Polaron-pair generation in poly(phenylene vinylenes)

Frankevich, E. L.; Lymarev, A. A.; Sokolik, I.; Karasz, Frank E.; Blumstengel, S.; Baughman, Ray H.; Hörhold, H.‐H.

doi:10.1103/physrevb.46.9320

Cited by 328 publications

(236 citation statements)

References 20 publications

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“…This could be a result of enhanced intersystem crossing or transformation of geminate polaron pairs from singlet to triplet spin configurations before recombination. 33 The latter explanation is consistent with a correlation between enhanced polaron and triplet photogeneration. The excited state absorption peak of triplet excitons occurs at a much higher energy for 1,3-PPV ͑1.87 eV͒ than for DOO-PPV ͑1.45 eV͒, but at a slightly lower energy than for trans,trans'-distyrylbenzene ͑1.95 eV͒.…”

Section: Photoexcitation Dynamics and Photogeneration Mechanismssupporting

confidence: 72%

Photophysics of a poly(phenylenevinylene) with alternatingmeta-phenylene andpara-phenylene rings

et al. 2000

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We have investigated the photophysics of the luminescent polymer poly͑1,3-phenylenevinylene-alt-2,5-dioctyloxy-1,4-phenylenevinylene͒ by a variety of optical spectroscopies. The incorporation of alternating meta-phenylene and para-phenylene rings restricts conjugation with respect to poly͑para-phenylenevinylene͒ derivatives. As a consequence, excited states are blueshifted and the nonlinear susceptibility is reduced. Absorption by aggregates, which can be obscured by scattering and interference, is clearly revealed by electroabsorption spectroscopy. The reduced symmetry of 1,3-PPV modifies optical selection rules, resulting in strong overlap of the fluorescence spectrum with excited state absorption by charged polarons.

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Section: Photoexcitation Dynamics and Photogeneration Mechanismssupporting

confidence: 72%

Photophysics of a poly(phenylenevinylene) with alternatingmeta-phenylene andpara-phenylene rings

et al. 2000

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“…Frankevich and co workers [32,33] have shown that lifetimes of pairs of paramagnetic species (such as electrons and holes), which may be in singlet and triplet states, are very sensitive to external magnetic fields within the range of hyperfine interaction. In general, models involving pairs of electrons and holes appear promising since typical magnetic dipole fields between pairs of electrons and holes can be expected to be on the order of 10mT .…”

Section: B Discussion Of Possible Mechanismsmentioning

confidence: 99%

Large magnetoresistance in nonmagneticπ-conjugated semiconductor thin film devices

et al. 2005

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Following the recent discovery of large magnetoresistance at room temperature in polyfluorence sandwich devices, we have performed a comprehensive magnetoresistance study on a set of organic semiconductor sandwich devices made from different pi-conjugated polymers and small molecules. The measurements were performed at different temperatures, ranging from 10K to 300K, and at magnetic fields, B < 100mT . We observed large negative or positive magnetoresistance (up to 10% at 300K and 10mT) depending on material and device operating conditions. We compare the results obtained in devices made from different materials with the goal of providing a comprehensive picture of the experimental data. We discuss our results in the framework of known magnetoresistance mechanisms and find that none of the existing models can explain our results.

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“…This is supposed to occur only after diffusion of the excitons in the polymer, which is usually forming an interpenetrating network of domains with the fullerene 12 . However, several experimental and theoretical studies have suggested that the primary photoexcitations in pristine conjugated polymers are not only excitons but also polaron pairs, the latter being more separated electrons and holes with a weaker Coulomb attraction [13][14][15] . Very recently, it has been reported that polaron pairs, formed within the polymer domains, have a significant role in photovoltaic action and are envisaged to be as important as excitons, provided their yield is substantial [16][17][18] .…”

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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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Polaron-pair generation in poly(phenylene vinylenes)

Cited by 328 publications

References 20 publications

Photophysics of a poly(phenylenevinylene) with alternatingmeta-phenylene andpara-phenylene rings

Photophysics of a poly(phenylenevinylene) with alternatingmeta-phenylene andpara-phenylene rings

Large magnetoresistance in nonmagneticπ-conjugated semiconductor thin film devices

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

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