Oxidized states of soluble oligothiophenes and polythiophenes

Sato, Masaaki; Hiroi, Masao

doi:10.1016/0032-3861(96)83719-0

Cited by 34 publications

(25 citation statements)

References 22 publications

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“…In Table 1 are summarized spectroscopic data of sexithiophene and related compounds in the literature. [17][18][19][20][21][22][23][24][25] Peak positions of the first set of absorption bands for PSE in dichloroethane (0.78 and 1.58 eV) compare well with those for cation radicals (polarons) of sexithiophene and its derivatives, while energies of the second set (0.93 and 1.78 eV) are in good agreement with those for cation radical p-dimers. As is also seen from Table 1, absorption bands observed temporarily for heavily oxidized PSE solutions (1.12 and 1.26 eV) are ascribable to dications (bipolarons).…”

Section: Discussionmentioning

confidence: 54%

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“…15, we plot the energies normalized to half the energy gap, ⌬, against 1/n, with 1/nϭ0 corresponding to the idealized limit of an infinite polymer chain. The experimental data on nT ϩ is obtained from CMS 28,31 and from chemical doping experiments in solution, 9,48,49 whereas the low-mobility P3HT is obtained from CMS. 28 The theoretically calculated transitions are for polarons in polyacetylene calculated from the FBC model 21 and for nT ϩ from quantum chemical calculations.…”

Section: Discussionmentioning

confidence: 99%

Optical spectroscopy of field-induced charge in self-organized high mobility poly(3-hexylthiophene)

et al. 2001

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Charge modulation spectroscopy ͑CMS͒ is an electro-optical spectroscopic technique that allows the charge carriers present in the conducting channels of field-effect transistors ͑FET's͒ to be studied in situ. We use this technique to study the charge carriers present in regio-regular poly͑3-hexylthiophene͒ P3HT that has been shown to exhibit high field-effect mobilities of up to 0.1 cm 2 /Vs, similar to that observed for amorphous silicon. We demonstrate that the CMS spectra of charge carriers in high-mobility regio-regular P3HT FET's are independent of charge density, modulation frequency, and temperature. This is evidence for the presence of a single, intrinsic charge carrier that we identify as a singly charged polaronic species. The spectral features attributed to the charged species show a lack of vibronic structure that is in contrast to the vibronic structure present in the bleaching of the main -* absorption of the neutral chains. The transition energies observed in regio-regular P3HT cannot be understood as an extrapolation of charge-induced transitions in isolated short-chain oligomers to long conjugation lengths. Our results give evidence that interchain coupling in highly ordered P3HT is sufficiently strong so that the charge carriers cannot be considered to be confined to a single chain, rather, they now exhibit quasi-two-dimensional characteristics.

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“…[9] The oligomers that have been studied in detail up to now have a rather limited conjugation length, [13±18, 27] and far less attention has been paid to longer systems. [19,20,28,29] However, conjugation length is an important parameter in differentiating between the various electronic states. For a short oligomer molecule, there is a limit to the decrease in Coulomb repulsion of two like charges, because they cannot diffuse further apart than the limited length of the conjugated system.…”

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Redox States of Long Oligothiophenes: Two Polarons on a Single Chain

Haare

Havinga

Dongen

et al. 1998

Chemistry A European J

261

309

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A detailed investigation is presented of the redox states of three oligothiophenes (nT) with 6, 9, and 12 thiophene units. While open-shell radical cations (polarons) and closed-shell dications (bipolarons) are usually invoked as the primary redox species in these systems, we have obtained evidence that the dication of the longest oligothiophene (12T) has an electronic structure with two individual polarons. The redox states of 6T, 9T, and 12T have been fully characterized using UV/visible/near-IR and ESR spectroscopy in combination with electrospray mass spectrometry. For 6T and 9T, singleelectron oxidation in dichloromethane produces the corresponding radical cations, which form spinless p dimers at lower temperatures. A second oxidation step forms dications which possess a bipolaronic electronic structure. However, the redox behavior of the longest oligothiophene, 12T, is entirely different. Radical cations of 12T disproportionate into neutral oligomers and dications, except at the lowest oxidation levels. The spectral data for doubly oxidized 12T are incompatible with those expected for a bipolaronic structure but are consistent with the formation of two individual polarons on a single chain; this interpretation is also supported by the results from correlated quantum chemical calculations.

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Oxidized states of soluble oligothiophenes and polythiophenes

Cited by 34 publications

References 22 publications

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Optical spectroscopy of field-induced charge in self-organized high mobility poly(3-hexylthiophene)

Redox States of Long Oligothiophenes: Two Polarons on a Single Chain

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