Vibronic Coupling in the Ground and Excited States of Oligoacene Cations

Sánchez‐Carrera, Roel S.; Coropceanu, Veaceslav; Filho, Demétrio A. da Silva; Friedlein, Rainer; Osikowicz, Wojciech; Murdey, Richard; Suess, C.; Salaneck, W. R.; Brédas, Jean‐Luc

doi:10.1021/jp057462p

Cited by 141 publications

(132 citation statements)

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“…This trend suggests that the strength of the overall vibronic interactions also initially increases with the size of the system and then decreases in longer systems. This behaviour is in marked contrast with that found for oligoacenes and their derivatives (Coropceanu et al 2002aMalagoli et al 2004;Sánchez-Carrera et al 2006) where the total relaxation energy is inversely proportional to the size of the system. In addition, as seen from table 1, the profile of the first ionization in small systems is highly asymmetric; this asymmetry, however, gradually decreases with system size, so that in T 8 the band can be modelled with a perfectly symmetric Gaussian shape.…”

Section: (A ) Ultraviolet Photoelectron Spectroscopy Datacontrasting

confidence: 88%

“…We have recently shown (Sánchez-Carrera et al 2006) that in oligoacenes BHandHLYP overestimates the relaxation energies related to ionization processes in oligoacenes, while the non-hybrid BLYP functional underestimates the relaxation (by up to 30%); overall, the best agreement between simulated and experimental UPS spectra in oligoacenes was obtained at the B3LYP level. In the case of oligothiophenes, neither BHandHLYP nor B3LYP is actually able to reproduce very well the shape of the first ionization band.…”

Section: ð4:2þmentioning

confidence: 93%

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Hole-vibronic coupling in oligothiophenes: impact of backbone torsional flexibility on relaxation energies

Filho

Coropceanu

Fichou

et al. 2007

Phil. Trans. R. Soc. A.

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Density functional theory calculations together with highly resolved gas-phase ultraviolet photoelectron spectroscopy have been applied to oligothiophene chains with up to eight thiophene rings. One of the important parameters governing the charge transport properties in the condensed phase is the amount of energy relaxation upon ionization. Here, we investigate the impact on this parameter of the backbone flexibility present in oligothiophenes as a result of inter-ring torsional motions. With respect to oligoacenes that are characterized by a coplanar and rigid backbone, the torsional flexibility in oligothiophenes adds to the relaxation energy and leads to the broadening of the first ionization peak, making its analysis more complex.

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Section: (A ) Ultraviolet Photoelectron Spectroscopy Datacontrasting

confidence: 88%

Section: ð4:2þmentioning

confidence: 93%

Hole-vibronic coupling in oligothiophenes: impact of backbone torsional flexibility on relaxation energies

Filho

Coropceanu

Fichou

et al. 2007

Phil. Trans. R. Soc. A.

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“…The results from calculations of energy magnitudes related to charge transport are known to be highly dependent on the underlying theoretical details, 49,50 which largely reflects the composition of the expression chosen to represent exchange-correlation effects at a nanoscopic level. One of these magnitudes is the so-called reorganization energy ( ), which can be viewed as the energy needed to switch from the initial | M ·+(−) N to the final | M N ·+(−) molecular state, as a consequence of charge migration across the sample.…”

Section: Single-molecule Magnitudesmentioning

confidence: 99%

Theoretical study of stability and charge-transport properties of coronene molecule and some of its halogenated derivatives: A path to ambipolar organic-based materials?

Sancho‐García

Pérez-Jiménez

2014

The Journal of Chemical Physics

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We have carefully investigated the structural and electronic properties of coronene and some of its fluorinated and chlorinated derivatives, including full periphery substitution, as well as the preferred orientation of the non-covalent dimer structures subsequently formed. We have paid particular attention to a set of methodological details, to first obtain single-molecule magnitudes as accurately as possible, including next the use of modern dispersion-corrected methods to tackle the corresponding non-covalently bound dimers. Generally speaking, this class of compounds is expected to self-assembly in neighboring π -stacks with dimer stabilization energies ranging from -20 to -30 kcal mol −1 at close distances around 3.0-3.3 Å. Then, in a further step, we have also calculated hole and electron transfer rates of some suitable candidates for ambipolar materials, and corresponding charge mobility values, which are known to critically depend on the supramolecular organization of the samples. For coronene and per-fluorinated coronene, we have found high values for their hopping rates, although slightly smaller for the latter due to an increase (decrease) of the reorganization energies (electronic couplings).

