Deciphering the metal-C60 interface in optoelectronic devices: Evidence for C60 reduction by vapor deposited Al

Dallas L. Matz, Erin L Ratcliff, Jens Meyer, Antoine Kahn, Jeanne E Pemberton

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

The formation of interfacial midgap states due to the reduction of buckminsterfullerene (C60) to amorphous carbon upon subsequent vapor deposition of Al is confirmed using Raman spectroscopy and X-ray, ultraviolet, and inverse photoemission spectroscopies. We demonstrate that vapor deposition of Al results in n-type doping of C60 due to an electron transfer from Al to the LUMO of C60, resulting in the formation of midgap states near the C60 Fermi level. Raman spectroscopy in ultrahigh vacuum clearly identifies the presence of the C60 anion radical (C60•-) as well as amorphous carbon created by further degradation of C60•-. In contrast, the interface formed by vapor deposition of Ag shows only a slight Ag/C60 interfacial charge displacement with no evidence for complete metal-to-C 60 electron transfer to form the anion radical or its further degradation products. These results confirm previous speculations of metal-induced chemical damage of C60 films after Al deposition, which is widely suspected of decreasing charge collection efficiency in OPVs, and provide key insight into charge collection at metal/organic interfaces in such devices.

Original languageEnglish (US)
Pages (from-to)6001-6008
Number of pages8
JournalACS Applied Materials and Interfaces
Volume5
Issue number13
DOIs
StatePublished - Jul 10 2013

Fingerprint

Vapor deposition
Optoelectronic devices
Metals
Vapors
Amorphous carbon
Anions
Raman spectroscopy
Negative ions
Fullerenes
Degradation
Electrons
Ultrahigh vacuum
Photoelectron spectroscopy
Fermi level
Doping (additives)
X rays

Keywords

  • charge displacement
  • charge transfer
  • electron spectroscopy
  • fullerene
  • organic photovoltaic
  • Raman spectroscopy

ASJC Scopus subject areas

  • Materials Science(all)

Cite this

Deciphering the metal-C60 interface in optoelectronic devices : Evidence for C60 reduction by vapor deposited Al. / Matz, Dallas L.; Ratcliff, Erin L; Meyer, Jens; Kahn, Antoine; Pemberton, Jeanne E.

In: ACS Applied Materials and Interfaces, Vol. 5, No. 13, 10.07.2013, p. 6001-6008.

Research output: Contribution to journalArticle

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