Impact of molecular tilt angle on the absorption spectra of pentacene:perfluoropentacene blends

Broch, Katharina; Bürker, Christoph; Dieterle, Johannes; Krause, Stefan; Gerlach, Alexander; Schreiber, Frank

doi:10.1002/pssr.201308085

Cited by 8 publications

(7 citation statements)

References 58 publications

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“…• Phase separation: If the two materials are sterically incompatible [62] or the interaction energies within the single materials are significantly more attractive than the inter-species energy (χ > 2) usually a phase separation of the materials is observed. • Ordered complex: An ordered complex is usually formed if the interaction energy between the two different materials is higher than the interaction energies within one species and the materials are sterically compatible [61,63,64].…”

Section: Phase Separation In Bhj Geometriesmentioning

confidence: 99%

Charge Separation at Nanostructured Molecular Donor–Acceptor Interfaces

Opitz

Banerjee

Grob

et al. 2016

Elementary Processes in Organic Photovoltaics

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Section: Phase Separation In Bhj Geometriesmentioning

confidence: 99%

Charge Separation at Nanostructured Molecular Donor–Acceptor Interfaces

Opitz

Banerjee

Grob

et al. 2016

Elementary Processes in Organic Photovoltaics

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“…19 Moreover, the accompanying theoretical analysis of the fluorine NEXAFS spectra, carried out within the framework of the transition potential method, has actually yielded a mixed π*/σ* character, which in turn hampers a quantitative analysis of the F 1s dichroism in pure and mixed systems. 19,20 In their study Oteyza et al used monolayer films of PFCuPc and PFP adsorbed on noble metals. 19 While this approach provides planar adsorption geometries in general, it remains a priori unclear whether the NEXAFS signature is affected by electronic adsorbate-substrate coupling.…”

Section: ■ Introductionmentioning

confidence: 99%

“…In a previous study of PFCuPc and perfluorinated pentacene (PFP) inversed dichroisms have been reported for the carbon and fluorine K-edge NEXAFS signatures . Moreover, the accompanying theoretical analysis of the fluorine NEXAFS spectra, carried out within the framework of the transition potential method, has actually yielded a mixed π*/σ* character, which in turn hampers a quantitative analysis of the F 1s dichroism in pure and mixed systems. , …”

Section: Introductionmentioning

confidence: 99%

Understanding the F 1s NEXAFS Dichroism in Fluorinated Organic Semiconductors

Klues¹,

Jerabek²,

Breuer³

et al. 2016

J. Phys. Chem. C

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The analysis of NEXAFS spectra acquired at the absorption edge of heteroatoms like fluorine, nitrogen, or oxygen enables the determination of the molecular orientation of individual compounds even in multinary structures. Such an analysis requires detailed knowledge about the nature of the corresponding electronic excitations, especially because 1s-π* and 1s-σ* excitations frequently feature disparate transition dipole moments in planar molecules. Unlike intuitively assumed, the resulting dichroisms of both excitation types in planar systems are, however, not necessarily inverted. Instead, both the structure of the molecules and their alignment on the substrate determine the actual dichroisms. In this study, the NEXAFS signature and dichroisms of thin films of the organic n-type semiconductor perfluoropentacene (PFP) in different crystalline orientations at the carbon and fluorine absorption K-edge are thoroughly analyzed. For lying molecular orientations, an inverted dichroism at the fluorine K-edge compared to the carbon K-edge is found. In contrast, for upright molecular configurations the dichroisms at both absorption edges are similar. With the help of density functional theory methods, this behavior is explained by the different nature of the excitations. While at the carbon K-edge 1s-π* excitations are most prominent, 1s-σ*-related signals are dominant at the fluorine K-edge. Computations of the NEXAFS signatures and corresponding excitations at different levels of theory are compared with particular focus on electronic relaxation. Energetic positions and oscillator strengths, especially for resonances of σ*-type, depend strongly on the theoretical approach whereas the π*-related signals are barely affected by the methods applied in the present work. Similar effects were also found for the analysis of the smaller perfluoronaphthalene and are explained by the different relaxation effects for 1s-σ*- and 1s-π*-type excitations. As the investigated acenes are representative model systems for π-conjugated molecular semiconductors, the present findings are important for the understanding of the electronic properties and the application of NEXAFS for structural analysis in such materials

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“…This result coincides with that obtained by Raman spectroscopy. The absorption spectra of pentacene films also exhibit the same phenomena (see Supporting Information, Figure S4); that is, the red shift is observed in the curves of FOS films as the growth temperature increases and the trend of the curve shift of neat pentacene films is reverse. This similar result shows that the interaction of electron coupling in FOS films must be influenced by the doping of Ni atoms.…”

Section: Results and Discussionmentioning

confidence: 60%

Ferromagnetism above Room Temperature in a Ni-Doped Organic-Based Magnetic Semiconductor

Chou

Peng

Chang

et al. 2021

ACS Appl. Mater. Interfaces

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Ferromagnetic semiconductors with structural flexibility are an indispensable feature for future flexible spin-electronic applications. In this case, we introduce magnetic ingredients into an organic semiconductor, namely, pentacene, to form a ferromagnetic organic semiconductor (FOS). The first observation for ferromagnetic Ni-doped pentacene semiconductors at room temperature in the field of semiconductor spintronics is reported in this article. To date, the mechanism of FOSs with ferromagnetism is not understood yet, especially when their Curie temperature is enhanced above room temperature. Here, we demonstrate dopants of Ni atoms and the modulation of the growth temperature in the FOS films to achieve room-temperature ferromagnetic properties in a series of FOS films, one of which has a maximum coercivity of 257.6 Oe. The spin-exchange interaction between a Ni atom and a pentacene molecule is detected through the magnetic hysteresis obtained using a superconducting quantum interference device magnetometer. We verify the effectiveness of this spin coupling through magnetic force microscopy, Raman spectroscopy, scanning Kelvin probe microscopy, and theoretical simulation. A model for the indirect spin coupling between Ni atoms is proposed for the mechanism of room-temperature ferromagnetic ordering of spins due to the exchange force indirectly. We believe that the π-electrons of pentacene molecules at the triple state for this model can support the spin coupling of electrons of Ni atoms. Our findings facilitate the development of brand-new spintronic devices with structural flexibility and room-temperature ferromagnetism.

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Impact of molecular tilt angle on the absorption spectra of pentacene:perfluoropentacene blends

Cited by 8 publications

References 58 publications

Charge Separation at Nanostructured Molecular Donor–Acceptor Interfaces

Charge Separation at Nanostructured Molecular Donor–Acceptor Interfaces

Understanding the F 1s NEXAFS Dichroism in Fluorinated Organic Semiconductors

Ferromagnetism above Room Temperature in a Ni-Doped Organic-Based Magnetic Semiconductor

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