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“…To visualize characteristic differences in the measured data, each spectrum was fitted to a sum of three Gaussian curves corresponding to elastic tunneling and two vibronic side peaks at higher energy [16]. Because of energy broadening and a multitude of possible vibrational modes with different symmetries [23][24][25], there is some arbitrariness in choosing the peak positions for fitting [26]. The data are reproduced well by the fits as demonstrated in Fig.…”

mentioning

confidence: 99%

Symmetry Dependence of Vibration-Assisted Tunneling

et al. 2013

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We present spatially resolved vibronic spectroscopy of individual pentacene molecules in a doublebarrier tunneling junction. It is observed that even for this effective single-level system the energy dissipation associated with electron attachment varies spatially by more than a factor of 2. This is in contrast to the usual treatment of electron-vibron coupling in the Franck-Condon picture. Our experiments unambiguously prove that the local symmetry of initial and final wave function determines the dissipation in electron transport. DOI: 10.1103/PhysRevLett.110.136101 PACS numbers: 68.37.Ef, 63.22.Àm, 73.40.Gk, 73.63.Àb In organic and molecular electronics the electrons are much more spatially confined as compared to inorganic semiconductors, leading to a much stronger electronvibron (e-) coupling [1][2][3]. Therefore, e-coupling gives rise to substantial dissipation in such systems, which should be minimized in electronic devices. When an electron tunnels into a given molecule (electron attachment), the nuclei will relax, giving rise to the so-called reorganization energy, a process that is usually treated in the Franck-Condon picture [1]. In the latter, the e-coupling strength for all modes is inferred from projecting the atomic displacements that arise upon electron attachment onto the vibrational eigenmodes [1,4,5]. Whereas the wave functions of the vibrational states are crucial in the Franck-Condon picture, it does not account for the electronic wave functions. In contrast to that, we show in this Letter that the spatial position of the electron injection as well as the local wave function symmetry dramatically affect the e-coupling.Our scanning tunneling microscopy (STM-)based experiments are performed in a double-barrier tunneling junction, enabling spatially resolved vibronic spectroscopy [6,7]. This regime is highly relevant, resembling electron hopping in organic and molecular electronics. Note that vibronic spectroscopy is very different from usual STMbased inelastic electron tunneling spectroscopy [8], for which it has been realized that the symmetries of wave functions play an important role [9][10][11].As a model system we chose pentacene, which is widely used in organic electronics and one of the best studied systems [4,5,12,13]. We consider only transport involving the first molecular resonances, attributed to occupation and depletion of the lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) level, respectively. Effectively, this renders a single-level system. If several molecular orbitals are closely spaced in energy, tunneling into different orbitals and mixing of vibronic states [6,14] may lead to spatial variations of the e-coupling, which can be ruled out here. In our system, transport involving further orbitals (LUMO þ 1, HOMO À 1) can be excluded due to energy differences of more than 1 eV [12,15].In our low-temperature STM setup we use ultrathin insulating films on copper single crystals as substrates giving rise to a double-barrier tunneling jun...

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Vibronic Coupling in the Ground and Excited States of Oligoacene Cations

Cited by 141 publications

References 43 publications

Hole-vibronic coupling in oligothiophenes: impact of backbone torsional flexibility on relaxation energies

Hole-vibronic coupling in oligothiophenes: impact of backbone torsional flexibility on relaxation energies

Theoretical study of stability and charge-transport properties of coronene molecule and some of its halogenated derivatives: A path to ambipolar organic-based materials?

Symmetry Dependence of Vibration-Assisted Tunneling

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