Emission of a Single Conjugated Polymer Chain Isolated in Its Single Crystal Monomer Matrix

Guillet, Thierry; Berréhar, J.; Grousson, R.; Kovensky, José; Lapersonne‐Meyer, C.; Schott, M.; Voliotis, Valia

doi:10.1103/physrevlett.87.087401

Cited by 55 publications

(69 citation statements)

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“…Our experimental setup also allows to perform imaging spectroscopy of a single chain [10]. When the red chain axis is aligned parallel to the spectrometer entrance slits, one obtains along this direction the spatial extension of the emission, and the µ-PL spectrum perpendicularly.…”

Section: Also At Université Evry Val D'essonne Boulevard F Mitterramentioning

confidence: 99%

Evidence of polariton-induced transparency in a single organic quantum wire

et al. 2006

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The resonant interaction between quasi-one dimensional excitons and photons is investigated. For a single isolated organic quantum wire, embedded in its single crystal monomer matrix, the strong exciton-photon coupling regime is reached. This is evidenced by the suppression of the resonant excitonic absorption arising when the system eigenstate is a polariton. These observations demonstrate that the resonant excitonic absorption in a semiconductor can be understood in terms of a balance between the exciton coherence time and the Rabi period between exciton-like and photon-like states of the polariton.In the 50's Hopfield showed that semiclassical theory is inappropriate to describe photon absorption by a semiconductor [1]. Indeed, an exciton has a defined wave-vector and is then only coupled to a single photon state, the one having the same momentum. The resulting system eigenstate during photoexcitation is a mixed exciton-photon state, a polariton, which does not lead to photon absorption if additional couplings are not taken into account [1].On the other hand, an exciton in a quantum well or wire is coupled to a photon continuum in the emission process. Therefore, the emission probability follows the Fermi Golden rule (FGR), whereas this is not a priori so for the absorption. In fact, as recently shown [2], two regimes can be reached by photoexcitation depending on the number of incident photons: a linear regime where photons are absorbed and a non linear one where absorption does not occur, the semiconductor becoming transparent. In the former, the exciton coherence time (generally governed by interaction with phonons) is much shorter than the exciton-photon interaction time [2], and photons are continuously absorbed following the FGR. In the latter, the system eigenstate is a slightly damped polariton, the exciton-photon interaction time

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Section: Also At Université Evry Val D'essonne Boulevard F Mitterramentioning

confidence: 99%

Evidence of polariton-induced transparency in a single organic quantum wire

et al. 2006

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“…in this study to be the most heterogeneous polymeric material studied to date on the single-chromophore level, with the excitonic single-chromophore picture (36)(37)(38) established for the most ordered polymers such as polyfluorenes (39) (PF), ladder-type poly(para-phenylenes) (40, 41) (LPPP), polydiacetylene (42,43) (PDA), and poly(phenylene-ethynylene) (28) (PPE). On the level of single chromophores, P3HT behaves like other prominent materials, such as poly(phenylene-vinylenes) (41, 44) (PPVs), with the exception of exhibiting giant variability in transition wavelengths spanning almost 200 nm.…”

Section: Significancementioning

confidence: 99%

Unraveling the chromophoric disorder of poly(3-hexylthiophene)

Thiessen

Vogelsang

Adachi

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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The spectral breadth of conjugated polymers gives these materials a clear advantage over other molecular compounds for organic photovoltaic applications and is a key factor in recent efficiencies topping 10%. However, why do excitonic transitions, which are inherently narrow, lead to absorption over such a broad range of wavelengths in the first place? Using single-molecule spectroscopy, we address this fundamental question in a model material, poly(3-hexylthiophene). Narrow zero-phonon lines from single chromophores are found to scatter over 200 nm, an unprecedented inhomogeneous broadening that maps the ensemble. The giant red shift between solution and bulk films arises from energy transfer to the lowest-energy chromophores in collapsed polymer chains that adopt a highly ordered morphology. We propose that the extreme energetic disorder of chromophores is structural in origin. This structural disorder on the single-chromophore level may actually enable the high degree of polymer chain ordering found in bulk films: both structural order and disorder are crucial to materials physics in devices.structure-property relations | conformational disorder | photophysics | organic solar cells D espite half a century of research into organic photovoltaics (1), the promise of versatile paint-on solar-cell modules based on conjugated polymers has prompted a present flurry of activity in the field (2-5). A particular appeal of such excitonic solar cells is that very little material is needed to efficiently absorb light. This is due to the fact that the oscillator strength of primary photoexcitations, electron-hole pairs with binding energies far exceeding kT, is focused in the excitonic transition. The obvious downside is that this concentration also means excitonic transitions are inherently narrow and usually offer only mediocre spectral overlap with the broad solar spectrum. How then can excitonic solar cells be designed with appropriate spectral breadth? Merely introducing energetic disorder in the underlying excitonic material should lead to low-energy traps, impeding charge harvesting.Although the optical and electronic properties of conjugated polymers are not perfectly suited to photovoltaics, their absorption spectra are surprisingly broad despite the excitonic nature of the transitions. Moreover, the diversity in functional characteristics revealed by varying processing conditions has fueled the quest to formulate robust structure-property relationships between the electronic and optical properties and the underlying polymer structure (6-12). Polythiophene derivatives have evolved into one of the chosen workhorse materials for solar-cell research (13,14). Early spectroscopic studies established extraordinary solvatochromic and thermochromic characteristics, which were attributed to large conformational changes in response to the immediate environment (15-17). It is little surprise then that such diversity in device characteristics exists when using these materials (4). Poly(3-hexylthiophene) (P3HT) (structure show...

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“…This work exclusively deals with « red » chains. Disorder is very small, the inhomogeneous broadening of the absorption or emission of an ensemble of red chains being less than 2 meV 11,12 . These chains emit a strong resonance fluorescence around 2.28 eV (at 10 K) and several vibronic replicas which are two or more orders of magnitude weaker.…”

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confidence: 99%

“…The emission is polarized parallel to the chain axis. Microphotoluminescence experiments are possible thanks to high dilution and to the intense and narrow resonance emission, then a single isolated chain can be studied 12 . We have shown, that a single red chain has the characteristic properties of a one dimensional semiconducting quantum wire.…”

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confidence: 99%