Electronic spectra and transitions of the fullerene C60

Leach, Sydney; Vervloët, M.; Després, A.; Bréhéret, E.; Hare, Jonathon; Dennis, T. John S.; Kroto, Harold W.; Taylor, Roger; Walton, D. R. M.

doi:10.1016/0301-0104(92)80012-k

Cited by 499 publications

(361 citation statements)

References 29 publications

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“…49 The small sharp 1.75 eV absorption is due to the formation of a "Frenkel exciton" (electron hole pair within the same fullerene). 29,49 The direct excitation of this state is forbidden by the selection rules of the icosahedral fullerene, 55,56 but emission from this state can be observed in photoluminescence spectra of PCBM. 49 The SPV spectrum of the PCBM film contains a negative feature at 1.1−1.4 eV and a positive one at 1.4−2.3 eV.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

P3HT:PCBM Bulk-Heterojunctions: Observing Interfacial and Charge Transfer States with Surface Photovoltage Spectroscopy

et al. 2014

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Surface photovoltage (SPV) spectra are reported for separate films of (6,6)-phenyl-C61-butyric acid methyl ester (PCBM) and for regioregular and regiorandom poly(3-hexylthiophene) (P3HT):PCBM bulk heterojunctions, as a function of wavelength, film thickness, thermal annealing, and substrate. In PCBM films, two photovoltage features are observed at 1.1–1.4 eV (F1) and 1.4–2.3 eV (F2), which are assigned to excitation of charge transfer states at the interface (F1) and in the bulk (F2) of the film. In BHJ films, five different photovoltage features are observed at 0.75–0.9 eV (F1), 0.9–1.3 eV (F2), 1.3–1.8 eV (F3), 1.8–2.0 eV (F4), and 2.0–2.4 eV (F5). This data can be analyzed on the basis of optical absorbance and fluorescence spectra of the films, and using SPV spectra for PCBM and P3HT only films, and for a BHJ film containing P3HT nanofibers for comparison. SPV features are assigned to states at the polymer–substrate interface (F1 and F2), the P3HT:PCBM charge transfer state (F3), the self-ionized (CT) state of P3HT (F4), and the band gap transition of P3HT (F5). This interpretation is also consistent with molecular orbital energy diagrams and electron microscopy-derived topological maps of the films. Photovoltage sign and substrate dependence can be understood with the depleted semiconductor model. Features F1–4 are caused by polarization of electrostatically bound charge pairs by the built-in electric field at the substrate–BHJ interface, whereas F5 is due to transport of free charge carriers through the film and through the substrate film interface. This work will promote the understanding of photochemical charge generation and transport in organic photovoltaic films.

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Section: ■ Results and Discussionmentioning

confidence: 99%

P3HT:PCBM Bulk-Heterojunctions: Observing Interfacial and Charge Transfer States with Surface Photovoltage Spectroscopy

et al. 2014

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“…Exactly the same conclusions are attained for LES2; which are in good agreement with the experimental spectrum of C60, wherein the 2.0 to 3.0 eV energy range corresponds only to forbidden transitions. [75,76] In view of that, other LESs are expected to be inaccessible by photon absorption within the mentioned energy range. The excitation corresponding to a HOMO-to-LUMO transition lies at 3.48 eV and leads to the CTS lowest in energy.…”

Section: Extent Of Charge Separation and Exciton Delocalization For Ementioning

confidence: 99%

Theoretical estimation of the rate of photoinduced charge transfer reactions in triphenylamine C₆₀ donor–acceptor conjugate

2016

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Fullerene based molecular heterojunctions such as the [6,6]-pyrrolidine-C60 donor-acceptor conjugate containing triphenylamine (TPA) are potential materials for high-efficient dye-sensitized solar cells. In this work, we estimate the rate constants for the photoinduced charge separation and charge recombination processes in TPA-C60 using the unrestricted and time-dependent DFT methods. Different schemes are applied to evaluate excited state properties and electron transfer parameters (reorganization energies, electronic couplings, and Gibbs energies). The use of open-shell singlet or triplet states, several density functionals and continuum solvation models is discussed. Strengths and limitations of the computational approaches are highlighted. The present benchmark study provides an overview of the expected performance of DFT-based methodologies in the description of photoinduced charge transfer reactions in fullerene heterojunctions.2

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“…Let us begin with fullerene, a molecule whose spectrum has already been the subject of extensive experimental 51,52 and theoretical 22,41,51,[53][54][55] studies. Our calculations have been performed with the molecule lying in a cubic supercell with side length of 35a 0 , using the PBE XC functional.…”

Section: Application To Large Molecules: Fullerene and Chlorophyll Amentioning

confidence: 99%

Turbo charging time-dependent density-functional theory with Lanczos chains

Rocca

Gebauer

Saad

et al. 2008

The Journal of Chemical Physics

246

309

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We introduce a new implementation of time-dependent density-functional theory which allows the entire spectrum of a molecule or extended system to be computed with a numerical effort comparable to that of a single standard ground-state calculation. This method is particularly well suited for large systems and/or large basis sets, such as plane waves or real-space grids. By using a super-operator formulation of linearized timedependent density-functional theory, we first represent the dynamical polarizability of an interacting-electron system as an off-diagonal matrix element of the resolvent of the Liouvillian super-operator. One-electron operators and density matrices are treated using a representation borrowed from time-independent density-functional perturbation theory, which permits to avoid the calculation of unoccupied Kohn-Sham orbitals. The resolvent of the Liouvillian is evaluated through a newly developed algorithm based on the non-symmetric Lanczos method. Each step of the Lanczos recursion essentially requires twice as many operations as a single step of the iterative diagonalization of the unperturbed Kohn-Sham Hamiltonian. Suitable extrapolation of the Lanczos coefficients allows for a dramatic reduction of the number of Lanczos steps necessary to obtain well converged spectra, bringing such number down to hundreds (or a few thousands, at worst) in typical plane-wave pseudopotential applications. The resulting numerical workload is only a few times larger than that needed by a ground-state Kohn-Sham calculation for a same system. Our method is demonstrated with the calculation of the spectra of benzene, C60 fullerene, and of chlorofyll a.

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Electronic spectra and transitions of the fullerene C60

Cited by 499 publications

References 29 publications

P3HT:PCBM Bulk-Heterojunctions: Observing Interfacial and Charge Transfer States with Surface Photovoltage Spectroscopy

P3HT:PCBM Bulk-Heterojunctions: Observing Interfacial and Charge Transfer States with Surface Photovoltage Spectroscopy

Theoretical estimation of the rate of photoinduced charge transfer reactions in triphenylamine C₆₀ donor–acceptor conjugate

Turbo charging time-dependent density-functional theory with Lanczos chains

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Electronic spectra and transitions of the fullerene C60

Cited by 499 publications

References 29 publications

P3HT:PCBM Bulk-Heterojunctions: Observing Interfacial and Charge Transfer States with Surface Photovoltage Spectroscopy

P3HT:PCBM Bulk-Heterojunctions: Observing Interfacial and Charge Transfer States with Surface Photovoltage Spectroscopy

Theoretical estimation of the rate of photoinduced charge transfer reactions in triphenylamine C60 donor–acceptor conjugate

Turbo charging time-dependent density-functional theory with Lanczos chains

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Theoretical estimation of the rate of photoinduced charge transfer reactions in triphenylamine C₆₀ donor–acceptor conjugate