Tuning the Charge Transfer in F<i><sub>x</sub></i>‐TCNQ/Rubrene Single‐Crystal Interfaces

Krupskaya, Yulia; Lezama, Ignacio Gutiérrez; Morpurgo, Alberto F.

doi:10.1002/adfm.201502082

Cited by 19 publications

(36 citation statements)

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“…Mobility determined by Hall‐ and field‐effects agreed and were on the order of 1 cm 2 V −1 s −1 . In a subsequent work, the same group reported single crystal interfaces based on rubrene 3 and TCNQ, F2‐TCNQ 19 , and F4‐TCNQ to demonstrate increased interfacial charge transfer upon increasing the electron affinity of the acceptor material . Ambipolar charge transport with µ ( h + ) = 0.23 cm 2 V −1 s −1 and µ ( e − ) = 0.13 cm 2 V −1 s −1 has been observed for parallel TIPS‐PEN 4 and N,N′‐dioctyl perylene tetracarboxilic diimide single crystals .…”

Section: Charge Transportmentioning

confidence: 70%

Molecular Semiconductors for Logic Operations: Dead‐End or Bright Future?

et al. 2020

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The field of organic electronics has been prolific in the last couple of years, leading to the design and synthesis of several molecular semiconductors presenting a mobility in excess of 10 cm2 V−1 s−1. However, it is also started to recently falter, as a result of doubtful mobility extractions and reduced industrial interest. This critical review addresses the community of chemists and materials scientists to share with it a critical analysis of the best performing molecular semiconductors and of the inherent charge transport physics that takes place in them. The goal is to inspire chemists and materials scientists and to give them hope that the field of molecular semiconductors for logic operations is not engaged into a dead end. To the contrary, it offers plenty of research opportunities in materials chemistry.

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Section: Charge Transportmentioning

confidence: 70%

Molecular Semiconductors for Logic Operations: Dead‐End or Bright Future?

et al. 2020

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“…[2] To sum up, organic thermoelectrics composed of crystalline low-dimensional molecular metals present a promising alternative to existing material concepts, especially considering ongoing research to take full control over the amount of charge-transfer and band filling. [32] The peculiar phenomena observed in this material class such as violation of the WF law, the anomalous temperature dependence of the electrical conductivity or phonon drag effects in the thermopower, will furthermore open new possibilities in low-temperature thermoelectrics.…”

Section: Doi: 101002/adma201605682mentioning

confidence: 99%

“…While the absolute efficiency values still require further improvement, it is worth looking at the specific power output normalized to the active cross-sectional area of both crystals, as depicted on the right ordinate of Figure 4b. This key parameter for cost-per-watt in waste heat recovery [31] reaches values of 9 1 mW/cm 2 at Δ = 30 K being three orders of magnitude larger than those of thermoelectric devices based on polymers [2] .To sum up, organic thermoelectrics composed of crystalline low-dimensional molecular metals present a promising alternative to existing material concepts, especially considering ongoing research to take full control over the amount of charge-transfer and band filling [32] . The peculiar phenomena observed in this material class such as violation of the WF law, the anomalous temperaturedependence of the electrical conductivity or phonon drag effects in the thermopower, will furthermore unlock new possibilities in low-temperature thermoelectrics.…”

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confidence: 99%

Low‐Cost and Sustainable Organic Thermoelectrics Based on Low‐Dimensional Molecular Metals

et al. 2017

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A note on versions:The version presented here may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the repository url above for details on accessing the published version and note that access may require a subscription.For more information, please contact eprints@nottingham.ac.uk 1 DOI: 10.1002/((please add manuscript number)) Article type: Communication Low-Cost and Sustainable Organic Thermoelectrics Based on LowDimensional Molecular MetalsBy Florian Huewe*, Alexander Steeger*, Kalina Kostova, Laurence Burroughs, Irene Bauer, Peter Strohriegl, Vladimir Dimitrov, Simon Woodward and Jens Pflaum* F. Huewe [ †] , A. Steeger [ †] The dimensionless figure of merit measures a material's thermoelectric performancewhere electrical conductivity (resistivity ), Seebeck coefficient/thermopower , and thermal conductivity provide the power factor = 2 . Materials with high electrical conductivity and thermopower but low thermal conductivity are desirable to maximize and hence, the thermoelectric conversion efficiency. Approximately, is inversely proportional to which in turn is related to the electronic thermal conductivity el = via the Wiedemann-Franz (WF) law.Advances in have been achieved by tuning the doping of semiconductors to maximize the [6] together with reducing the phononic contribution to thermal conduction by means of nanostructured superlattice architectures [7,8] . To overcome the inherent limitations of ordinary materials, a dimensionality reduction of the electronic system has been proposed [9] . This can lead to a violation of the WF law [10,11] and to phonon drag contributions to the thermopower [12] . Complex crystal structures, e.g. Zintl compounds [13] and skutterudites [14] , have been evaluated as good thermoelectric 3 candidates due to reduced lattice thermal conductivity and electronic band structure tunability. These optimization strategies, together with the ability for low-cost production and low-temperature processibility, have recently raised interest in organic polymers [15] , such as PEDOT:Tos, reaching = 0.25 at room temperature (RT) [4] and thus advancing the value of = 1.2 obtained for Bi2Te3 (the best RT thermoelectric material to date [7] ). Herein, quasi-1D organic conductors based on small molecules constitute a new, sustainable approach towards organic thermoelectrics that provide many of the desired electrical and thermal properties described above. Additionally, they are lightweight and thermodynamically stable allowing for portable device manufacturing and long-term usage. In comparison to organic polymers the availability of electrically high-performing p-and ntype organic conductors facilitates the construction of all-organic thermoelectric devices.As a starting point we chose two of the best p-and n-type conducting radical ion salts, TTT2I3 (TTT = Tetrathiotetracene) and (DMe-DCNQI)2Cu (DMe-DCNQI = Dimethyl-Dicyanoquinonediimine).They form macroscopic needle-like sin...

