The Raman spectra of methyl substituted ladder type poly(p-phenylene)

Somitsch, D.; Wenzl, Franz P.; Kreith, Josef; Pressl, M.; Kaindl, Reinhard; Scherf, Ullrich; Leising, G.; Knöll, P.

doi:10.1016/s0379-6779(02)01266-3

Cited by 9 publications

(7 citation statements)

References 13 publications

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“…As pointed out above a CC stretching mode around 1600 cm −1 is usually found in addition to several other less intense modes depending on the symmetry and complexity of the molecule as shown for two conjugated polymers (MeLPPP and PFO, Figure b,c) without any additional heteroatoms (e.g., sulfur). The prominent Raman mode of MeLPPP at 1322 cm −1 (0.164 eV) is related to asymmetric stretching and compressing of the CC bonds and matches the first peak of the vibronic progression in the absorption and emission spectrum of MeLPPP (see Figure b) . The D‐ and G‐modes of the (6,5) nanotubes play a similar role for the phonon sideband in Figure a.…”

Section: Optical and Electronic Propertiessupporting

confidence: 56%

Semiconducting Single‐Walled Carbon Nanotubes or Very Rigid Conjugated Polymers: A Comparison

Zaumseil

2018

Adv Elect Materials

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With the ability to produce large amounts of purely semiconducting and even monochiral dispersions of single-walled carbon nanotubes (SWCNT) their application as a bulk material in thin film devices on a large scale becomes feasible. Their physical properties, processing, and final devices are quite similar to those of semiconducting polymers. In the extreme case one may view carbon nanotubes as very long, rigid, and fully conjugated polymers. This analogy raises the question whether the knowledge accumulated over the last two decades of processing and studying conjugated polymers could be transferred to solution-processed nanotube devices. Here, the optical and electronic properties of both materials in solution and in thin films are discussed and compared with a focus on their application in optoelectronic devices. Some striking similarities and common issues are highlighted to show the connection between conjugated polymers and SWCNTs as 1D semiconductors.

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Section: Optical and Electronic Propertiessupporting

confidence: 56%

Semiconducting Single‐Walled Carbon Nanotubes or Very Rigid Conjugated Polymers: A Comparison

Zaumseil

2018

Adv Elect Materials

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“…Here, the electronic transition appears as most intense line at 21 370 cm –1 . This line is accompanied by two very weak transitions at smaller energies of 1300 and 1560 cm –1 , which are assigned to (inter-ring and aromatic ring) carbon-bond stretch modes. , These vibrational lines possess a smaller intensity with respect to the corresponding modes (iii) and (iv) in the single-dimer spectrum. For MeLPPP intramolecular vibrational modes with energies below 1000 cm –1 are not visible in our data.…”

Section: Resultsmentioning

confidence: 94%

“…These vibrations are ascribed to carbon-bond stretch modes based on Raman spectra and quantum chemical calculations. 20,48,49 In the MeLPPP single-molecule spectra the intensities of these vibrational lines, relative to the corresponding ZPL intensities, are typically weaker as compared to the situation in the singledimer spectra. This observation is in line with the trend in the ensemble spectra (Figure 1a,b and Figure S1).…”

Section: ■ Resultsmentioning

confidence: 98%

Influence of the Conjugation Length on the Optical Spectra of Single Ladder-Type (p-Phenylene) Dimers and Polymers

et al. 2016

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We employ low-temperature single-molecule photoluminescence spectroscopy on a π-conjugated ladder-type (p-phenylene) dimer and the corresponding polymer methyl-substituted ladder-type poly(p-phenylene), MeLPPP, to study the impact of the conjugation length (π-electron delocalization) on their optical properties on a molecular scale. Our data show that the linear electron-phonon coupling to intramolecular vibrational modes is very sensitive to the conjugation length, a well-known behavior of organic (macro-) molecules. In particular, the photoluminescence spectra of single dimers feature a rather strong low-energy (150 cm(-1)) skeletal mode of the backbone, which does not appear in the spectra of individual chromophores on single MeLPPP chains. We attribute this finding to a strongly reduced electron-phonon coupling strength and/or vibrational energy of this mode for MeLPPP with its more delocalized π-electron system as compared to the dimer. In contrast, the line widths of the purely electronic zero-phonon lines (ZPL) in single-molecule spectra do not show differences between the dimer and MeLPPP; for both systems the ZPLs are apparently broadened by fast unresolved spectral diffusion. Finally, we demonstrate that the low-temperature ensemble photoluminescence spectrum of the dimer cannot be reproduced by the distribution of spectral positions of the ZPLs. The dimer's bulk spectrum is rather apparently broadened by electron-phonon coupling to the low-energy skeletal mode, whereas for MeLPPP the inhomogeneous bulk line shape resembles the distribution of spectral positions of the ZPLs of single chromophores.

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“…It is not possible to resolve which vibronic modes contribute to the HExEm as the vibronic manifold is complex with many overtones from low-energy modes. 41,51 Whereas the weak HExEm suggests a tiny fraction of N λ on the S 1 v 1,j states recombine directly, the bulk relaxes to the S 1 v 0,j states during the first ∼1.0 ps immediately after t 0 .…”

Section: Exclusion Of Rrsmentioning

confidence: 99%

Femtosecond hot-exciton emission in a ladder-typeπ-conjugated rigid-polymer nanowire

Dai¹,

Monkman²

2013

Phys. Rev. B

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Publisher's copyright statement:Reprinted with permission from the American Physical Society: Phys. Rev. B 87, 045308 c (2013) by the American Physical Society. Readers may view, browse, and/or download material for temporary copying purposes only, provided these uses are for noncommercial personal purposes. Except as provided by law, this material may not be further reproduced, distributed, transmitted, modied, adapted, performed, displayed, published, or sold in whole or part, without prior written permission from the American Physical Society.Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. A hot exciton is usually the initial elementary excitation product of the solid phase, particularly in lowdimensional photonic materials, which is a bottleneck to all subsequent processes. Measurement of hot-exciton emission (HExEm) is a great challenge due to fast E K relaxation and thus very weak transient emission. Here, we report the unambiguous observation of femtosecond HExEm from thin films of a model quasi-one-dimensional π -conjugated organic rigid-rod quantum nanowire, methyl-substituted ladder-type poly(para-phenylenes), using femtosecond time-resolved fluorescence spectroscopy. The results show clear HExEm from the cooling hot excitons, having a lifetime of ∼500 to ∼800 fs, and concomitant very weak density-dependent singlet-singlet annihilation (SSA) due to this ultrashort dwell time. The ultrafast dispersive migration of the relaxing excitons toward the bottom of the density of states occurs immediately after HExEm, which is simultaneous to the strong density-dependent SSA effect enhanced by the lengthening dwell time.

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The Raman spectra of methyl substituted ladder type poly(p-phenylene)

Cited by 9 publications

References 13 publications

Semiconducting Single‐Walled Carbon Nanotubes or Very Rigid Conjugated Polymers: A Comparison

Semiconducting Single‐Walled Carbon Nanotubes or Very Rigid Conjugated Polymers: A Comparison

Influence of the Conjugation Length on the Optical Spectra of Single Ladder-Type (p-Phenylene) Dimers and Polymers

Femtosecond hot-exciton emission in a ladder-typeπ-conjugated rigid-polymer nanowire

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