Quantitative Correlation between Carrier Mobility and Intermolecular Center-to-Center Distance in Organic Single Crystals

Park, Yoonkyung; Park, Kyung Sun; Jun, Byeongsun; Lee, Yong-Eun Koo; Lee, Sang Uck; Sung, Myung Mo

doi:10.1021/acs.chemmater.7b00827

Cited by 13 publications

(13 citation statements)

References 49 publications

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“…Notably, on the basis of our computed transfer integrals, hopping approaches such as Marcus theory are unable to reproduce the experimental trend, since the mobility is proportional to the square of the transfer integral value and the non‐monotonic trend in the transfer integral variation ( Figure ) would reflect in a non‐monotonic variation of mobility (e.g., 75% decrease with 1% elongation but 358% increase with 5% elongation, see Supporting Information), in clear contradiction with experimental reports. [ 31 ] This result confirms that comparing relative trends in charge mobility under the effect of different mechanical deformations is an ideal approach to highlight the main qualitative differences between theories.…”

Section: Resultssupporting

confidence: 71%

“…Our predicted relative variation of the mobility with strain is in very good agreement with experimental data in ref. [31]: our computations predict a monotonic increase in mobility up to 1979% (experimental 1854%) under 16% compression and a decrease up to 42% (experimental 97%) under 16% elongation. Notably, on the basis of our computed transfer integrals, hopping approaches such as Marcus theory are unable to reproduce the experimental trend, since the mobility is proportional to the square of the transfer integral value and the non‐monotonic trend in the transfer integral variation ( Figure ) would reflect in a non‐monotonic variation of mobility (e.g., 75% decrease with 1% elongation but 358% increase with 5% elongation, see Supporting Information), in clear contradiction with experimental reports.…”

Section: Resultsmentioning

confidence: 90%

“…So far, our analysis has been performed on a limited range of applied deformation, since rubrene single crystals show fractures for strains larger than

\pm 0.4 %

; [ 14 ] more in general, the vast majority of organic semiconductors have never been analyzed under strain larger than

3 %

. [ 30 ] A remarkable exception is TIPS, for which charge mobility has been measured under both compressive and tensile strain up to

16.7 %

, [ 31 ] the widest deformation range reported in the literature to date, showing outstanding monotonic increase in the charge carrier mobility under compression, while only a little decrease is observed under elongation. Our predicted relative variation of the mobility with strain is in very good agreement with experimental data in ref.…”

Section: Resultsmentioning

confidence: 99%

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Quantitative Prediction of the Electro‐Mechanical Response in Organic Crystals

2021

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Organic semiconductors’ inherent flexibility makes them appealing for advanced applications such as wearable electronics, e‐skins, or pressure sensors, and can even be used to enhance their intrinsic electronic properties. Unfortunately, these applications for organic materials are currently hindered by the lack of a quantitative understanding of the interplay between their electrical and mechanical properties. In this work, this gap is filled by presenting an accurate methodology able to predict quantitatively the effects of external deformation on the charge transport properties of any organic semiconductors. Three prototypical materials are investigated, showing that the experimental variation of charge carrier mobility with strain is fully reproduced, even in a wide range of deformations applied along different crystal axes. The results indicate that the intrinsic electro‐mechanical response of the materials varies by orders of magnitude within the class of organic semiconductors, a difference rationalized observing that the mobility trend is primarily influenced by the transfer integrals’ variation, rather than by a modification of the crystal phonons. In light of its robustness, accuracy, and low computational cost, this protocol represents an ideal tool to quantify the electro‐mechanical response in new organic compounds, thus establishing a reliable route for a full exploitation of strain engineering in advanced technologies.

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Section: Resultssupporting

confidence: 71%

Section: Resultsmentioning

confidence: 90%

“…So far, our analysis has been performed on a limited range of applied deformation, since rubrene single crystals show fractures for strains larger than

\pm 0.4 %

; [ 14 ] more in general, the vast majority of organic semiconductors have never been analyzed under strain larger than

3 %

. [ 30 ] A remarkable exception is TIPS, for which charge mobility has been measured under both compressive and tensile strain up to

16.7 %

Section: Resultsmentioning

confidence: 99%

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Quantitative Prediction of the Electro‐Mechanical Response in Organic Crystals

2021

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“…This contrasts with TES‐pentacene which packs in a 1D slipped stack motif and gives an inferior OTFT mobility, compared with TIPS‐pentacene, despite its higher magnitude transfer integral of 94 meV . For TIPS‐pentacene the relationship between X‐ray crystallographic packing, transfer integrals, and mobility has been widely investigated . These comparisons are similar to those made for NFAs in this study.…”

Section: Resultssupporting

confidence: 70%

Impact of Nonfullerene Acceptor Side Chain Variation on Transistor Mobility

Bristow

Thorley

White

et al. 2019

Adv Elect Materials

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Organic photovoltaic power conversion efficiencies exceeding 14% can largely be attributed to the development of nonfullerene acceptors (NFAs). Many of these molecules are structural derivatives of IDTBR and ITIC, two common NFAs. By modifying the chemical structure of the acceptor, the optical absorption, energy levels, and bulk heterojunction morphology can be tuned. However, the effect of structural modifications on NFA charge transport properties has not yet been fully explored. In this work, the relationship between chemical structure, molecular packing, and charge transport, as measured in organic thin-film transistors (OTFTs), is investigated for two high performance NFAs, namely O-IDTBR and ITIC, along with their structural derivatives EH-IDTBR and ITIC-Th. O-IDTBR exhibits a higher n-type saturation field effect mobility of 0.12 cm 2 V −1 s −1 compared with the other acceptors investigated. This can be attributed to the linear side chains of O-IDTBR which direct an interdigitated columnar packing motif. The study provides insight into the transport properties and molecular packing of NFAs, thereby contributing to understanding the relationship between chemical structure, material properties, and device performance for these materials. The high electron mobility achieved by O-IDTBR also suggests its applications can be extended to use as an n-type semiconductor in OTFTs.

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“…In the literature, it is reported that compressive strain along the π -π stacking distance reduces the molecular centerto-center distance, thus enhancing the charge transport in TIPS-pentacene and PTCDI-C8 [60]. However, our results for TIPS-pentacene indicates that the π -π stacking distance is nearly independent on the molecular center-to-center distance.…”

Section: Discussioncontrasting

confidence: 70%

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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Quantitative Correlation between Carrier Mobility and Intermolecular Center-to-Center Distance in Organic Single Crystals

Cited by 13 publications

References 49 publications

Quantitative Prediction of the Electro‐Mechanical Response in Organic Crystals

Quantitative Prediction of the Electro‐Mechanical Response in Organic Crystals

Impact of Nonfullerene Acceptor Side Chain Variation on Transistor Mobility

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

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