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“…The phenomenon of charge transfer in molecular materials is of a particular interest both in fundamental and applied research in the field of organic electronics . Especially when considering interfaces formed by two different organic semiconductors, charge transfer from one semiconductor to the other can have dramatic effects and lead to interfacial electronic properties that differ drastically from the properties of the individual constituent materials . Indeed, the interfaces between two large‐gaps, initially insulating organic semiconductors can exhibit significantly enhanced electrical conductivity and in some cases even metallic behavior, as it has been observed in interfaces formed by single crystals of TTF (tetrathiofulvalene) and TCNQ (tetracyanoquinodimethane) .…”

mentioning

confidence: 99%

“…At the current stage, with no previous experiments reported, our work aims at identifying promising combinations of different molecular materials enabling the experimental realization of magnetic and conducting organic interfaces. This is essential because so far the number of conducting organic interfaces that have been investigated experimentally is limited, in no cases involving magnetic ions, and among all systems studied, only one was found to exhibit metallic interfacial electrical conductivity …”

mentioning

confidence: 99%

Charge Transfer, Band‐Like Transport, and Magnetic Ions at F₁₆CoPc/Rubrene Interfaces

Krupskaya

Rückerl

Knupfer

et al. 2016

Adv Materials Inter

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and among all systems studied, only one was found to exhibit metallic interfacial electrical conductivity. [ 5 ] We investigate heterostructures formed by a rubrene (tetraphenyltetracene) single crystal and an F 16 CoPc (fl uorinated Co-phthalocyanine) fi lm by means of charge transport and photoelectron spectroscopy. We fi nd that the F 16 CoPc/rubrene interface has signifi cantly enhanced electrical conductance. With the exception of TTF/TCNQ, [ 5 ] the room temperature resistivity of this interface is the lowest reported so far, and temperature dependent measurements show a decrease of the resistivity upon cooling (down to ≈130 K) indicating the occurrence of band-like transport. [20][21][22][23][24][25][26][27][28][29][30] By means of Hall effect measurements, we establish that charge transport is dominated by holes in the rubrene crystal and we fi nd that the value of the hole mobility virtually coincides with that measured in a class of recently investigated organic interfaces based on F x -TCNQ (fl uorinated tetracyanoquinodimethane) and rubrene single crystals. [ 13 ] As compared to all interfaces studied in this family, on the contrary, the hole density is higher in F 16 CoPc/rubrene, which explains the low value of the F 16 CoPc/rubrene resistivity. The results of the transport measurements are corroborated by Kelvin probe microscopy experiments that enable the alignment of the chemical potential across the F 16 CoPc/rubrene interface to be determined, and confi rm that a large transfer between the two materials should be expected. Finally, we perform photoelectron spectroscopy (PES) measurements on thin fi lm F 16 CoPc/rubrene heterostructures to show that the charge transfer at the interface involves electronic orbitals centered on the magnetic Cobalt ion of the F 16 CoPc molecules. We therefore conclude that the investigated system does allow the high electrical conductivity with the presence of magnetic ions to be combined at the interface.F 16 CoPc/rubrene interface devices were formed on a polydimethylsiloxane substrate. First, a rubrene single crystal (grown by physical vapor transport) was laminated on the substrate and then a 70-nm F 16 CoPc fi lm was evaporated (under high vacuum conditions) on top of the rubrene crystal. The transport properties of rubrene single crystals (identical to those used to assemble the interfaces) were investigated via fi eldeffect transistor (FET) measurements [ 31 ] as a characterization step, and showed a room temperature mobility between 12 and 20 cm 2 V −1 s −1 in devices in which the crystal was suspended on top of a gate electrode, in agreement with previous studies. [32][33][34] In order to maintain its quality, the rubrene crystal was kept at room temperature throughout the deposition of the evaporated fi lm. As a result, the morphology of the F 16 CoPc fi lm was expected to be far from ideal, as indeed indicated by atomic force microscopy measurements showing F 16 CoPc fi lms with rather rough surfaces, consisting of small grains with irregular orientation...

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Tuning the Charge Transfer in F_x‐TCNQ/Rubrene Single‐Crystal Interfaces

Cited by 19 publications

References 37 publications

Molecular Semiconductors for Logic Operations: Dead‐End or Bright Future?

Molecular Semiconductors for Logic Operations: Dead‐End or Bright Future?

Low‐Cost and Sustainable Organic Thermoelectrics Based on Low‐Dimensional Molecular Metals

Charge Transfer, Band‐Like Transport, and Magnetic Ions at F₁₆CoPc/Rubrene Interfaces

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Tuning the Charge Transfer in Fx‐TCNQ/Rubrene Single‐Crystal Interfaces

Cited by 19 publications

References 37 publications

Molecular Semiconductors for Logic Operations: Dead‐End or Bright Future?

Molecular Semiconductors for Logic Operations: Dead‐End or Bright Future?

Low‐Cost and Sustainable Organic Thermoelectrics Based on Low‐Dimensional Molecular Metals

Charge Transfer, Band‐Like Transport, and Magnetic Ions at F16CoPc/Rubrene Interfaces

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Product

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Tuning the Charge Transfer in F_x‐TCNQ/Rubrene Single‐Crystal Interfaces

Charge Transfer, Band‐Like Transport, and Magnetic Ions at F₁₆CoPc/Rubrene Interfaces