Design of novel donor-acceptor polymers with low bandgaps

Bakhshi, A.K.; Yamaguchi, Yoichi; Ago, Hiroki; Yamabe, Tokio

doi:10.1016/0379-6779(96)80178-0

Cited by 25 publications

(28 citation statements)

References 15 publications

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“…The small band gap of poly-1 was also discussed in terms of alternating donor-acceptor moieties. 8,9 According to this interpretation, the small band gap is due to the different positions of HOMO and LUMO in donors and acceptors. The final band gap would then result as the energy difference between the high-lying HOMO of the donor and the low-lying LUMO of the acceptor.…”

Section: Introductionmentioning

confidence: 99%

Theoretical Analysis of Effects of π-Conjugating Substituents on Building Blocks for Conducting Polymers

et al. 1999

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Geometries of 4-dicyanomethylene-4H-cyclopenta[2,1-b:3,4-b′] dithiophene 1 and its CdO, CdS, CdCH 2 , CdCF 2 , and CdC(SR) 2 analogues were optimized using density functional theory. Three of the above groups, CdC(CN) 2 , CdO, and CdS, were also examined on dipyrrole, difuran, dicyclopentadiene, and diborole. Electronic structures were analyzed with respect to their suitability as building blocks for conducting polymers with the natural bond orbital (NBO) method. All bridging groups investigated decrease HOMO-LUMO gaps compared to the unsubstituted parent dimers. Substitution affects HOMO and LUMO energies. Energy gap reduction is caused by a stronger decrease of LUMO energies compared to HOMO energies. The CdS group leads to even smaller energy gaps than the dicyanomethylene group since the HOMO is lowered less in energy with CdS. Compared to unsubstituted dimers, the strongest substituent effects are found with pyrroles and furans. Boroles and thiophenes are least affected. The smallest HOMO-LUMO gaps are obtained for electron-poor systems such as boroles followed by cyclopentadienes. This is analogous to the trend for the unsubstituted parent systems. All of the bridging groups are potential π-acceptors due to their low-lying π*-orbitals, and the corresponding polymers are predicted to be n-dopable. In aromatic structures, the LUMO is localized around the bridging substituent and the coefficients at the R-carbon atoms that reflect electron density are small. This might contribute to the poor conductivity of the n-doped form of poly-1. Electron-poor monomers and polymers tend to switch to quinoid structures. In quinoid repeat units, the HOMO is localized but not as strongly as the LUMO in the aromatic repeat units. The LUMO in quinoid repeat units is delocalized with large coefficients at the R-carbon atoms. Quinoid polymers could therefore be good conductors in the n-doped state.

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Section: Introductionmentioning

confidence: 99%

Theoretical Analysis of Effects of π-Conjugating Substituents on Building Blocks for Conducting Polymers

et al. 1999

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“…[8][9][10][11][12][13][14][15]5,16,17] One of those is to attach bridging groups with low lying π*-orbitals to cis-dithiophene. The polymer of 4-dicyanomethylene-4H-cyclopenta[2,1-b:3,4-b'] dithiophene 1 has a band gap of 0.8 eV, 1 eV smaller than that of polythiophene, and is reversibly n-dopable.…”

Section: Introductionmentioning

confidence: 99%

Electronic Structure Analysis of a New Quinoid Conjugated Polymer

Salzner

2000

J Mol Model

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The low lying unoccupied orbitals of oligomers of 4-dicyanomethylene-4H-cyclopenta[2,1-b:3,4-b'] dithiophene (CDM) are not delocalized over the whole molecule. Is such electron localization in the conduction band of poly-CDM responsible for its low n-type conductivity? Are polymers of the tricyclic thioketone (TCT) with more delocalized unoccupied orbitals a better alternative for stable ndopable conducting polymers? Monomer through tetramer of TCT have been optimized with density functional theory. IP, EA, energy gap, and band width of the corresponding polymer were obtained by extrapolation. Comparison with data for oligomers of 4-dicyanomethylene-4H-cyclopenta [2,1-b:3,4-b'] dithiophene and of thiophene indicates that the novel polymer would have a small band gap and would fulfil the conditions for ndopability and high mobility of n-type carriers.

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“…Synthesis of 3,7-Bis-(4-hexyl-thiophen-2-yl)-dibenzothiophene S,S-dioxide (THSO 2 ) A mixture of 3,7-dibromo-dibenzothiophene S,S-dioxide (0.2 mmol), tributyl-(4-hexyl-thiophen-2-yl)-stannane (0.7 mmol), PdCl 2 (PPh 3 ) 2 (50 mg), and THF (15 mL) were refluxed for 24 h. The solvent was evaporated and the crude product was purified by flash chromatography and the title compound as a yellow solid (47% yield) was achieved (Scheme 1). 1 …”

Section: Equipmentsmentioning

confidence: 97%

“…Furthermore the residue was washed with acetone (to remove unreacted monomer) and dried under vacuum to give PTHSO 2 as orange solid. 1 2.6. Synthesis of copolymers (P(THSO 2 -HTh)) THSO 2 (50 mg) was dissolved in 5 ml of DCM and 5 lL of 3-hexylthiophene (HTh) were introduced into the electrolysis cell containing TBAPF 6 (Scheme 2).…”

Section: Chemical Polymerization Of Thsomentioning

confidence: 99%

“…Conjugated polymers, which are constructed by regular alternation of electron donor (D) and acceptor (A) units are of recent focus of research, since the optical and electronic properties of these polymers could be tailored depending on the type of D and A moieties [1]. Through this approach the polymer's valence and conduction band energy levels could be adjusted according to the highest occupied molecular orbital of the donor and lowest unoccupied molecular orbital of the acceptor moieties [2].…”

Section: Introductionmentioning

confidence: 99%

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