Dopant controlled trap-filling and conductivity enhancement in an electron-transport polymer

Higgins, Andrew; Mohapatra, Swagat K.; Barlow, Stephen; Marder, Seth R.; Kahn, Antoine

doi:10.1063/1.4918627

Cited by 59 publications

(57 citation statements)

References 31 publications

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“…[52] This coupling of electron-transfer and bond-cleavage processes results in materials that are moderately air stable, despite their strongly reducing character. Both of these compounds have been used as dopants for organic semiconductors [53][54][55] and for reducing the work function of oxide electrodes. [56,57] Pentamethylrhodocene dimer has also been recently demonstrated to dope SLG, causing the work function to decrease by 1.29 eV.…”

Section: Ev)mentioning

confidence: 99%

Facile Doping and Work‐Function Modification of Few‐Layer Graphene Using Molecular Oxidants and Reductants

Mansour

Said

Dey

et al. 2017

Adv Funct Materials

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Doping of graphene is a viable route towards enhancing its electrical conductivity and modulating its work function for a wide range of technological applications. In this work, we demonstrate facile, solution-based, non-covalent surface doping of few-layer graphene (FLG) using a series of molecular metal-organic and organic species of varying n-and p-type doping strengths. In doing so we tune the electronic, optical and transport properties of FLG. We modulate the work function of graphene over a range of 2.4 eV (from 2.9 to 5.3 eV) -unprecedented for solution-based doping -via surface electron transfer. A substantial improvement of the conductivity of FLG is attributed to increasing carrier density, slightly offset by a minor reduction of mobility via Coulomb scattering. The mobility of single layer graphene has been reported to decrease significantly more via similar surface doping than FLG, which has the ability to screen buried layers. The dopant dosage influences the properties of FLG and reveals an optimal window of dopant coverage for the best transport 2 properties, wherein dopant molecules aggregate into small and isolated clusters on the surface of FLG. This study shows how soluble molecular dopants can easily and effectively tune the work function and improve the optoelectronic properties of graphene.

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Section: Ev)mentioning

confidence: 99%

Facile Doping and Work‐Function Modification of Few‐Layer Graphene Using Molecular Oxidants and Reductants

Mansour

Said

Dey

et al. 2017

Adv Funct Materials

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“…11,12 Nevertheless a few stable n-type dopants have been reported via mechanisms other than integer charge transfer. [13][14][15][16][17][18][19][20][21][22][23][24][25] For example the addition of 1H-benzimidazole or benzimidazolium salts has succeeded in tuning of the work function of graphene and the conductivity of fullerene derivatives. 13,26 Mechanistic studies in the solution phase found that the dopant reacted with the fullerene derivative through hydride or hydrogen atom transfer to afford host radical anions, which were responsible for the doping effect.…”

Section: Introductionmentioning

confidence: 99%

Anion-induced N-doping of naphthalenediimide polymer semiconductor in organic thin-film transistors

et al. 2018

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Molecular doping is an important strategy to improve the charge transport properties of organic semiconductors in various electronic devices. Compared to p-type dopants, the development of n-type dopants is especially challenging due to poor dopant stability against atmospheric conditions. In this article, we report the n-doping of the milestone naphthalenediimide-based conjugated polymer P(NDI2OD-T2) in organic thin film transistor devices by soluble anion dopants. The addition of the dopants resulted in the formation of stable radical anions in thin films, as confirmed by EPR spectroscopy. By tuning the dopant concentration via simple solution mixing, the transistor parameters could be readily controlled. Hence the contact resistance between the electrodes and the semiconducting polymer could be significantly reduced, which resulted in the transistor behaviour approaching the desirable gate voltage-independent model. Reduced hysteresis was also observed, thanks to the trap filling by the dopant. Under optimal doping concentrations the channel on-current was increased several fold whilst the on/off ratio was simultaneously increased by around one order of magnitude. Hence doping with soluble organic salts appears to be a promising route to improve the charge transport properties of n-type organic semiconductors.

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“…Additionally, the symmetric gold-organic-gold structure ensures that there is no built-in potential in the measured device. Finally, we introduce a new procedure to resolve the problem of the electrode-organic injection barrier, [32] and form Ohmic contacts in the planar structure, without which the Ohmic region of the I-V characteristics cannot be accessed. The lack of ohmicity is clearly shown with the black curve of Figure 7b, which corresponds to the current obtained using Au only as the hole-injection contact for Spiro-TAD.…”

Section: Introductionmentioning

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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Dopant controlled trap-filling and conductivity enhancement in an electron-transport polymer

Cited by 59 publications

References 31 publications

Facile Doping and Work‐Function Modification of Few‐Layer Graphene Using Molecular Oxidants and Reductants

Facile Doping and Work‐Function Modification of Few‐Layer Graphene Using Molecular Oxidants and Reductants

Anion-induced N-doping of naphthalenediimide polymer semiconductor in organic thin-film transistors

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

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