Anion and cation absorption spectra of conjugated oligomers and polymers

Deussen, M.; Bäßler, H.

doi:10.1016/0301-0104(92)87148-3

Cited by 63 publications

(60 citation statements)

References 34 publications

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“…3(a)). The transient absorption spectrum is , and is a similar to that previously reported for the radical cations of various p-phenylenevinylene oligomers obtained by chemical oxidation [42,44]. Theoretical studies on the positive charge carrier (polaron) state of oligo(phenylenevinylenes) [47] suggest that they should show two subgap electronic transitions.…”

Section: Positive Charge Carrierssupporting

confidence: 61%

“…The one-electron reduced species of a number of conjugated oligomers and polymers have been prepared by chemical reduction using alkali metals [42,44,48,49], and have helped assign their negative charge carriers. However, these systems are susceptible to both ion pair formation [50,51] and dimerization of the negative species [52], which will affect both their spectral and chemical properties.…”

Section: Negative Charge Carriersmentioning

confidence: 99%

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Transient absorption spectra of triplet states and charge carriers of conjugated polymers

Miguel

Monkman

Hamblett

et al. 2001

Journal of Molecular Structure

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The use of pulse radiolysis to study transient species in conjugated polymers in solutions is discussed, with particular reference to poly(2-methoxy-5-(2 0 -ethylhexoxy)-p-phenylenevinylene) (MEH-PPV). The excited triplet state is speci®cally generated by energy transfer on radiolysis of benzene solutions in the presence of suitable sensitisers, and its spectrum is reported. The presence of vibronic structure suggests a localised triplet state. By varying the energy of the sensitiser, it is possible to determine the energy of the lowest triplet state. Results are also presented for the triplet±triplet absorptions and energies of ®ve other common p-conjugated polymers. The MEH-PPV triplet absorption, produced on radiolysis, does not increase linearly with either polymer concentration or radiation dose. This is suggested to be due to the presence of multiple triplet excitations on the isolated polymer chains. Intrachain triplet±triplet annihilation is observed, and is seen to lead to delayed¯uorescence. Spectra are also reported for the positive and negative charge carriers of MEH-PPV and the other polymers speci®cally produced by pulse radiolysis of the polymers in chloroform or tetrahydrofuran solutions. q

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Section: Positive Charge Carrierssupporting

confidence: 61%

Section: Negative Charge Carriersmentioning

confidence: 99%

Transient absorption spectra of triplet states and charge carriers of conjugated polymers

Miguel

Monkman

Hamblett

et al. 2001

Journal of Molecular Structure

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“…We have determined the energetic position of the polaron absorption bands in the infrared by chemical doping with the oxidizing dopant SbCl 5 and quantum-chemical calculations 32,33 . SbCl 5 is known to be a strong oxidizing agent and to generate a hole-polaron in the ground state of most conjugated polymers 34,35 . Figure 2i-l shows the corresponding dopant induced variation in the optical density spectra (solid curves), measured by adding a small amount of SbCl 5 (4% weight) to the respective polymers.…”

Section: Lowmentioning

confidence: 99%

Structural correlations in the generation of polaron pairs in low-bandgap polymers for photovoltaics

et al. 2012

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Polymeric semiconductors are materials where unique optical and electronic properties often originate from a tailored chemical structure. This allows for synthesizing conjugated macromolecules with ad hoc functionalities for organic electronics. In photovoltaics, donoracceptor co-polymers, with moieties of different electron affinity alternating on the chain, have attracted considerable interest. The low bandgap offers optimal light-harvesting characteristics and has inspired work towards record power conversion efficiencies. Here we show for the first time how the chemical structure of donor and acceptor moieties controls the photogeneration of polaron pairs. We show that co-polymers with strong acceptors show large yields of polaron pair formation up to 24% of the initial photoexcitations as compared with a homopolymer (η = 8%). π-conjugated spacers, separating the donor and acceptor centre of masses, have the beneficial role of increasing the recombination time. The results provide useful input into the understanding of polaron pair photogeneration in low-bandgap co-polymers for photovoltaics.

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“…The addition of a strong oxidizing (or reducing) agent to semiconducting polymers in solution has been used to investigate the optical spectra and character of the doped polymer [33,35]. As these DPP-based polymers are employed as donor materials and hole transporters in organic solar cells, we are most interested in the spectral signal of the hole polaron (positive free charge carrier).…”

Section: Chemical Dopingmentioning

confidence: 99%

“…The influence of the charge localization on the D and A blocks can promote intra-molecular charge separation, which could benefit charge generation in organic solar cells [20,33,34]. Chemical doping [33,35], electrochemical doping [36], and photoinduced absorption [37] have all proven useful in the investigation and characterization of the nature of charged species and photoexcited states in organic semiconductors. In this work we present results of chemical doping, electrochemical doping and photoinduced absorption studies on PDPP-FPF, PDPP-FNF, PDPP-FAF, and PDPP-TNT.…”

Section: Introductionmentioning

confidence: 99%

Optical Characterization of the Hole Polaron in a Series of Diketopyrrolopyrrole Polymers Used for Organic Photovoltaics

et al. 2014

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A strategy that is often used for designing low band gap polymers involves the incorporation of electron-rich (donor) and electron-deficient (acceptor) conjugated segments within the polymer backbone. In this paper we investigate such a series of Diketopyrrolopyrrole (DPP)-based co-polymers. The co-polymers consisted of a DPP unit attached to a phenylene, naphthalene, or anthracene unit. Additionally, polymers utilizing either the thiophene-flanked DPP or the furan-flanked DPP units paired with the naphthalene comonomer were compared. As these polymers have been used as donor materials and subsequent hole transporting materials in organic solar cells, we are specifically interested in characterizing the optical absorption of the hole polaron of these DPP based copolymers. We employ chemical doping, electrochemical doping, and photoinduced OPEN ACCESSPolymers 2015, 7 70 absorption (PIA) studies to probe the hole polaron absorption spectra. While some donor-acceptor polymers have shown an appreciable capacity to generate free charge carriers upon photoexcitation, no polaron signal was observed in the PIA spectrum of the polymers in this study. The relations between molecular structure and optical properties are discussed.

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Anion and cation absorption spectra of conjugated oligomers and polymers

Cited by 63 publications

References 34 publications

Transient absorption spectra of triplet states and charge carriers of conjugated polymers

Transient absorption spectra of triplet states and charge carriers of conjugated polymers

Structural correlations in the generation of polaron pairs in low-bandgap polymers for photovoltaics

Optical Characterization of the Hole Polaron in a Series of Diketopyrrolopyrrole Polymers Used for Organic Photovoltaics

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