Dynamical localization corrections to band transport

Fratini, Simone; Ciuchi, S.

doi:10.1103/physrevresearch.2.013001

Cited by 34 publications

(45 citation statements)

References 43 publications

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“…The suppressed transient localization length of form I relative to form II is attributed to both a small charge transfer integral and large sensitivity to dynamic disorder as illustrated in Fig. 9(c) and reported in several theoretical studies [4,57].…”

Section: Sensitivity Of Charge Transfer Integrals To the Dynamic Disosupporting

confidence: 59%

Enhancement of charge transfer in thermally-expanded and strain-stabilized TIPS-pentacene thin films

Wan²,

Smilgies

et al. 2020

Phys. Rev. Research

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We present an extensive study of the optical and electronic properties of TIPS-pentacene thin films utilizing in situ x-ray diffraction, polarized optical spectroscopy, and ab initio density functional theory. The influence of molecular packing on the properties are reported for thin films deposited in the temperature range from 25 • C to 140 • C and for films that are strain stabilized at their as-deposited lattice spacings after cooling to room temperature. Anisotropic thermal expansion causes relative displacement of neighboring molecules while maintaining a nearly constant stacking distance. This leads to a large blueshift in the absorption spectrum as the temperature increases. The blueshift largely reverses a redshift at room temperature compared to the solution absorption spectrum. A reduction in the ratio of the first two vibronic peaks relative to the solution spectrum is also observed. This combination of electronic and vibronic effects is a signature of charge transfer excitonic coupling with a positive coupling constant J CT , which depends sensitively on the alignment of the nodes of the frontier molecular orbitals with those on neighboring molecules. These effects are also correlated with the sign and magnitude of electron and hole charge transfer integrals t e and t h calculated from density functional theory that provide additional evidence for charge transfer mediated coupling, as well as insight into the origin of an experimentally observed enhancement of the field-effect transistor mobility in strain-stabilized thin films. The results suggest approaches to improve carrier mobility in strained thin films and for optical monitoring of electronic changes.

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Section: Sensitivity Of Charge Transfer Integrals To the Dynamic Disosupporting

confidence: 59%

Enhancement of charge transfer in thermally-expanded and strain-stabilized TIPS-pentacene thin films

Wan²,

Smilgies

et al. 2020

Phys. Rev. Research

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show abstract

“…The dependence on energetic disorder can be obtained from the above expression by substituting the definition σ / ffiffiffiffiffiffiffiffiffiffiffi ffi λJk B T p I (refs. 29,30,38 ), which yields e, Corresponding increase of the mobility under compressive strain for three devices, A (for which the four-terminal mobility is reported), B and C (for which two-terminal saturated mobilities are reported). f, Histograms of the room-temperature mobility for rubrene and 13 C-rubrene single crystals, showing a small but statistically significant suppression of mobility in the heavier isotope that is consistent with predictions of the TL framework.…”

Section: Box 1 | Some Key Examples Of Structure-property Relationshipmentioning

confidence: 96%

“…Such semiclassical 'band' picture holds provided that the mean free path between collisions is much larger than the lattice spacing or, equivalently, when the semiclassical scattering rate 1/τ is much smaller than the electronic transfer rate J/ħ between lattice sites 28,29 . Assuming the Drude formula μ = eτ/m*, where the effective band mass m* ≈ ħ 2 / (2Ja 2 ), with a ≈ 6 Å a typical intermolecular distance, and setting the phenomenological condition (ħ/τ)/J = 0.25 yields approximately μ ≳ 50 cm 2 V -1 s -1 as a lower bound for the applicability of Bloch-Boltzmann (band) transport 30 .…”

Section: In Inorganic Semiconductors Including the Observation Of Anmentioning

confidence: 99%

“…The mobility decreases with dynamical disorder as a power law, μ∝(σ/J) −ν , with J setting the scale of the electronic bandwidth and ν a material-dependent exponent that has been calculated to be in the range 1.5 < ν < 3.5 (ref. 30 ). While the presence of thermal molecular disorder is tied to the very nature of weakly bonded molecular solids, the large variability of ratios σ/J observed across different compounds (Table 1) shows that there is ample room for optimizing this parameter, and hence the mobility, via a proper engineering of intermolecular interactions.…”

mentioning

confidence: 99%

“…According to the scaling form given above, reducing the disorder ratio σ/J from 0.5 to 0.3 can result in an improvement of μ by up to a factor of six. Of similar importance are also the dynamic fluctuations of the diagonal electron-phonon coupling and the site energies 30,39,41 .…”

mentioning

confidence: 99%

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Conjugated polymers and molecular semiconductors are emerging as a viable semiconductor technology in industries such as displays, electronics, renewable energy, sensing and healthcare. A key enabling factor has been significant scientific progress in improving their charge transport properties and carrier mobilities, which has been made possible by a better understanding of the molecular structure-property relationships and the underpinning charge transport physics. Here we aim to present a coherent review of how we understand charge transport in these high-mobility van der Waals bonded semiconductors. Specific questions of interest include estimates for intrinsic limits to the carrier mobilities that might ultimately be achievable; a discussion of the coupling between charge and structural dynamics; the importance of molecular conformations and mesoscale structural features; how the transport physics of conjugated polymers and small molecule semiconductors are related; and how the incorporation of counterions in doped films-as used, for example, in bioelectronics and thermoelectric devices-affects the electronic structure and charge transport properties.

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On the Largest Possible Mobility of Molecular Semiconductors and How to Achieve It

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Padula

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et al. 2020

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We use a large database of known molecular semiconductors to define a plausible physical limit to the charge carrier mobility achievable within this materials class, and a clear path toward this limit. From a detailed study of the desirable properties in a large dataset, it is possible to establish whether such properties can be optimized independently and what would be a reasonably achievable optimum for each of them, regardless of the transport mechanism considered. We compute all relevant parameters from a set of almost five thousand known molecular semiconductors, finding that the best known materials are not ideal with respect to all properties. These parameters in decreasing order of importance are realized to be the molecular area, the non-local electron-phonon coupling, the two-dimensional nature of transport, the local electron-phonon coupling and the highest transfer integral. We also find that the key properties related to the charge transport are either uncorrelated or 'constructively' correlated (i.e. they improve together) concluding that a ten-fold increase in mobility is within reach in a statistical sense, on the basis of the available data. We demonstrate that high throughput screenings, when coupled with physical models of transport produce not only specific target materials, as it is done also here, but a more general physical understanding of the materials space and the opportunities of further development.

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Dynamical localization corrections to band transport

Cited by 34 publications

References 43 publications

Enhancement of charge transfer in thermally-expanded and strain-stabilized TIPS-pentacene thin films

Enhancement of charge transfer in thermally-expanded and strain-stabilized TIPS-pentacene thin films

Charge transport in high-mobility conjugated polymers and molecular semiconductors

On the Largest Possible Mobility of Molecular Semiconductors and How to Achieve It

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