Absorption and emission in oligo-phenylene vinylene nanoaggregates: The role of disorder and structural defects

Spano, Frank C.

doi:10.1063/1.1446034

Cited by 165 publications

(238 citation statements)

References 60 publications

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“…1b is the experimental linear absorption spectrum of the dimer (solid curve), which in turn is determined by the total contribution of collective excited states. The linear absorption measurements of both the monomer and dimer are well reproduced using the vibronic exciton model as formulated by the Holstein Hamiltonian [29], which is evaluated using the two-particle approximation [32,33] (details given in Supplementary Section 2). The best agreement between calculations and experiments is found using an excitonic coupling strength of 800 cm −1 , while the vibronic coupling is described using a vibrational frequency From the calculated stick spectrum, shown in Fig.…”

Section: Vibronic Excitons Of a Cyanine Dimermentioning

confidence: 99%

Laser-Limited Signatures of Quantum Coherence

et al. 2015

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The observation of persistent oscillatory signals in multidimensional spectra of proteinpigment complexes has spurred a debate on the role of coherence-assisted electronic energy transfer as a key operating principle in photosynthesis. Vibronic coupling has recently been proposed as an explanation for the long lifetime of the observed spectral beatings. However, photosynthetic systems are inherently complicated, and tractable studies on simple molecular compounds are in demand to fully understand the underlying physics. In this work, we present measurements and calculations on a solvated molecular homodimer with clearly resolvable oscillations in the corresponding twodimensional spectra. Through analysis of the various contributions to the nonlinear response, we succeed in isolating the signal due to inter-exciton coherence. We find that while calculations predict a prolongation of this coherence due to vibronic coupling, the combination of dynamic disorder and vibrational relaxation leads to a coherence decay on a timescale comparable to the electronic dephasing time.

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Section: Vibronic Excitons Of a Cyanine Dimermentioning

confidence: 99%

Laser-Limited Signatures of Quantum Coherence

et al. 2015

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“…34,39,40 One way to appreciate the differences in the circular polarization dissymmetry as a function of exciton bandwidth is to rewrite the emitting exciton in the exciton-phonon basis set up to terms containing zero and one phonon. We obtain…”

Section: Weak and Strong Field Comparisonmentioning

confidence: 99%

“…34 Larger excitonic couplings require three and higher particle states, primarily for attaining accurate spectral properties of the low ͑high͒ energy excitons in aggregates with J 0 Ͼ0 (J 0 Ͻ0). For this work we investigate aggregates with J 0 as large as 10 0 , requiring up to three-particle excitations.…”

Section: Aggregate Emissionmentioning

confidence: 99%

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Analysis of the vibronic fine structure in circularly polarized emission spectra from chiral molecular aggregates

Spano

Zhen

Meskers

2004

The Journal of Chemical Physics

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Using a Frenkel-exciton model, the degree of circular polarization of the luminescence (g lum ) from one-dimensional, helical aggregates of chromophoric molecules is investigated theoretically. The coupling between the electronic excitation and a local, intramolecular vibrational mode is taken into account. Analytical expressions for the fluorescence band shape and g lum are presented for the case of strong and weak electronic coupling between the chromophoric units. Results are compared to those from numerical calculations obtained using the three particle approximation. g lum for the 0-0 vibronic band is found to be independent of the relative strength of electronic coupling between chromophores and excitation-vibration coupling. It depends solely on the number of coherently coupled molecules. In contrast, for the higher vibronic transitions ͉g lum ͉ decreases with decreasing strength of the electronic coupling. In the limit of strong electronic coupling, ͉g lum ͉ is almost constant throughout the series of vibronic transitions but for weak coupling ͉g lum ͉ becomes vanishingly small for all vibronic transitions except for the 0-0 transition. The results are interpreted in terms of dynamic localization of the excitation during the zero point vibrational motion in the excited state of the aggregate. It is concluded that circular polarization measurements provide an independent way to determine the coherence size and bandwidth of the lowest exciton state for chiral aggregates.

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“…1(c). This second result can be quantified by means of the Huang-Rhys factor (S), defined as the intensity ratio between the 1-0 ( 660) and 0-0 ( 610 nm) emission bands [18]. This factor provides a direct measure for the coupling of the excited state and a certain molecular vibration.…”

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confidence: 99%

Effect of Disorder on Ultrafast Exciton Dynamics Probed by Single Molecule Spectroscopy

et al. 2006

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We present a single-molecule study unraveling the effect of static disorder on the vibrational-assisted ultrafast exciton dynamics in multichromophoric systems. For every single complex, we probe the initial exciton relaxation process by an ultrafast pump-probe approach and the coupling to vibrational modes by emission spectra, while fluorescence lifetime analysis measures the amount of static disorder. Exploiting the wide range of disorder found from complex to complex, we demonstrate that static disorder accelerates the dephasing and energy relaxation rate of the exciton. DOI: 10.1103/PhysRevLett.97.216403 PACS numbers: 71.35.Aa, 32.50.+d, 78.47.+p For many decades assemblies of coupled emitters have been studied intensively due to their intriguing properties of spectral narrowing [1] and enhancement of spontaneous emission rate (superradiance) [2]. This behavior stems from coherent excited state energy (exciton) delocalization over the aggregate [3,4]. The exploitation of exciton delocalization for a controlled transfer of energy in photonics and electronics devices as well as in novel schemes for quantum computation has sparked new interest in a wide variety of multichromophoric assemblies, such as photonic polymers [5], light harvesting complexes [6], and quantum dot arrays [7]. In practice, the performance of these systems depends on the extent of coherent exciton delocalization, a property varying in time and space due to static and dynamic disorder [8,9]. Understanding how these two parameters constrain the extent of collective excited states in multichromophoric assemblies is therefore a crucial step in the design of functional excitonically based molecular devices.Static disorder in dye assemblies mainly arises from differences in the energy of the interacting chromophores. The initial exciton created upon absorption is then confined to a region smaller than the actual size of the complex [10]. Coupling of this state to molecular vibrations and bath phonon modes (dynamic disorder) leads to subsequent ultrafast dephasing and energy relaxation through the exciton band. As a consequence, the coherence size of the exciton is further reduced [11]. Therefore, the properties of the final thermalized exciton result from the action of both static and dynamic disorder. The combined effects of these parameters on exciton dynamics have been studied so far theoretically [12] and by means of bulk spectroscopy [13]. In bulk experiments, however, the interplay of static and dynamic disorder cannot be disentangled since the average over a wide range of energy differences from molecule to molecule is measured.In this Letter we investigate the effect of static disorder on exciton dynamics in a multichromophoric system using a unique combination of several room-temperature singlemolecule spectroscopy (SMS) techniques. The coherent delocalization length of the final thermalized exciton is probed using steady-state and fast SMS methods, thus unraveling the extent of static disorder in individual aggregates. The interpla...

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Absorption and emission in oligo-phenylene vinylene nanoaggregates: The role of disorder and structural defects

Cited by 165 publications

References 60 publications

Laser-Limited Signatures of Quantum Coherence

Laser-Limited Signatures of Quantum Coherence

Analysis of the vibronic fine structure in circularly polarized emission spectra from chiral molecular aggregates

Effect of Disorder on Ultrafast Exciton Dynamics Probed by Single Molecule Spectroscopy

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