Femtosecond Double-Pulse Excitation Study of α-Sexithienyl Film

Watanabe, Keiji; Asahi, Tsuyoshi; Fukumura, Hiroshi; Masuhara, Hiroshi; Hamano, Kouji; Kurata, Tetsuyuki

doi:10.1021/jp9733476

Cited by 13 publications

(11 citation statements)

References 30 publications

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“…However, an intense shoulder is observed near 25 000 cm -1 , suggesting that more disorder is probably present in the solid state. These spectral properties have been reported in the literature for QT 16,22 and for other unsubstituted oligothiophenes ,− ,, and have been well explained using the excitonic model, which predicts a splitting in the absorption spectra. The excitonic model has been fully described by Kasha .…”

Section: Resultssupporting

confidence: 76%

“…These studies have also allowed us to obtain a good correlation between the presence (or not) of thermochromism for the substituted polythiophenes and the conformation and rotational barriers of the repetitive units found in the polymer backbone . The spectroscopic properties of unsubstituted oligothiophenes in the solid state (specially the tetramer and the hexamer) have been widely studied in the literature. − From these results, a better understanding of the effect of intermolecular interactions on the optical properties of these molecules has been achieved. It has been found that the intermolecular interactions present in the solid state cause a Davydov splitting (excitonic splitting) in the absorption spectra of unsubstituted thiophene oligomers.…”

Section: Introductionmentioning

confidence: 97%

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Intermolecular Interactions in Conjugated Oligothiophenes. 3. Optical and Photophysical Properties of Quaterthiophene and Substituted Quaterthiophenes in Various Environments

et al. 1999

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A detailed analysis of the optical and photophysical properties of 2,2‘:5‘:2‘ ‘:5‘ ‘,2‘ ‘‘-quaterthiophene (QT), 3,3‘ ‘‘-dimethoxy-2,2‘:5‘:2‘ ‘:5‘ ‘,2‘ ‘‘-quaterthiophene (DMOQT), 3,3‘ ‘‘-dimethyl-2,2‘:5‘:2‘ ‘:5‘ ‘,2‘ ‘‘-quaterthiophene (DMQT) and 3‘,4‘ ‘-didecyl-2,2‘:5‘:2‘ ‘:5‘ ‘,2‘ ‘‘-quaterthiophene (DDQT) in various environments is reported. In solution at room temperature, the optical properties of the free molecules are obtained and discussed in terms of the effect of the substitution on the conformation adopted by each derivative in the electronic ground and first excited states. In a tetradecane matrix at 77 K, the optical properties are obtained for the isolated molecules in this rigid medium where the oligothiophenes adopt conformations similar to those found in the solid state. The optical properties of the quaterthiophene derivatives in their aggregated forms and in the solid state are also reported and discussed in terms of the substitutional effect on the intermolecular interactions, which affect the spectral and photophysical properties of the isolated molecules. For the first time, a β,β‘-disubstituted oligothiophene (DMQT) showing an excitonic splitting similar to that obtained for QT is reported. All other substituted oligothiophenes presented show a conformational change, following the aggregation process. This difference is explained by more disordered crystalline forms for DMOQT and DDQT. Theoretical calculations using the ZINDO/S semiempirical method are also performed on the crystalline structure of each derivative in an attempt to correlate the optical properties of these molecules in their aggregated forms and in the solid state with the molecular arrangement found in the crystal.

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Section: Resultssupporting

confidence: 76%

Section: Introductionmentioning

confidence: 97%

Intermolecular Interactions in Conjugated Oligothiophenes. 3. Optical and Photophysical Properties of Quaterthiophene and Substituted Quaterthiophenes in Various Environments

et al. 1999

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“…The resultant picosecond PM spectra are dramatically different from those previously measured in thin polycrystalline ␣6T films. 22,23 First, a pronounced short-lived PA band ͑band A͒ is observed at បϭ1.25 eV in the LT crystal and at បϭ1.3 eV in the HT crystal phase. This band is usually not observed in polycrystalline films.…”

Section: A Femtosecond and Picosecond Photomodulationmentioning

confidence: 99%

“…20 Therefore, it is not surprising that the transient PM spectra of ␣6T crystals dramatically differ from those of ␣6T films. 22,23 The ultrafast dynamics in films are governed by exciton trapping at numerous defects, most of which act as deep traps. As a result, it is impossible to measure the intrinsic PM spectrum of free Frenkel excitons.…”

Section: A Femtosecond and Picosecond Photomodulationmentioning

confidence: 99%

“…These traps are similar to those found in polycrystalline films; the main difference is their respective concentra-tions. Alternative assignments are triplet excitons 23 and charge transfer excitons, 22 both of which have been invoked before to describe the PM spectral dynamics in polycrystalline ␣6T films.…”

Section: B Nanosecond and Microsecond Photomodulationmentioning

confidence: 99%

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Excitation dynamics in single molecular crystals of α-hexathiophene from femtoseconds to milliseconds

Фролов¹,

Kloc²,

Batlogg³

et al. 2001

Phys. Rev. B

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We identify odd-and even-parity states and measure transient photomodulation spectra of Frenkel excitons in ␣-hexathiophene single crystals. The lowest Frenkel excitons are characterized by a stimulated emission band at ϳ2 eV and an absorption band at 1.3 eV. Intramolecular internal conversion governs transitions from upper excited states to the lowest exciton and occurs in 200 fs. We observe exciton trapping on the nanosecond time scale; as a result, the millisecond photomodulation spectrum is dominated by the absorption of trap states. Using photoinduced-absorption-detected magnetic resonance spectroscopy, we identify the excited-state absorption spectra of triplet excitons and polarons, both of which are produced with a low quantum yield. The triplet absorption band is structureless and approximately 4 times wider than the absorption of singlet excitons. The long-lived photoexcitations are also studied by the photoluminescence-detected magnetic resonance ͑PLDMR͒ technique, as a function of the magnetic field orientation in the crystal b-c plane. We find that there exist two triplets with similar zero-field-splitting parameters, but with the principal axes oriented along different directions, giving rise to six magnetic resonances in the PLDMR spectra.

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Revealing ultrafast relaxation dynamics in six-thiophene thin film and single crystal

Zhao

Kloc

et al. 2021

Journal of Photochemistry and Photobiology A: Chemistry

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Femtosecond Double-Pulse Excitation Study of α-Sexithienyl Film

Cited by 13 publications

References 30 publications

Intermolecular Interactions in Conjugated Oligothiophenes. 3. Optical and Photophysical Properties of Quaterthiophene and Substituted Quaterthiophenes in Various Environments

Intermolecular Interactions in Conjugated Oligothiophenes. 3. Optical and Photophysical Properties of Quaterthiophene and Substituted Quaterthiophenes in Various Environments

Excitation dynamics in single molecular crystals of α-hexathiophene from femtoseconds to milliseconds

Revealing ultrafast relaxation dynamics in six-thiophene thin film and single crystal

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