Coherent exciton transport driven by torsional dynamics: a quantum dynamical study of phenylene-vinylene type conjugated systems

Binder, Robert J.; Wahl, J.; Römer, Sarah; Burghardt, Irène

doi:10.1039/c3fd20148a

Cited by 34 publications

(59 citation statements)

References 75 publications

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“…Furthermore, the inclusion of vibronic couplings and the non‐perturbative treatment of vibronic wavepacket dynamics is of particular importance for the systems under study. In some cases, it is useful to construct PES cuts for the most important vibrational modes . More systematically, spectral densities can be obtained from electronic structure information, using a shifted‐harmonic oscillator approximation .…”

Section: Discussionmentioning

confidence: 99%

“…In line with the treatment of Refs. , a basis of e ‐ h quasi‐particle states is introduced,

| ν_{e} μ_{h} 〉 \equiv | ν μ 〉

, where the electron is located at site

ν_{e} = ν

with position

r_{ν}^{e}

, while the hole is located at site

μ_{h} = μ

with position

r_{μ}^{h}

. All other sites remain in their ground states.…”

Section: Vibronic Lattice Models and High‐dimensional Quantum Dynamicsmentioning

confidence: 99%

“…A generic form of a vibronic coupling Hamiltonian in the e ‐ h basis reads as follows,

\hat{H} ({{\overset{z}{true}}_{i}}) = \sum_{ν μ} \sum_{ν' μ'} {\overset{H}{true}}_{ν μ, ν' μ'} ({{\overset{z}{true}}_{i}}) | ν μ 〉 〈 ν' μ' |

where the Hamiltonian elements

{\overset{H}{true}}_{ν μ, ν' μ'}

are conveniently written as a sum over an electronic part (

{\overset{H}{true}}^{el}

) and an electron‐phonon, or vibronic coupling part (

{\overset{H}{true}}^{e - ph}

{\overset{H}{true}}_{ν μ, ν' μ'} ({{\overset{z}{true}}_{i}}) = {\overset{H}{true}}_{ν μ, ν' μ'}^{el} + {\overset{H}{true}}_{ν μ, ν' μ'}^{e - ph} ({{\overset{z}{true}}_{i}})

where the electronic part is composed of an electronically diagonal on‐site part (

{\overset{H}{true}}^{on - site}

) and an electronically off‐diagonal coupling part (

{\overset{H}{true}}^{coup}

{\overset{H}{true}}_{ν μ, ν' μ'}^{el} = δ_{ν ν'} δ_{μ μ'} {\overset{H}{true}}_{ν μ, ν' μ'}^{on - site}

…”

Section: Vibronic Lattice Models and High‐dimensional Quantum Dynamicsmentioning

confidence: 99%

See 2 more Smart Citations

Quantum dynamical studies of ultrafast charge separation in nanostructured organic polymer materials: Effects of vibronic interactions and molecular packing

