Chemical states and electronic properties of the interface between aluminium and a photoluminescent conjugated copolymer containing europium complex

Q. J. Cai, Q. D. Ling, S. Li, F. R. Zhu, Wei Huang, E. T. Kang, K. G. Neoh

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10 Scopus citations

Abstract

The chemical states and electronic properties of the interface between thermally evaporated aluminium and a photoluminescent conjugated copolymer containing 9,9′-dihexylfluorene and europium complex-chelated benzoate units in the main chain (PF6-Eu(dbm) 2 phen) were studied in situ by X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). The changes in C 1s, Eu 3d, N 1s, and Al 2p core-level lineshapes with progressive deposition of aluminium atoms were carefully monitored. Aluminium was found to interact with the conjugated backbone of the copolymer to form the Al carbide, Al-O-C complex, and Al(III)-N chelate at the interface. In addition, the europium ions were reduced to the metallic state by the deposited aluminium atoms, which were oxidized and chelated by the 1,10-phenanthroline ligands (phen). The changes in chemical states at the interface suggest that the intramolecular energy transfer process in this copolymer had been affected. Moreover, aluminium also interacted with the bulk-adsorbed oxygen, which migrates to the surface in response to the deposition of aluminium atoms, to form a layer of metal oxides. On the other hand, the evolution of the UPS spectra suggests that the π-states of the conjugated system were affected and an unfavorable dipole layer was induced by the deposited aluminium atoms.

Original languageEnglish
Pages (from-to)399-408
Number of pages10
JournalApplied Surface Science
Volume222
Issue number1-4
DOIs
StatePublished - 30 Jan 2004
Externally publishedYes

Keywords

  • Aluminium
  • Conjugated copolymer
  • Europium
  • Intramolecular energy transfer
  • Photoluminescent
  • UPS
  • XPS

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