Conducting thin films of pentacene doped with alkaline metals

Minakata, Takashi; Ozaki, Masaru; Imai, Hideaki

doi:10.1063/1.354955

Cited by 67 publications

(43 citation statements)

References 13 publications

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“…1, DOS approximately resembles the undoped bands in this case. The possibility of spin polarization is marginal for this structural model (see Table I structure is energetically unlikely, perhaps the detailed way in which samples are grown matters and could eventually explain metallic behavior [10,11,14]. In any case, as said previously, interlayer doping is limited to one electron (K atom) per pentacene molecule.…”

Section: A Kpentacene Compoundmentioning

confidence: 99%

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Structural and electronic changes of pentacene induced by potassium doping

Guijarro

Vergés

2017

Phys. Rev. B

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Potassium is introduced into the crystalline herringbone structure of pentacene searching for a compound showing metallic electronic transport properties and, hopefully, superconductivity at small enough temperatures. Several possible structures for stoichiometric KPentacene (1:1), K 2 Pentacene (2:1), and K 3 Pentacene (3:1) compounds are theoretically investigated. Detailed densities of states for all of them are presented. As a more prominent result, a new monoclinic structure has been stabilized for the potassium richer material that could correspond to the recently synthesized superconducting phase of K 3 Pentacene. Although energetically unfavorable, it is the only metallic candidate found to date.

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Section: A Kpentacene Compoundmentioning

confidence: 99%

“…Results given in Refs. [10,11,14] could be understood in this context. On the other hand, additional experimental results point to a prompt metal-insulator transition at the first stages of doping [15][16][17].…”

Section: A Kpentacene Compoundmentioning

confidence: 99%

Structural and electronic changes of pentacene induced by potassium doping

Guijarro

Vergés

2017

Phys. Rev. B

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“…These results were slightly modified [10], but yielded both a characteristic d(0 0 1) value of 14.4 A . In 1991, Minakata et al reported on the growth and crystal structure of thin films [11,12]. They reported for thin films d(0 0 1) spacings of 15.0 and 15.4 A .…”

Section: Introductionmentioning

confidence: 99%

“…In the literature, different d(0 0 l) values are reported for pentacene thin films [4,11,12,19]. To investigate this, we have grown thin films of pentacene, using different growth conditions.…”

Section: Growth Of the Different Polymorphs On Thin Filmsmentioning

confidence: 99%

Identification of polymorphs of pentacene

et al. 2003

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Pentacene crystallizes in a layered structure with a herringbone arrangement within the layers. The electronic properties depend strongly on the stacking of the molecules within the layers [J. Phys. Chem. B. 106 (2002) . Single crystals commonly adopt the 14.1 A structure, whereas all four polymorphs can be synthesized in thin film form, depending on growth conditions. We have identified part of the unit cell parameters of these polymorphs by X-ray and electron diffraction (ED). The 15.0 and 15.4 A polymorphs transform at elevated temperature to the 14.1 and 14.4 A polymorphs, respectively. Using SCLC measurements, we determined the mobility of the 14.1 A polymorph to be 0.2 cm 2 /V s at room temperature. #

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“…Bulk KxPentacene (x = 1, 2 and 3.6) has previously been reported without structural characterisation, [17][18][19] and metallic conductivity has been reported in potassium-doped pentacene thin films. [20][21][22][23][24] As pentacene is more readily available than picene, we chose initially to address the synthesis of potassium-intercalated pentacene samples suitable for structural analysis, before applying these protocols to the picene system. …”

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confidence: 99%

Redox-controlled potassium intercalation into two polyaromatic hydrocarbon solids

et al. 2017

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Alkali metal intercalation into polyaromatic hydrocarbons (PAHs) has been studied intensely following reports of superconductivity in a number of potassium-and rubidium-intercalated materials. There are however no reported crystal structures to inform understanding of the chemistry and physics because of the complex reactivity of PAHs with strong reducing agents at high temperature. Here we present the synthesis of crystalline K2Pentacene and K2Picene by a solid-solid insertion protocol that uses potassium hydride as a redox-controlled reducing agent to access the PAH dianions, enabling determination of their crystal structures. In both cases, the inserted cations expand the parent herringbone packings by reorienting the molecular anions to create multiple potassium sites within initially dense molecular layers, and thus interact with the PAH anion π-systems. The synthetic and crystal chemistry of alkali metal intercalation into PAHs differs from that into fullerenes and graphite, where the cation sites are pre-defined by the host structure.Reaction of alkali and alkaline earth metals with carbon-based molecular solids has been extensively studied in the search for novel magnetic and electronic properties, with a particular focus on superconductivity. [1][2][3][4][5][6] For example, alkali metal intercalation into solid C60 produces A3C60 superconductors, with Tc as high as 38 K for Cs3C60 at 7 kbar. 6 In these materials, cations occupy the interstitial voids that already exist in the host e.g., in the fcc lattice of C60 (Figure 1). 7 Reaction of potassium with picene (C22H14), a phenacene composed of five fused benzene rings, has been reported to afford superconductivity at 18 K. 8 Superconductivity in other alkali-metal polyaromatic hydrocarbons (PAHs) was subsequently reported in phenanthrene-, dibenzopentacene-and coronene-based materials, with the highest reported Tc of 33 K claimed 2 in potassium-doped 1,2:8,9-dibenzopentacene. [9][10][11] Despite the significant interest in these materials, to date no crystal structure has been determined for any of the alkali-metal PAH systems. This structural information is a prerequisite for materials design and for understanding of both physical properties and reaction chemistry.Picene, like many other PAHs (including molecules such as phenanthrene 12 which is reported to afford superconductivity on cation insertion), crystallises in the herringbone structure, 13 with layers consisting of two parallel one-dimensional chains of molecules with opposing inclinations defined by an intermolecular angle, ω, of 57.89(7)° (Supplementary Figure 1). 14 The largest voids in the structure are located between the picene layers, adjacent to the saturated C-H bonds and far from the electron density of the PAH π-systems ( Figure 1a). This contrasts with C60, where the octahedral and tetrahedral voids in the fcc lattice are adjacent to the conjugated π-electron system (Figure 1b Pentacene is the linear isomer of picene, and also adopts the herringbone structure, 16 with ω = 52...

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Conducting thin films of pentacene doped with alkaline metals

Abstract: Electrical properties of highly ordered and amorphous thin films of pentacene doped with iodine

Cited by 67 publications

References 13 publications

Structural and electronic changes of pentacene induced by potassium doping

Structural and electronic changes of pentacene induced by potassium doping

Identification of polymorphs of pentacene

Redox-controlled potassium intercalation into two polyaromatic hydrocarbon solids

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