Polkehn

Eisenbrandt

Tamura

et al. 2017

Int J of Quantum Chemistry

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We review recent work employing high-dimensional quantum dynamical techniques to study ultrafast charge separation in functional organic materials, in view of understanding the key microscopic factors that lead to efficient charge generation in photovoltaics applications. As highlighted by recent experiments, these processes can be guided by quantum coherence, despite the presence of static and dynamic disorder. The present approach combines first-principles parametrized lattice Hamiltonians, based on Time-Dependent Density Functional Theory (TDDFT) and/or high-level electronic structure calculations, with accurate quantum dynamics simulations using the Multi-Configuration Time-Dependent Hartree (MCTDH) method. This contribution specifically addresses the mechanism of charge generation in (i) regioregular oligothiophene-fullerene aggregates, and (ii) highly ordered oligothiophene-perylene diimide co-oligomer assemblies. These studies highlight that chemical design of donor-acceptor combinations needs to account for the effects of electronic delocalization and the modified energetics due to molecular packing, as well as multiple transfer pathways and internal conversion channels induced by vibronic interactions.excitonic states, molecular packing, organic photovoltaics, quantum dynamics, ultrafast charge separation | I N TR ODU C TI ONIn organic donor-acceptor (DA) materials developed for photovoltaics applications, the break-up of photogenerated excitons at DA heterojunction interfaces initiates the irreversible separation of charge carriers. [1,2] Over the past few years, it has become increasingly clear that the efficiency of this process depends on a complex interplay of different factors, such that design principles based on the engineering of molecular structure and DA band offsets are not necessarily sufficient. Indeed, the photochemical processes inherent to the molecular donor and acceptor materials necessitate a molecular-level analysis that may deviate from the basic picture derived from semiconductor physics. This is underscored by an increasing body of evidence from time-resolved spectroscopies [3][4][5][6][7] showing that the elementary energy and charge transfer (CT) processes in typical photovoltaic materials are often of quantum coherent character. Conventional kinetic descriptions are therefore not apt to render a faithful picture of these elementary steps, and may only be valid on longer time scales where hopping type transport dynamics sets in.Even long-range electron-hole separation under the effect of a Coulomb barrier may not necessarily obey the slow, thermally activated dynamics described by the Onsager-Braun model. [8] Indeed, recent time-resolved experiments, for example, for prototypical blends of poly-3-hexylthiophene (P3HT) and the fullerene derivative [6,6]-phenyl-C 61 butyric acid methyl ester (PCBM) and related systems, report ultrafast longrange charge separation, especially in materials exhibiting regioregular morphologies. [9][10][11][12][13][14][15] To explain these ob...

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Section: Discussionmentioning

confidence: 99%

“…In line with the treatment of Refs. , a basis of e ‐ h quasi‐particle states is introduced,

| ν_{e} μ_{h} 〉 \equiv | ν μ 〉

, where the electron is located at site

ν_{e} = ν

with position

r_{ν}^{e}

, while the hole is located at site

μ_{h} = μ

with position

r_{μ}^{h}

. All other sites remain in their ground states.…”

Section: Vibronic Lattice Models and High‐dimensional Quantum Dynamicsmentioning

confidence: 99%

“…A generic form of a vibronic coupling Hamiltonian in the e ‐ h basis reads as follows,

\hat{H} ({{\overset{z}{true}}_{i}}) = \sum_{ν μ} \sum_{ν' μ'} {\overset{H}{true}}_{ν μ, ν' μ'} ({{\overset{z}{true}}_{i}}) | ν μ 〉 〈 ν' μ' |

where the Hamiltonian elements

{\overset{H}{true}}_{ν μ, ν' μ'}

are conveniently written as a sum over an electronic part (

{\overset{H}{true}}^{el}

) and an electron‐phonon, or vibronic coupling part (

{\overset{H}{true}}^{e - ph}

{\overset{H}{true}}_{ν μ, ν' μ'} ({{\overset{z}{true}}_{i}}) = {\overset{H}{true}}_{ν μ, ν' μ'}^{el} + {\overset{H}{true}}_{ν μ, ν' μ'}^{e - ph} ({{\overset{z}{true}}_{i}})

where the electronic part is composed of an electronically diagonal on‐site part (

{\overset{H}{true}}^{on - site}

) and an electronically off‐diagonal coupling part (

{\overset{H}{true}}^{coup}

{\overset{H}{true}}_{ν μ, ν' μ'}^{el} = δ_{ν ν'} δ_{μ μ'} {\overset{H}{true}}_{ν μ, ν' μ'}^{on - site}

…”

Section: Vibronic Lattice Models and High‐dimensional Quantum Dynamicsmentioning

confidence: 99%

See 1 more Smart Citation

Quantum dynamical studies of ultrafast charge separation in nanostructured organic polymer materials: Effects of vibronic interactions and molecular packing

Polkehn

Eisenbrandt

Tamura

et al. 2017

Int J of Quantum Chemistry

View full text Add to dashboard Cite

show abstract

“…10 However, also the potential of this latter methodology has already been exploited by a number of researchers studying organic electronics and photobiology. [16][17][18][19][20] A unified formalism is present through the use of one-particle density matrices (1DM) and transition density matrices, a common ground, which allows for a clear comparison between the different methods and suggests extensions leading to a wide variety of routines for population analysis, as well as, orbital and density plotting, which are provided in this implementation. To our knowledge, a similarly comprehensive analysis toolbox has not been made available so far, let alone in a correlated ab initio framework.…”

