Trap Limited Exciton Transport in Conjugated Polymers

Athanasopoulos, Stavros; Hennebicq, Emmanuelle; Beljonne, David; Walker, Alison B.

doi:10.1021/jp802704z

Cited by 75 publications

(99 citation statements)

References 44 publications

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“…In each case, the KS orbitals are used to determine the exciton positions r I following Eq. (7) and (8) in the macroscopic system. The transition rates within each cube (or intra-cube transition rates) are calculated by Eq.…”

Section: Construction Of Macroscopic System and Monte Carlo Simulamentioning

confidence: 99%

“…To be more predictive, quantum chemical methods have been put forward in conjunction with a distributed monopole model to determine the exciton transition rates employing the Fermi golden rule. [5][6][7][8] However, all these methods assume a Gaussian distribution of exciton density of states as well as perturbation theories and harmonic approximations, whose validity is not generally established. More importantly, none of the methods above has considered explicitly the many-body wave-functions and energy levels of the excitons -both are important for exciton dynamics.…”

Section: Introductionmentioning

confidence: 99%

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First-principles simulations of exciton diffusion in organic semiconductors

Zhang

Lü

2011

Phys. Rev. B

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Exciton diffusion is crucial for the performance of organic semiconductors in photovoltaic and solid state lighting applications. We propose a first-principles approach that can predict exciton dynamics in organic semiconductors. The method is based on time-dependent density functional theory to describe energy and many-body wave-functions of excitons. Non-adiabatic ab initio molecular dynamics is used to calculate phonon-assisted transition rates between localized exciton states. Using Monte Carlo simulations, we determine exciton diffusion length, lifetime, diffusivity and harvesting efficiency in poly(3-hexylthiophene) (P3HT) polymers at different temperatures, which agree very well with experiments. We find that exciton diffusion is primarily determined by the density of states of low-energy excitons. A widely speculated diffusion mechanism, namely an initial downhill migration followed by thermally activated migration, is confirmed and elucidated by the simulations. Some general guidelines for designing more efficient organic solar cells are obtained from the simulations.

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Section: Construction Of Macroscopic System and Monte Carlo Simulamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

First-principles simulations of exciton diffusion in organic semiconductors

Zhang

Lü

2011

Phys. Rev. B

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“…[4] In amorphous or polycrystalline organic semiconductors, the diffusion length of singlet excitons is often 10nm or less as a result of exciton trapping. [5,6] However, reliability and comparability of ℓd measurements still remain an issue, even within one technique. [7][8][9] For example, for the thermally stable and chemically inert small molecule zinc phthalocyanine (ZnPc), reported ℓd-values range over one order of magnitude (see Table S1 in the Supplementary Information (SI)).…”

mentioning

confidence: 99%

Exciton Diffusion Length and Charge Extraction Yield in Organic Bilayer Solar Cells

et al. 2017

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A method for resolving the diffusion length of excitons and the extraction yield of charge carriers is presented based on the performance of organic bilayer solar cells and careful modeling. The technique uses a simultaneous variation of the absorber thickness and the excitation wavelength. Rigorously differing solar cell structures as well as independent photoluminescence quenching measurements give consistent results.

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“…Athanasopoulos et al applied a Monte Carlo approach to model the exciton diffusion dynamics in a conjugated polymer on a predetermined chain morphology. [17] However, the predicted diffusion lengths were an order of magnitude larger than experimental values, and they introduced trap sites at a concentration of 0.5 % to remedy the discrepancy between the theory and the experiment. A similar Monte Carlo algorithm has also been applied on host-guest crystalline system to both estimate the exciton diffusion length and to reveal the directionality of diffusion dynamics in the condensed phase.…”

Section: Introductionmentioning

confidence: 91%

“…The actual time the exciton is located at a site i is determined by calculating the hopping time to the jth neighbor by a random function [Eq. (12)]: [17,18] …”

Section: à3mentioning

confidence: 99%

Exciton Migration in Conjugated Dendrimers: A Joint Experimental and Theoretical Study

Köse¹,

Gräf²,

Kopidakis³

et al. 2009

ChemPhysChem

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We report a joint experimental and theoretical investigation of exciton diffusion in phenyl-cored thiophene dendrimers. Experimental exciton diffusion lengths of the dendrimers vary between 8 and 17 nm, increasing with the size of the dendrimer. A theoretical methodology is developed to estimate exciton diffusion lengths for conjugated small molecules in a simulated amorphous film. The theoretical approach exploits Fermi's Golden Rule to estimate the energy transfer rates for a large ensemble of bimolecular complexes in random relative orientations. Utilization of Poisson's equation in the evaluation of the Coulomb integral leads to very efficient calculation of excitonic couplings between the donor and the acceptor chromophores. Electronic coupling calculations with delocalized transition densities revealed efficient coupling pathways in the bulk of the material, but do not result in strong couplings between the chromophores which are calculated for more localized transition densities. The molecular structures of dendrimers seem to be playing a significant role in the magnitude of electronic coupling between chromophores. Simulated diffusion lengths correlate well with the experimental data. The chemical structure of the chromophore, the shape of the transition densities and the exciton lifetime are found to be the most important factors in determining the size of the exciton diffusion length in amorphous films of conjugated materials.

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Trap Limited Exciton Transport in Conjugated Polymers

Cited by 75 publications

References 44 publications

First-principles simulations of exciton diffusion in organic semiconductors

First-principles simulations of exciton diffusion in organic semiconductors

Exciton Diffusion Length and Charge Extraction Yield in Organic Bilayer Solar Cells

Exciton Migration in Conjugated Dendrimers: A Joint Experimental and Theoretical Study

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