Low Energy Electron Degradation of Poly(p-phenylenevinylene)

Bröms, Per; Johansson, Nils; Gymer, R. W.; Graham, Stephen C.; Friend, Richard H.; Salaneck, W. R.

doi:10.1002/(sici)1521-4095(199907)11:10<826::aid-adma826>3.0.co;2-n

Cited by 9 publications

(7 citation statements)

References 6 publications

(6 reference statements)

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“…Their disappearance indicates that electron bombardment results in destruction of delocalized electronic states. Similar conclusions were drawn from UPS investigations of electron irradiation of poly( p -phenylenevinylene) films . The broadening of the 4.0 eV feature is consistent with a widening distribution of effective conjugation lengths (i.e., less homogeneous sample) as the P3HT is degraded.…”

Section: Resultssupporting

confidence: 79%

“…Especially important is the electron dose required for significant decomposition and the nature of the resulting organic layer. These are critical issues with respect to the fabrication of organic electronic devices, since polymeric films may inadvertently be exposed to electrons during electron beam evaporation of metal electrodes or during surface analysis. , In one of the few published investigations, Bröms et al used photoluminescence and ultraviolet photoelectron spectroscopy (UPS) to study the effects of electron impact on poly( p -phenylenevinylene) films. The authors concluded that electron irradiation facilely leads to destruction of conjugation and loss of delocalization and causes a dramatic decrease in fluorescence intensity.…”

Section: Introductionmentioning

confidence: 99%

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Electron Irradiation of Poly(3-hexylthiophene) Films

2004

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The effects of low-energy electron irradiation on spin-coated films of regioregular poly(3hexylthiophene) have been studied with fluorescence, mass spectrometry, and a variety of electron spectroscopies, including photoemission. Electron impact by 180 eV electrons causes a decrease in photoluminescence intensity, broadening of the thiophene ring valence electronic state features, and diminution in intensity of the peaks due to π electrons delocalized along the backbone. Electron bombardment also results in a decrease in the X-ray photoelectron spectroscopy sulfur-to-carbon ratio, but only minor shifts in the binding energies of the C 1s and S 2p peaks occur. Quadrupole mass spectrometry has been used to detect electron-stimulated desorption from the polymer films. Ionic desorption includes S -, SH -, S + , and CxHy + species. Auger electron spectroscopy confirms removal of sulfur from the near-surface region by a 5 keV electron dose of 1.8 × 10 18 electrons/cm 2 , and electron energy loss spectroscopy suggests formation of a graphitic surface.

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Section: Resultssupporting

confidence: 79%

Section: Introductionmentioning

confidence: 99%

Electron Irradiation of Poly(3-hexylthiophene) Films

2004

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“…The degree of quenching rates and blue-shift in spectra depends on the evaporation method (e-beam or thermal), the evaporation rate, the molecular weight, and chemical structures of the material, to name a few. For the case of e-beam and thermal evaporation, the disruption is primarily caused by secondary electrons and thermal electrons respectively [20].…”

Section: Resultsmentioning

confidence: 99%

Improving organic/electrode interface in organic light-emitting diodes by soft contact Iamination

Lee

Hsu

2005

Proceedings of the Institution of Mechanical Engineers, Part N:

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Organic light-emitting diodes (OLEDs), with few exceptions, are fabricated in the standard way of sequentially depositing active layers and electrodes onto a substrate. The conventional devices have 'a detrimental layer' at the interface between the organic and the top metal electrode because evaporation results in metal in-diffusion and chemical disruption at the metal-organic interface. Here, a different approach is introduced to construct OLEDs: soft contact lamination (SCL) is based on physical lamination of thin metal electrodes supported by an elastomeric layer against the electroluminescent organic layer. This method produces spatially homogeneous, intimate contacts via van der Waals interaction between the metal and the organic, resulting in no chemical and physical damages to the organic. Devices fabricated by SCL are shown to have no detrimental layer and fewer luminescence-quenching channels than conventional devices that have evaporated top metal electrodes.

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“…In the case of electrochemical polymerization, the first step is believed to be oxidation of the monomer to its cation radical; this is followed by coupling of the radicals, which have a high concentration at the electrode, and finally CÀ ÀH bond cleavage. [22] To determine the effects of electron bombardment on electronic structure and measure possible similarity to the electron-oligomerized 3HT layer, a 350 Å film of regioregular P3HT on gold has been irradiated with 185 eV electrons, and valence and photoluminescence spectra have been measured as a function of electron dose. In the case of x-ray ''polymerization'' of condensed thiophene physisorbed on Ag(111), it has been observed that increasing the temperature of the sample, while staying below multilayer desorption temperature, increases the rate of polymerization.…”

Section: Beam-oligomerized 3-hexylthiophene 1363mentioning

confidence: 99%

“…In the case of x-ray ''polymerization'' of condensed thiophene physisorbed on Ag(111), it has been observed that increasing the temperature of the sample, while staying below multilayer desorption temperature, increases the rate of polymerization. [22] Poly(3-hexylthiophene) is soluble in chloroform; our attempts to dissolve electron-and x-ray-formed films in this solvent have failed to remove them completely. Electron beams are known to be destructive to organic films and conjugated polymers.…”

Section: Beam-oligomerized 3-hexylthiophene 1363mentioning

confidence: 99%

Electronic Properties and Morphology of Beam‐Oligomerized 3‐Hexylthiophene

Ahn

Whitten

2003

Journal of Macromolecular Science, Part A

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A novel means of lithographically forming fluorescent oligothiophene patterns is demonstrated. MgKa 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 À9 cm À1 ohm À1 , consistent with the formation of islands of conjugated material surrounded by a less electronically delocalized,

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Low Energy Electron Degradation of Poly(p-phenylenevinylene)

Cited by 9 publications

References 6 publications

Electron Irradiation of Poly(3-hexylthiophene) Films

Electron Irradiation of Poly(3-hexylthiophene) Films

Improving organic/electrode interface in organic light-emitting diodes by soft contact Iamination

Electronic Properties and Morphology of Beam‐Oligomerized 3‐Hexylthiophene

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