Electronic Properties and Morphology of Beam-Oligomerized 3-Hexylthiophene

Heejoon Ahn, James E. Whitten

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

A novel means of lithographically forming fluorescent oligothiophene patterns is demonstrated. MgKα x-ray and low energy electron irradiation of 3-hexylthiophene (3HT) monomer condensed on a cold metal surface result in the formation of photoluminescent films as thick as several microns. The excitation maxima for the x-ray- and electron-formed samples are 350 and 405 nm, respectively, with corresponding emission maxima of 430 and 525 nm, indicating that the films are oligomeric rather than polymeric. Ultraviolet photoelectron spectra (UPS) of 3HT monomer and beam-formed films have been compared with theoretically simulated density-of-states spectra of 3HT, thiophene, bithiophene, terthiophene, and quaterthiophene. The radiation-induced changes in the 3HT UPS valence spectra are explained by delocalization of electrons along the oligomer backbone. Comparison of the experimental UPS and simulated spectra suggests that the average conjugation length of the beam-formed films is less than six. This is consistent with the photoluminescence results. Fluorescence and atomic force microscopies of electron-formed samples show the presence of oligomerized 3HT islands residing on a less fluorescent organic background. Electrical conductivity of the beam-formed samples is low, on the order of 10-9 cm-1 ohm-1, consistent with the formation of islands of conjugated material surrounded by a less electronically delocalized, insulating background. Lack of solubility of the beam-formed films suggests that partial crosslinking and decomposition may also occur during the oligomerization process.

Original languageEnglish
Pages (from-to)1357-1368
Number of pages12
JournalJournal of Macromolecular Science - Pure and Applied Chemistry
Volume40 A
Issue number12
DOIs
StatePublished - 2003 Dec 1

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Electronic properties
Photoelectrons
Electrons
Monomers
Thiophenes
X rays
Oligomerization
Electron irradiation
Thiophene
Oligomers
Crosslinking
Atomic force microscopy
Photoluminescence
Solubility
Metals
Fluorescence
Decomposition
Radiation

Keywords

  • Lithography
  • Photoelectron spectroscopy
  • Photoluminescence
  • Polythiophene

Cite this

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abstract = "A novel means of lithographically forming fluorescent oligothiophene patterns is demonstrated. MgKα x-ray and low energy electron irradiation of 3-hexylthiophene (3HT) monomer condensed on a cold metal surface result in the formation of photoluminescent films as thick as several microns. The excitation maxima for the x-ray- and electron-formed samples are 350 and 405 nm, respectively, with corresponding emission maxima of 430 and 525 nm, indicating that the films are oligomeric rather than polymeric. Ultraviolet photoelectron spectra (UPS) of 3HT monomer and beam-formed films have been compared with theoretically simulated density-of-states spectra of 3HT, thiophene, bithiophene, terthiophene, and quaterthiophene. The radiation-induced changes in the 3HT UPS valence spectra are explained by delocalization of electrons along the oligomer backbone. Comparison of the experimental UPS and simulated spectra suggests that the average conjugation length of the beam-formed films is less than six. This is consistent with the photoluminescence results. Fluorescence and atomic force microscopies of electron-formed samples show the presence of oligomerized 3HT islands residing on a less fluorescent organic background. Electrical conductivity of the beam-formed samples is low, on the order of 10-9 cm-1 ohm-1, consistent with the formation of islands of conjugated material surrounded by a less electronically delocalized, insulating background. Lack of solubility of the beam-formed films suggests that partial crosslinking and decomposition may also occur during the oligomerization process.",
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Electronic Properties and Morphology of Beam-Oligomerized 3-Hexylthiophene. / Ahn, Heejoon; Whitten, James E.

In: Journal of Macromolecular Science - Pure and Applied Chemistry, Vol. 40 A, No. 12, 01.12.2003, p. 1357-1368.

Research output: Contribution to journalArticle

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AB - A novel means of lithographically forming fluorescent oligothiophene patterns is demonstrated. MgKα x-ray and low energy electron irradiation of 3-hexylthiophene (3HT) monomer condensed on a cold metal surface result in the formation of photoluminescent films as thick as several microns. The excitation maxima for the x-ray- and electron-formed samples are 350 and 405 nm, respectively, with corresponding emission maxima of 430 and 525 nm, indicating that the films are oligomeric rather than polymeric. Ultraviolet photoelectron spectra (UPS) of 3HT monomer and beam-formed films have been compared with theoretically simulated density-of-states spectra of 3HT, thiophene, bithiophene, terthiophene, and quaterthiophene. The radiation-induced changes in the 3HT UPS valence spectra are explained by delocalization of electrons along the oligomer backbone. Comparison of the experimental UPS and simulated spectra suggests that the average conjugation length of the beam-formed films is less than six. This is consistent with the photoluminescence results. Fluorescence and atomic force microscopies of electron-formed samples show the presence of oligomerized 3HT islands residing on a less fluorescent organic background. Electrical conductivity of the beam-formed samples is low, on the order of 10-9 cm-1 ohm-1, consistent with the formation of islands of conjugated material surrounded by a less electronically delocalized, insulating background. Lack of solubility of the beam-formed films suggests that partial crosslinking and decomposition may also occur during the oligomerization process.

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