Conducting Polymers and Composites

Baleg, Abd Almonam; Masikini, Milua; John, Suru Vivian; Williams, Avril; Jahed, Nazeem; Baker, Priscilla; Iwuoha, Emmanuel I.

doi:10.1007/978-3-319-95987-0_17

Cited by 6 publications

(9 citation statements)

References 289 publications

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“…The effect of g -strain is very small at the X-band EPR used; however, it was taken into account when calculating the spectra. Besides, polarons forming in adjacent polymer chains, starting with some critical concentration, can, in principle, collapse into interchain mobile diamagnetic P mob +• P mob +• or intrachain localized paramagnetic P loc –• P loc +• bipolarons with equal g -factors. , The transition polaron ↔ bipolaron can change the experimental LEPR spectra as well. To separate the contributions of different charge carriers into the sum LEPR spectra and to analyze their changes at different experimental conditions, such spectra should be deconvoluted according to the procedure described earlier. , In Figure , the dashed lines represent the effective LEPR spectra and their spectral contributions due to polarons P PANI +• and P +• stabilized in the PANI and photoinitiated in copolymer matrices, respectively, as well as mobile pairs of polarons and methanofullerene radical anions P mob +• mF mob –• photoinitiated in the copolymer backbone of the samples by white light with T c = 3300 K. This allowed one to obtain separately the main magnetic resonance, electron relaxation, and dynamic parameters for all spins at a wide variation of experimental conditions.…”

Section: Resultsmentioning

confidence: 99%

“…Besides, polarons forming in adjacent polymer chains, starting with some critical concentration, can, in principle, collapse into interchain mobile diamagnetic P mob +• ↔ P mob +• or intrachain localized paramagnetic P loc −• ↔ P loc +• bipolarons with equal g-factors. 67,68 The transition polaron ↔ bipolaron can change the experimental LEPR spectra as well. To separate the contributions of different charge carriers into the sum LEPR spectra and to analyze their changes at different experimental conditions, such spectra should be deconvoluted according to the procedure described earlier.…”

Section: Resultsmentioning

confidence: 99%

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Impact of Spin-Exchange Interaction on Charge Transfer in Dual-Polymer Photovoltaic Composites

et al. 2020

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Magnetic resonance, relaxation, and dynamic parameters of spin-charge carriers photoinitiated in dual-polymer composites formed by narrow-band-gap poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-(bithiophene)] (F8T2), poly[2,7-(9,9-dioctylfluorene)-alt-4,7-bis(thiophen-2-yl)benzo-2,1,3-thiadiazole] (PFO-DBT), and poly[N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT) copolymers modified with [6,6]-phenyl-C61-butanoic acid methyl ester (PC61BM) as a photovoltaic spin subsystem and polyaniline salt doped with para-toluenesulfonic acid (PANI:TSA) as a guest spin subsystem were comparatively studied by the direct light-induced electron paramagnetic resonance (LEPR) spectroscopy in a wide photon energy and temperature range. Irradiation of dual-polymer composites by the photons leads to the formation in its photovoltaic subsystem of polarons and methanofullerene radical anions whose concentration and dynamics are determined by the density and energy of the initiating light photons. A part of such polarons first filled high-energetic spin traps formed in the matrix due to its disordering. A crucial role of exchange interaction between different spin ensembles in the charge excitation, relaxation, and transport in multispin narrow-band-gap composites was demonstrated. These processes were interpreted within the framework of hopping of polarons along copolymer chains of photovoltaic subsystems and their exchange interaction with neighboring spin ensembles. Such an interaction was shown to facilitate the transfer of charges and inhibit their recombination in multispin dual-polymer composites. The distribution of spin density over polymer chains in the dual-polymer composites with the π–π stacked architecture was analyzed in the framework of the density functional theory (DFT). It confirmed the transfer of electron spin density between neighboring polymer chains that made formation more likely of radical pairs in triplet state than in singlet one and inhibited their fast geminate recombination. Spin interactions eliminate the selectivity of these systems to the photon energy, extend the range of optical photons they absorb, and, therefore, increase their efficiency to converse the light energy. Handling electronic properties via intra- and intersubsystem spin interactions in such multispin composites allows one to create on their base more efficient and functional electronic and spintronic elements.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Impact of Spin-Exchange Interaction on Charge Transfer in Dual-Polymer Photovoltaic Composites

et al. 2020

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“…60 To confirm this supposition, it would be important to obtain also respective correlations of magnetic resonant, spin and dynamic parameters of mobile and localized charge carriers with molecular and structural properties of the initial and doped composites, as well as with the exciting photon energy. It should also to analyze a possible formation of localized polaron pairs P loc +• ↔ P loc −• with equal energetic and magnetic resonant parameters 61 as well as diamagnetic bipolarons each potentially dissociating into spin polaron couples, BP 2+ ↔ 2P +• in polymer composite matrices, 62,63 including P3DDT. 64 Some charge carriers captured by spin traps can also be released from the latter when interacting with light photons of a certain energy.…”

Section: Resultsmentioning

confidence: 99%

Light-Induced EPR Study of Polymorphic Acene-Stipulated Transition in P3DDT:PC₆₁BM Composite

