Highly conducting polyparaphenylene, polypyrrole, and polythiophene chains: An<i>ab initio</i>study of the geometry and electronic-structure modifications upon doping

Brédas, Jean Luc; Thémans, B.; Fripiat, J. J.; André, Jean‐Marie; Chance, R. R.

doi:10.1103/physrevb.29.6761

Cited by 729 publications

(284 citation statements)

References 44 publications

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“…We analysed the evolution of the C-C bond lengths along the PCPDT-BT copolymer strands in the neutral and charged states, as computed in our DFT calculations. As previously shown, the presence of a polaron on a conjugated polymer backbone is accompanied by an evolution from aromatic to quinoid structure 39 . Figure 4a shows the difference between a selection of C-C bond lengths in the Complex-1 configuration and the same bonds in the neutral PCPDT-BT strand.…”

Section: Discussionmentioning

confidence: 67%

How intermolecular geometrical disorder affects the molecular doping of donor–acceptor copolymers

et al. 2015

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Molecular doping of conjugated polymers represents an important strategy for improving organic electronic devices. However, the widely reported low efficiency of doping remains a crucial limitation to obtain high performance. Here we investigate how charge transfer between dopant and donor-acceptor copolymers is affected by the spatial arrangement of the dopant molecule with respect to the copolymer repeat unit. We p-dope a donor-acceptor copolymer and probe its charge-sensitive molecular vibrations in films by infrared spectroscopy. We find that, compared with a related homopolymer, a four times higher dopant/ polymer molar ratio is needed to observe signatures of charges. By DFT methods, we simulate the vibrational spectra, moving the dopant along the copolymer backbone and finding that efficient charge transfer occurs only when the dopant is close to the donor moiety. Our results show that the donor-acceptor structure poses an obstacle to efficient doping, with the acceptor moiety being inactive for p-type doping.

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Section: Discussionmentioning

confidence: 67%

How intermolecular geometrical disorder affects the molecular doping of donor–acceptor copolymers

et al. 2015

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“…In contrast, excitation energies were predicted based on band structure calculations, using energy level differences directly as excitation energies and comparing theoretical results for n-doped polymers directly with experimental results on p-doped polythiophene. 66 As computers have improved dramatically in recent years, longer oligomers can be used now, structures can be fully optimized, and excitation energies can be calculated explicitly with reliable methods. UV-spectroscopic data 11,12 for n-doping of PT are not well resolved.…”

Section: Discussionmentioning

confidence: 99%

Theoretical Investigation of Excited States of Oligothiophene Anions

Alkan

Salzner

2008

J. Phys. Chem. A

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Electron-hole symmetry upon p-and n-doping of conducting organic polymers is rationalized with Hückel theory by the presence of symmetrically located intragap states. Since density functional theory (DFT) predicts very different geometries and energy level diagrams for conjugated π-systems than semiempirical methods, it is an interesting question whether DFT confirms the existence of electron-hole symmetry predicted at the Hückel level. To answer this question, geometries of oligothiophene anions with 5-19 rings were optimized and their UV/vis spectra were calculated with time-dependent DFT. Although DFT does not produce symmetrically placed sub-band energy levels, spectra of cations and anions are almost identical. The similarity in transition energies and oscillator strengths of anions and cations can be explained by the fact that the single sub-band energy level of cations lies above the valence band by the same amount of energy as the single sub-band level of anions lies below the conduction band. This and the resemblance of the energy level spacings in valence bands of cations to those in conduction bands of anions give rise to peaks with equal energies and oscillator strengths.

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“…[49][50][51] In the oligomer studies the issue of bipolaron formation was not addressed and the interpretation of polymer results remains controversial. 8,12,13,16,17,20,22,23,25,[52][53][54][55] Electronic structures of PPy and OPs have been investigated theoretically before; 20,[56][57][58][59][60][61][62][63][64][65][66][67][68][69][70] however, we are not aware of calculations of absorption spectra during the doping process of pyrrole oligomers or polymers. We have recently calculated such spectra for polyenes 71 and OTs.…”

Section: Introductionmentioning

confidence: 99%

Theoretical Modeling of the Doping Process in Polypyrrole by Calculating UV/Vis Absorption Spectra of Neutral and Charged Oligomers

Okur

Salzner

2008

J. Phys. Chem. A

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Changes in absorption spectra during doping of oligopyrroles were investigated with time-dependent density functional theory on optimized structures of neutral, singly, and doubly charged pyrrole oligomers with up to 24 rings. In the absence of counterions, defects are delocalized. Counterions induce localization. For dications two polarons on the same chain are preferred over a bipolaron. Intragap absorptions arise in charged species, no matter whether defects are localized or delocalized. Cations and dications give rise to two sub-band transitions. The cation peaks have lower energies than those of dications. The first excitations of cations have lower oscillator strengths than the second; for dications the second peak is weaker than the first. For very long oligomers, the second sub-band absorption vanishes and a third one appears at higher energy. The behavior of pyrrole oligomers is analogous to that of thiophene oligomers. Theoretical UV spectra for cations and dications of short oligomers (six to eight rings) match experimental spectra of polypyrrole at low and at high doping levels, respectively. The error in the theoretical calculations is about 0.4 eV, slightly larger than for thiophene oligomers at the same level of theory.

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Highly conducting polyparaphenylene, polypyrrole, and polythiophene chains: Anab initiostudy of the geometry and electronic-structure modifications upon doping

Cited by 729 publications

References 44 publications

How intermolecular geometrical disorder affects the molecular doping of donor–acceptor copolymers

How intermolecular geometrical disorder affects the molecular doping of donor–acceptor copolymers

Theoretical Investigation of Excited States of Oligothiophene Anions

Theoretical Modeling of the Doping Process in Polypyrrole by Calculating UV/Vis Absorption Spectra of Neutral and Charged Oligomers

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