Section: Introductionmentioning

confidence: 99%

New tools for the systematic analysis and visualization of electronic excitations. I. Formalism

Plasser¹,

Wormit²,

Dreuw³

2014

The Journal of Chemical Physics

473

772

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A variety of density matrix based methods for the analysis and visualization of electronic excitations are discussed and their implementation within the framework of the algebraic diagrammatic construction of the polarization propagator is reported. Their mathematical expressions are given and an extensive phenomenological discussion is provided to aid the interpretation of the results. Starting from several standard procedures, e.g., population analysis, natural orbital decomposition, and density plotting, we proceed to more advanced concepts of natural transition orbitals and attachment/detachment densities. In addition, special focus is laid on information coded in the transition density matrix and its phenomenological analysis in terms of an electron-hole picture. Taking advantage of both the orbital and real space representations of the density matrices, the physical information in these analysis methods is outlined, and similarities and differences between the approaches are highlighted. Moreover, new analysis tools for excited states are introduced including state averaged natural transition orbitals, which give a compact description of a number of states simultaneously, and natural difference orbitals (defined as the eigenvectors of the difference density matrix), which reveal details about orbital relaxation effects.

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“…Förster energy transfer rates have been measured in fluorene-based blends, of PF8 and F8BT polymers 14,15 , with transfer times of over 10 ps, which is much longer than the decoherence time. Experiments also indicate ultrafast exciton localisation in 100 fs in disordered polymers 12,16 which can be explained by intra-band and structural relaxation 12,[16][17][18] . It is not known which, if any, of these effects are generic for conjugated polymers and which are specific to particular chemical structures.…”

Section: Introductionmentioning

confidence: 99%

Subpicosecond Exciton Dynamics in Polyfluorene Films from Experiment and Microscopic Theory

et al. 2015

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Electronic energy transfer (EET) in organic materials is a key mechanism that controls the efficiency of many processes, including light harvesting antenna in natural and artificial photosynthesis, organic solar cells, and biological systems. In this paper we have examined EET in solid-state thin-films of polyfluorene, a prototypical conjugated polymer with ultrafast photoluminescence experiments and theoretical modelling. We observe EET occurring on a 680 ± 300 fs timescale by looking at the depolarisation of photoluminescence. An * To whom correspondence should be addressed independent, predictive microscopic theoretical model is built by defining 125 000 chromophores containing both spatial and energetic disorder appropriate for a spin-coated thin film. The model predicts time-dependent exciton dynamics, without any fitting parameters, using the incoherent Förster-type hopping model. Electronic coupling between the chromophores is calculated by an improved version of the usual line-dipole model for resonant energy transfer. Without the need for higher level interactions, we yet find that the model is in general agreement with the experimentally observed 680 ± 300 fs depolarisation caused by EET. This leads us to conclude that femtosecond EET in polyfluorene can be well described by conventional resonant energy transfer, as long as the relevant microscopic parameters are well captured. The implications of this finding are that dipole-dipole resonant energy transfer can in some circumstances be fully adequate to describe ultrafast EET without needing to invoke strong or intermediate coupling mechanisms.1

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Coherent exciton transport driven by torsional dynamics: a quantum dynamical study of phenylene-vinylene type conjugated systems

Cited by 34 publications

References 75 publications

Quantum dynamical studies of ultrafast charge separation in nanostructured organic polymer materials: Effects of vibronic interactions and molecular packing

Quantum dynamical studies of ultrafast charge separation in nanostructured organic polymer materials: Effects of vibronic interactions and molecular packing

New tools for the systematic analysis and visualization of electronic excitations. I. Formalism

Subpicosecond Exciton Dynamics in Polyfluorene Films from Experiment and Microscopic Theory

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