Organic Molecular Crystals

Silinsh, E. A.

doi:10.1007/978-3-642-81464-8

Cited by 546 publications

(294 citation statements)

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“…The experimental band gap is 2.2 eV. 19 However, an underestimation of the band gap is not unusual for GGA/DFT and, in general, doesn't much affect the other features of the electronic structure. The DOS peak of the HOMO (just below 0 eV) and of the LUMO (at 1 eV) are both well separated from the other peaks.…”

Section: Resultsmentioning

confidence: 99%

Anisotropy of the mobility of pentacene from frustration

et al. 2003

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Section: Resultsmentioning

confidence: 99%

Anisotropy of the mobility of pentacene from frustration

et al. 2003

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“…23,24 In these systems, electron exchange is negligible and each chromophore has its own electrons. Frenkel excitons are tightly bound electron-hole pairs that hop coherently or incoherently across the aggregate.…”

Section: Spectra and Energy Funneling In Dendrimersmentioning

confidence: 99%

“…coherent or incoherent via the Forster-Dexter mechanism. 23, 24 We estimate the electrostatic interaction between electronic modes on neighboring segments chemically bonded through the meta-positions to be ∼500 cm -1 . This value is supported by direct calculations of absorption spectra in the compact (family A) dendrimers, which show a weak Davydov-like splitting ∼200-600 cm -1 in the band-edge transition.…”

Section: Spectra and Energy Funneling In Dendrimersmentioning

confidence: 99%

“…This is a typical value for J aggregates, 25 biological antenna complexes, 26 and molecular crystals. 23, 24 The CEO approach can be readily applied for very large molecules with thousands of atoms. The lack of long-range electronic coherence allows us to truncate the density matrix and only retain off-diagonal elements of closely lying atoms.…”

Section: Spectra and Energy Funneling In Dendrimersmentioning

confidence: 99%

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Localized Electronic Excitations in Phenylacetylene Dendrimers

1998

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Electron-hole pairs created upon optical excitation of conjugated dendrimers (fractal antenna macromolecules) are shown to be localized within segments connected by benzene rings substituted at the meta-position. The absorption spectra of two families of dendrimers are analyzed using collective electronic normal modes representing the changes in charge and bond-order distributions induced by the optical field. The present approach may be used in the design of artificial light-harvesting antennae with controlled energy-funneling pathways.

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“…While in inorganic semiconductors with ε r > 10 the binding energy of excitons is on the order of 10 meV, in organic semiconductors, in which ε r is typically between 2 and 4, 3 the binding energy of excitons is on the order of 1 eV. 4 The puzzling question arises then regarding the mechanism that could provide an efficient dissociation of EHPs with such a huge binding energy as compared to the thermal energy at room temperature, kT ≃ 0.025 eV.Numerous experimental and theoretical studies have been dedicated to the dissociation problem of EHPs in organic semiconductors. There is no chance to review all of them in the current report.…”

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confidence: 99%

Calculating the Efficiency of Exciton Dissociation at the Interface between a Conjugated Polymer and an Electron Acceptor

Baranovskiǐ

Wiemer

Nenashev

et al. 2012

J. Phys. Chem. Lett.

101

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The decisive feature of any material designed for photovoltaic applications is the dissociation efficiency of photogenerated excitons. This efficiency is essentially governed by the Coulomb attraction between electrons and holes. Because the dielectric constant in organic materials is rather low (ε r ≈ 3), the exciton binding energy is much larger than the thermal energy at room temperature, so that thermally governed dissociation seems improbable. Experiments show that while the dissociation probability for electron−hole pairs is indeed very low in the bulk samples, it becomes close to unity at intrinsic interfaces between two organic materials, an electron donor (usually a conjugated polymer) and an electron acceptor (usually a fullerene derivative). The driving force for this dissociation is still a matter of controversy. This Perspective provides a theoretical analysis of possible mechanisms for the efficient dissociation of electron−hole pairs at internal organic interfaces despite the strong Coulomb attraction between the charges. I t is one of the main challenges in the research on organic materials to reveal the mechanism responsible for the efficient dissociation of electron−hole pairs (EHPs) created by light. The interest of researchers in the dissociation problem is caused mainly by perspectives of photovoltaic applications of organic semiconductors. Such materials usually exhibit very high light absorption coefficients, which, combined with lowcost processing, makes them promising for applications in solar cells. 1,2 However, it is not the efficient light absorption itself but rather the combination of the efficient absorption with the efficient photocurrent generation that makes a material favorable for photovoltaic applications. The decisive step in photocurrent generation is the dissociation of EHPs created by light. In the dissociation process, the electron and hole must overcome their mutual Coulomb attraction, determined by the energywhere e is the elementary charge, ε r is the relative dielectric constant of the surrounding media, ε 0 is the permittivity of vacuum, and r is the electron−hole separation. While in inorganic semiconductors with ε r > 10 the binding energy of excitons is on the order of 10 meV, in organic semiconductors, in which ε r is typically between 2 and 4, 3 the binding energy of excitons is on the order of 1 eV. 4 The puzzling question arises then regarding the mechanism that could provide an efficient dissociation of EHPs with such a huge binding energy as compared to the thermal energy at room temperature, kT ≃ 0.025 eV.Numerous experimental and theoretical studies have been dedicated to the dissociation problem of EHPs in organic semiconductors. There is no chance to review all of them in the current report. Interested readers can find a comprehensive description of the research field in recent review articles. 1,3 Here, we only briefly describe the state of the research field.The first organic solar cells tested in the 1970s used a single material, sandwiched...

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Organic Molecular Crystals

Cited by 546 publications

References 0 publications

Anisotropy of the mobility of pentacene from frustration

Anisotropy of the mobility of pentacene from frustration

Localized Electronic Excitations in Phenylacetylene Dendrimers

Calculating the Efficiency of Exciton Dissociation at the Interface between a Conjugated Polymer and an Electron Acceptor

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