Wannier excitons and Franz-Keldysh effect of polydiacetylene chains diluted in their single crystal monomer matrix

Horvath, A.; Weiser, G.; Lapersonne‐Meyer, C.; Schott, M.; Spagnoli, S.

doi:10.1103/physrevb.53.13507

Cited by 75 publications

(67 citation statements)

References 24 publications

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“…Although expected for the Franz-Keldysh e¤ect 24 it has been observed at similar …elds only in semiconductors with small reduced mass like Ge, 25 GaAs 26 and InGaAs 27 but also in fully polymerized DCH 9 and on blue chains in 3BCMU and 4BCMU monomer single crystals. 10 Fieldbroadening leads to a redshift of the …rst peak at 3.10 eV and a blueshift of all peaks above 3.15 eV. The very small shift of the dominant negative peak at 3.12 eV is consistent with the Franz-Keldysh e¤ect.…”

Section: Temperature and …Eld-strength Dependencesupporting

confidence: 61%

“…and 4BCMU. 10 The spectrum at room temperature shows again the thermal broadening and blue shift of the absorption edge.…”

Section: Survey Of Absorption and Electroabsorption Spectramentioning

confidence: 87%

“…The free electron gap is resolved by a pronounced Franz-Keldysh e¤ect although its absorption is hidden under vibronic progressions of a strong exciton which responds to an external …eld by a quadratic Stark shift. 8 The EA spectra yield not only the band gap and an exciton binding energy of about 500 meV but derive from …eld broadening of Franz-Keldysh oscillations a reduced mass of about 0:05m o of blue chains in DCH polymer single crystals 9 and those diluted in monomer single crystals of 3BCMU and 4BCMU, 10 much smaller than the free electron mass m 0 .…”

Section: Introductionmentioning

confidence: 99%

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Stark effect and Franz-Keldysh effect of a quantum wire realized by conjugated polymer chains of a diacetylene 3NPh2

et al. 2010

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Conjugated polymer chains diluted in monomer single crystals of a novel diacetylene, 1,10-bis(diphenylamino)-4,6-decadiyne, represent quantum wires of long range coherence. They di¤er from most polydiacetylenes by their repeat unit that consists of two C 4 units with twisted molecular planes. The resulting modi…cation of exciton and band states is studied by electroabsorption which resolves an increase of the exciton transition energy to 2.399 eV and of the free electron gap to 3.158 eV. The Stark shift of the exciton reveals a signi…cant reduction of the exciton radius by about 40 % to 6 1 Å which is consistent with a similar increase of the exciton binding energy to 759 meV. The lineshape of electroabsorption spectra at the free electron gap is for …elds larger than 30 kV/cm in accordance with the one-dimensional Franz-Keldysh e¤ect and yields a reduced mass of 0.07 m 0 larger than in other PDA. Spectra at smaller …elds are distorted by contributions of a weak dipole allowed and a forbidden exciton 38 and 12 meV, respectively below the bandgap.Coherent coupling of free electrons and vibrational modes leads to replicas of the Franz-Keldysh e¤ect. Since light polarized parallel to the conjugated chain excites two propagating modes in the monomer crystals the quantitative analysis was restricted to EA spectra taken with perpendicular polarization in samples which transmit only the weakly absorbed polariton mode.

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Section: Temperature and …Eld-strength Dependencesupporting

confidence: 61%

“…and 4BCMU. 10 The spectrum at room temperature shows again the thermal broadening and blue shift of the absorption edge.…”

Section: Survey Of Absorption and Electroabsorption Spectramentioning

confidence: 87%

Section: Introductionmentioning

confidence: 99%

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Stark effect and Franz-Keldysh effect of a quantum wire realized by conjugated polymer chains of a diacetylene 3NPh2

et al. 2010

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“…The limiting case of through-bond, intrachain excitonic coupling leads to what can be considered as Wannier-Mott excitons in one-dimensional lattices. 26,27 In such excitons, the electron and hole are bound over several unit cells. A compelling example of this limit is provided by isolated, extended chains of red-phase polydiacetylene derivatives, 27 which show ultra narrow photoluminescence linewidths and superradiance [28][29][30] characteristic of J-aggregates at low temperature.…”

mentioning

confidence: 99%

“…26,27 In such excitons, the electron and hole are bound over several unit cells. A compelling example of this limit is provided by isolated, extended chains of red-phase polydiacetylene derivatives, 27 which show ultra narrow photoluminescence linewidths and superradiance [28][29][30] characteristic of J-aggregates at low temperature. 31 The work by Niles et al 1 therefore demonstrates that in regioregular P3HT films, there is a competition between J-like (intrachain) and H-like (interchain) excitonic coupling.…”

mentioning

confidence: 99%

Two-dimensional spatial coherence of excitons in semicrystalline polymeric semiconductors: Effect of molecular weight

et al. 2013

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The electronic properties of macromolecular semiconductor thin films depend profoundly on their solid-state microstructure, which in turn is governed, among other things, by the processing conditions selected and the polymer's chemical nature and molecular weight. Specifically, lowmolecular-weight materials form crystalline domains of cofacially π-stacked molecules, while the usually entangled nature of higher molecular-weight polymers leads to microstructures comprised of molecularly ordered crystallites interconnected by amorphous regions. Here, we examine the interplay between extended exciton states delocalized along the polymer backbones and across polymer chains within the π-stack, depending on the structural development with molecular weight.Such two-dimensional excitations can be considered as Frenkel excitons in the limit of weak intersite coupling. We combine optical spectroscopies, thermal probes, and theoretical modeling, focusing on neat poly(3-hexylthiophene) (P3HT) -one of the most extensively studied polymer semiconductors -of weight-average molecular weight (M w ) of 3-450 kg/mol. In thin-film structures of high-molecular-weight materials (M w > 50 kg/mol), a balance of intramolecular and intermolecular excitonic coupling results in high exciton coherence lengths along chains (~4 thiophene units), with interchain coherence limited to ~2.5 chains. In contrast, for structures of low-M w P3HT (<40 kg/mol), the interchain exciton coherence is dominant (~20% higher than in architectures formed by high-molecular-weight materials). In addition, the spatial coherence within the chain is significantly reduced (by nearly 30%). These observations give valuable structural information; they suggest that the macromolecules in aggregated regions of high-molecular-weight P3HT adopt a more planar conformation compared to low-molecular-weight materials. This results in the observed increase in intrachain exciton coherence. In contrast, shorter chains seem to lead to torsionally more disordered architectures. A rigorous, fundamental description of primary photoexcitations in π-conjugated polymers is hence developed: two-dimensional excitons are defined by the chain-length dependent molecular arrangement and interconnectivity of the conjugated macromolecules, leading to interplay between intramolecular and intermolecular spatial coherence.

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Optical Properties of Excitons in Low Dimensional Systems

Czajkowski

Bassani²

1998

phys. stat. sol. (a)

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Wannier excitons and Franz-Keldysh effect of polydiacetylene chains diluted in their single crystal monomer matrix

Cited by 75 publications

References 24 publications

Stark effect and Franz-Keldysh effect of a quantum wire realized by conjugated polymer chains of a diacetylene 3NPh2

Stark effect and Franz-Keldysh effect of a quantum wire realized by conjugated polymer chains of a diacetylene 3NPh2

Two-dimensional spatial coherence of excitons in semicrystalline polymeric semiconductors: Effect of molecular weight

Optical Properties of Excitons in Low Dimensional Systems

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