Photogeneration of confined soliton pairs (bipolarons) in polythiophene

Vardeny, Z. Valy; Ehrenfreund, E.; Brafman, O.; Nowak, Michael J.; Schäffer, H.; Heeger, Alan J.; Wudl, Fred

doi:10.1103/physrevlett.56.671

Cited by 246 publications

(40 citation statements)

References 21 publications

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“…This relaxation results in the appearance of new optical transitions in the absorption spectrum at energies beneath the maintransition upon charge injection. These transitions have been detected experimentally [6][7][8][9][10][11][12][13][14] and are in good agreement 15 with the quantum chemical calculations of Cornil et al [16][17][18][19] performed on isolated oligomers ͑see Fig. 2͒ and earlier tightbinding models of isolated, one-dimensional polymer chains developed by Su, Schrieffer, and Heeger ͑the SSH model͒ ͑Ref.…”

Section: Introductionsupporting

confidence: 84%

Optical spectroscopy of field-induced charge in self-organized high mobility poly(3-hexylthiophene)

et al. 2001

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Charge modulation spectroscopy ͑CMS͒ is an electro-optical spectroscopic technique that allows the charge carriers present in the conducting channels of field-effect transistors ͑FET's͒ to be studied in situ. We use this technique to study the charge carriers present in regio-regular poly͑3-hexylthiophene͒ P3HT that has been shown to exhibit high field-effect mobilities of up to 0.1 cm 2 /Vs, similar to that observed for amorphous silicon. We demonstrate that the CMS spectra of charge carriers in high-mobility regio-regular P3HT FET's are independent of charge density, modulation frequency, and temperature. This is evidence for the presence of a single, intrinsic charge carrier that we identify as a singly charged polaronic species. The spectral features attributed to the charged species show a lack of vibronic structure that is in contrast to the vibronic structure present in the bleaching of the main -* absorption of the neutral chains. The transition energies observed in regio-regular P3HT cannot be understood as an extrapolation of charge-induced transitions in isolated short-chain oligomers to long conjugation lengths. Our results give evidence that interchain coupling in highly ordered P3HT is sufficiently strong so that the charge carriers cannot be considered to be confined to a single chain, rather, they now exhibit quasi-two-dimensional characteristics.

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Section: Introductionsupporting

confidence: 84%

Optical spectroscopy of field-induced charge in self-organized high mobility poly(3-hexylthiophene)

et al. 2001

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“…Steady state photo-induced absorption (PA) using pump-probe technique has been used to study these excited states in the polymer film [24]. Vardeny and co-workers [25][26][27][28] have extensively studied the PA and stimulated emission related to singlet/triplet exciton, polaron and bipolarons in pristine polymer films and solutions. The exciton dynamics in OSCs has been focused to better understand the relaxation processes and dynamics of charge separation (from exciton) to weakly bound charge transfer (CT) state (i.e., CT exciton) at the donor-acceptor interface, and its subsequent dissociation to free charge carriers [29][30][31][32][33][34].…”

Section: Mdmo-ppvmentioning

confidence: 99%

Organic and Excitonic Solar Cells

Zhu

2014

Springer Series in Materials Science

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Bulk heterojunction organic solar cells (OSCs) are an attractive alternative to silicon based solar cells due to low cost solution fabrication processes. The efficiencies and lifetimes of OSCs are not yet high enough for them to be commercially viable, but significant research effort has been devoted to improving the performance of OSCs through materials innovation and new device designs. It is known that the optical absorption in organic solar cells is limited due to the mismatch between the charge transport scale and optical absorption depth. There are two major research approaches aimed at improving the performance of OSCs. One approach is focused on the development of new organic compounds with tailored energy levels in order to increase the efficiency of OSCs through improved spectral response over the long wavelength region. The other is to realize broadband absorption enhancement in OSCs through light trapping effects. After a brief overview of basics of OSCs, the charge transport properties, different approaches including incorporating metal nanoparticles and surface plasmonic structures to enhancethe absorption in OSCs will be discussed. Apart from the encouraging results in achieving high efficiency for OSCs, realizing stabile OSC performance over a long operation lifetime also attracts a significant research effort. A comprehensive study on the degradation mechanisms of OSCs is also presented in the last part of the chapter.

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“…Subsequent studies of steady-state photoinduced absorption in polymers with a nondegenerate ground state such as cis-polyacetylene and polythiophene have continued to shed light on processes in this area [3,4]. Considerable differences have been observed in the photoinduced spectra for polymers with degenerate ground states as compared to polymers with nondegenerate ground states.…”

Section: Introductionmentioning

confidence: 97%

Nonlinear Optical Properties of Polyaniline

et al. 1987

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Polyaniline is a family of polymers whose electronic and optical properties can be controlled through variation of the number of electrons and protons on the polymer chain. For example, the emeraldine base form of the polymer (EB) is insulating while the emeraldine salt form (ES) is metallic. We present here results for photoinduced absorption spectroscopy of the emeraldine base form of polyaniline. Unlike earlier studied polymers, the spectrum of emeraldine base contains both subgap photoinduced bleaching (at 1.8 eV) and photoinduced absorption (at 0.9, 1.4, and 3.0 eV). The existence of the bleaching peak is consistent with a model of optically excited localized molecular excitons in the emeraldine base polymer. The energies of the three photoinduced absorptions peaks and an associated interband bleaching (at energies greater than --3.5 eV) are in agreement with the photogeneration of polaron pairs. Laser intensity studies support that the excitons decay monomolecularly while the polarons decay bimolecularly. Picosecond time-resolved spectroscopy of the exciton decay demonstrates the rapid response of this system.

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Photogeneration of confined soliton pairs (bipolarons) in polythiophene

Cited by 246 publications

References 21 publications

Optical spectroscopy of field-induced charge in self-organized high mobility poly(3-hexylthiophene)

Optical spectroscopy of field-induced charge in self-organized high mobility poly(3-hexylthiophene)

Organic and Excitonic Solar Cells

Nonlinear Optical Properties of Polyaniline

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