substituents. The influence of the side groups on the experimental spectra is studied theoretically using the Valence Effective Hamiltonian, VEH, model. Calculations are carried out on isolated polymer chains, including full treatment of the aliphatic side groups. Particular attention is paid to the effect of chain torsion angles on the π-band edge. For the diheptyl derivative, the experimental results can be explained on the basis of side-group-induced torsions of the phenylene rings along the backbone, which influence the π-band widths and contribute to differences in both optical absorption threshold and binding energy of the valence band edge. For the alkoxy derivatives, the side groups cause strong modifications in the shape of the upper two occupied π-bands, which results in significant changes in the electronic density of states.

Original languageEnglish (US)
Pages (from-to)263-268
Number of pages6
JournalSynthetic Metals
Volume55
Issue number1
DOIs
StatePublished - Mar 15 1993

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

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