Determination of electron affinity of electron accepting molecules

Kanai, Kaname; Akaike, Kouki; Koyasu, Kiichirou; Sakai, Kentaro; Nishi, Toshio; Kamizuru, Yasunori; Nishi, T.; Ouchi, Yukio; Seki, Kazuhiko

doi:10.1007/s00339-008-5021-1

Cited by 115 publications

(145 citation statements)

References 16 publications

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“…Specific properties influence the physics and the stability of the system: the large electron affinity of TCNQ (A = 4.23 eV) 24 makes it acquire charge both from the surface and from Cs, which fully donates its valence electron and establishes ionic, nondirectional CsÀN bonds, with an associated high rotational freedom of the molecules around the metal. This large flexibility makes the complexes particularly adaptable to different steric constraints and allows maximizing the number of NÀAg bonds (three per molecule, Figure 1c) that drive the surfaceÀadlayer interaction energetics, while preserving the hydrogen bonds mediating the intercomplex attractive interaction.…”

Section: Resultsmentioning

confidence: 99%

“…24 First we consider 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ), where all H atoms are substituted with F atoms. This molecule has A = 5.08 eV 24 (0.85 eV higher than TCNQ), and its ability to increase the work-function of several substrates has been Total energy of periodically repeated networks in the gas phase at different intercomplex distances. The energy zero is set at the (6,3,À3,6) configuration (denoted here 633) for all alkaliÀTCNQ 4 .…”

Section: Articlementioning

confidence: 99%

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Fine-Tuning the Electrostatic Properties of an Alkali-Linked Organic Adlayer on a Metal Substrate

2013

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The performance of modern organic electronic devices is often determined by the electronic level alignment at a metal–organic interface. This property can be controlled by introducing an interfacial electrostatic dipole via the insertion of a stable interlayer between the metallic and the organic phases. Here, we use density functional theory to investigate the electrostatic properties of an assembled structure formed by alkali metals coadsorbed with 7,7,8,8-tetracyanoquinodimethane (TCNQ) molecules on a Ag(100) substrate. We find that the interfacial dipole buildup is regulated by the interplay of adsorption energetics, steric constraints and charge transfer effects, so that choosing chemical substitutions within TCNQ and different alkali metals provides a rich playground to control the systems’ electrostatics and in particular fine-tune its work-function shift

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Section: Resultsmentioning

confidence: 99%

Section: Articlementioning

confidence: 99%

Fine-Tuning the Electrostatic Properties of an Alkali-Linked Organic Adlayer on a Metal Substrate

2013

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“…The reported LUMO values vary between -3.7 eV and -4.3 eV. 15,[30][31][32] Even if the determination of energy levels is done with one consistent method in pristine materials, the results may not be transferable to blend films and devices, because effects such as aggregation, crystallization and interface dipoles can shift energy levels by up to 0.5 eV. [33][34][35][36][37] These uncertainties in energy levels are relevant for material design rules and for the estimation of efficiency potentials as done by Scharber et al 15 The present paper uses electroluminescence (EL) and photoluminescence (PL) measurements of polymer:fullerene devices and films to study the relationship between interfacial energetics and charge generation and recombination.…”

Section: Introductionmentioning

confidence: 99%

Competition between the Charge Transfer State and the Singlet States of Donor or Acceptor Limiting the Efficiency in Polymer:Fullerene Solar Cells

Faist¹,

Kirchartz²,

et al. 2011

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We study the appearance and energy of the charge transfer (CT) state using measurements of Electroluminescence (EL) and Photoluminescence (PL) in blend films of high-performance polymers with fullerene acceptors. EL spectroscopy provides a direct probe of the energy of the interfacial states without the need to rely on the LUMO and HOMO energies as estimated in pristine materials. For each polymer, we use different fullerenes with varying LUMO levels as electron acceptors, in order to vary the energy of the CT state relative to the blend with [6,6]-phenyl C61-butyric acid methyl ester (PCBM). As the energy of the CT state emission approaches the absorption onset of the blend component with the smaller optical bandgap, , we observe a transition in the EL spectrum from CT emission to singlet emission from the component with the smaller bandgap. The appearance of component singlet emission coincides with reduced photocurrent and fill factor. We conclude that the open circuit voltage is limited by the smaller bandgap of the two blend components. From the losses of the studied materials, we derive an empirical limit for the open circuit voltage: 2

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“…Kanai et al [12] showed that the EA of tetracyanoquinodimethane can be increased from ≈4.20 eV for TCNQ to ≈5.10 eV for F4-TCNQ, following a nearly linear correlation with the number of fluorine substituents. In the present study, we investigate 2,2′-(perfluoronaphthalene-2,6-diylidene) dimalononitrile (F6-TCNNQ) (Figure 1b), a molecule first synthesized by Koech et al as F6-TNAP, which was predicted to have a larger EA than F4-TCNQ by density functional theory (DFT) calculations and cyclic voltammetry measurements.…”

mentioning

confidence: 99%

Investigation of the High Electron Affinity Molecular Dopant F6‐TCNNQ for Hole‐Transport Materials

Zhang

Kahn

2017

Adv Funct Materials

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2,2′-(perfluoronaphthalene-2,6-diylidene)dimalononitrile (F6-TCNNQ) is investigated as a molecular p-type dopant in two hole-transport materials, 2,2′,7,7′-tetrakis(N,N-diphenylamino)-9,9-spirobifluorene (Spiro-TAD) and tris(4-carbazoyl-9-ylphenyl)amine (TCTA). The electron affinity of F6-TCNNQ is determined to be 5.60 eV, one of the strongest organic molecular oxidizing agents used to date in organic electronics. p-Doping is found to be effective in Spiro-TAD (ionization energy = 5.46 eV) but not in TCTA (ionization energy = 5.85 eV). Optical absorption measurements demonstrate that charge transfer is the predominant doping mechanism in Spiro-TAD:F6-TCNNQ. The hostdopant interaction also leads to a significant alteration of the host film morphology. Finally, transport measurements done on Spiro-TAD:F6-TCNNQ as a function of dopant concentration and temperature, and using a highly doped contact layer to ensure negligible hole injection barrier, lead to an accurate measurement of the film conductivity and hole-hopping activation energy.

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Determination of electron affinity of electron accepting molecules

Cited by 115 publications

References 16 publications

Fine-Tuning the Electrostatic Properties of an Alkali-Linked Organic Adlayer on a Metal Substrate

Fine-Tuning the Electrostatic Properties of an Alkali-Linked Organic Adlayer on a Metal Substrate

Competition between the Charge Transfer State and the Singlet States of Donor or Acceptor Limiting the Efficiency in Polymer:Fullerene Solar Cells

Investigation of the High Electron Affinity Molecular Dopant F6‐TCNNQ for Hole‐Transport Materials

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