2022

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We report the light-induced electron paramagnetic resonance (LEPR) and optics study of spin charge carriers initiated by light photons with the energy of 1.34–4.52 eV in the initial and slightly acene-treated composites of a regioregular poly(3-dodecylthiophene) (P3DDT) with a [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM). Light irradiation leads to the formation in both polymorphs of spin charge carriers, polarons, and methanofullerene radical anions. Magnetic resonance, relaxation, and dynamic parameters of such carriers depend on the energy of exciting light photons as well as on a balance of a chaotically structured polymer α-polymorph with spin traps and a more structured its β-polymorph. The charge carriers, photoinitiated in the α-polymorph, are characterized by an extreme dependence of their main parameters from the energy of exciting photons. The increase in the concentration and stability of both mobile charge carriers were reached upon modification of the initial composite by the simplest conjugated acenes. The greatest effect was registered for the composite, weakly doped by naphthalene molecules. The concentration and other properties of charge carriers photoinitiated in a modified composite were found to correlate with the band structure of the acene introduced. Such an effect was interpreted in favor of a triggerlike polymorphic α–β transition stipulated in the system by planar acene molecules. It leads to an acceleration of spin–lattice relaxation of mobile charge carriers, a decrease in the anisotropic diffusion of polarons between polymer chains, and a slow down of the recombination of charge carriers. This opens horizons to use optimally acene-doped polymers and their composites for the creation of electronic and spintronic devices with spin-photon-assisted parameters.

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“…This allows the conclusion in this and analogous systems of spin tunneling within the framework of the Miller–Abrahams model in parallel with their intrachain hopping, which depends on spin traps and also on their exchange interaction with the nearest spin ensembles. One should, however, take into account a possible initial formation in the composites of pairs of localized oppositely charged polarons P loc +• ↔ P loc –• with equal energy and g -factors and diamagnetic bipolarons which are able to dissociate into spin polaron couples, BP 2+ ↔2 P +• . − The combination of these processes could also initiate the appearance of the above-mentioned term in the temperature dependences obtained.…”

Section: Resultsmentioning

confidence: 99%

“…It should be noted that the appearance occurred only after some time in the dependencies shown in Figure of the bell-like component as in the case of other polymer:fullerene composites. , Assuming the presumption of formation of an equal quantity of positively and negatively charged carriers upon excitons’ dissociation, some reasons for such effect can be proposed. Dissociation of some diamagnetic bipolarons into polaron pairs − and/or formation in composites of pairs of localized oppositely charged polarons P loc +• ↔ P loc –• with equal energy and g -factors are possible . Spin-dependent and trap-controlled reversible transition P loc +• ↔ P mob +• can also provoke such dependence .…”

Section: Resultsmentioning

confidence: 99%

Light-Induced Electron Paramagnetic Resonance Study of Charge Transport in Fullerene and Nonfullerene PBDB-T-Based Solar Cells

et al. 2021

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We present a combined light-induced electron paramagnetic resonance (LEPR) study of photoinitiation, relaxation, and recombination of charge carriers initiated by achromatic/white (with a color temperature of 5000 K) and monochromatic (with a photon energy of 1.34–3.41 eV) light in PBDB-T-based photovoltaic systems with PC61BM, PC71BM, and ITIC-M counterions. Charge carriers, polarons on polymer chains, and respective radical anions excited in disordered composite matrixes first fill spin traps, the number, energy depth, and spatial distribution of which are determined by the structure and crystallinity of bulk heterojunctions. By deconvolution of the effective LEPR spectra, the contributions of immobilized and mobile charge carriers, as well as their main magnetic resonance parameters, were determined separately at a wide variety of experimental conditions. The interaction of spins occupying different energy levels in the bandgap of a polymer semiconductor provokes the extreme photon energy sensitivity of the spin-assisted processes carried out in the polymer composites. The density functional theory calculations of the millimeter-waveband LEPR spectrum allowed the conclusion that polarons photoinitiated in the PBDB-T backbone are delocalized over its 4–5 monomers. Side π–π-stack packaging and S-isomerization of electron acceptors were also found. Predominant nongeminate recombination of charge carriers follows multistep trapping–detrapping spin hopping between sites of polymer layers and is strongly governed by the number, energy depth, and spatial distribution of spin traps. It was shown that all spin-involving processes in composites are spin-assisted and, therefore, are determined by the main magnetic resonance properties of both the spin charge carriers. The stability of charge carriers in a polymer-based composite was demonstrated to increase by more than an order of magnitude in the series of radical anions PC61BM–• → ITIC-M–• → PC71BM–•. A further improvement in the functionality of the composite occurs at its slight 2,5-diphenyloxazole modification. The use of low-dimensional ITIC-M instead of PCBM and/or PPO with extended π-system significantly increases the exchange interaction between the spin charge carriers situated on the adjacent layers of the composite. This blocks intrachain charge diffusion but accelerates its interlayer hopping in the polymer matrix, which increases the efficiency and functionality of the composite.

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Conducting Polymers and Composites

Cited by 6 publications

References 289 publications

Impact of Spin-Exchange Interaction on Charge Transfer in Dual-Polymer Photovoltaic Composites

Impact of Spin-Exchange Interaction on Charge Transfer in Dual-Polymer Photovoltaic Composites

Light-Induced EPR Study of Polymorphic Acene-Stipulated Transition in P3DDT:PC₆₁BM Composite

Light-Induced Electron Paramagnetic Resonance Study of Charge Transport in Fullerene and Nonfullerene PBDB-T-Based Solar Cells

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Conducting Polymers and Composites

Cited by 6 publications

References 289 publications

Impact of Spin-Exchange Interaction on Charge Transfer in Dual-Polymer Photovoltaic Composites

Impact of Spin-Exchange Interaction on Charge Transfer in Dual-Polymer Photovoltaic Composites

Light-Induced EPR Study of Polymorphic Acene-Stipulated Transition in P3DDT:PC61BM Composite

Light-Induced Electron Paramagnetic Resonance Study of Charge Transport in Fullerene and Nonfullerene PBDB-T-Based Solar Cells

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Light-Induced EPR Study of Polymorphic Acene-Stipulated Transition in P3DDT:PC₆₁BM Composite