Supramolecular Ordering of PTCDA Molecules: The Key Role of Dispersion Forces in an Unusual Transition from Physisorbed into Chemisorbed State

Godlewski, Szymon; Tekiel, Antoni; Piskorz, Witold; Zasada, Filip; Prauzner‐Bechcicki, Jakub S.; Sojka, Zbigniew; Szymoński, Marek

doi:10.1021/nn303546m

Cited by 50 publications

(70 citation statements)

References 62 publications

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“…6,7 Ahead of an impressive increase of the number of newly synthesized PTCDI derivatives for both OPVs 8 and OFETs, 9 the advanced modeling of perylenes is mostly focused on the intermolecular coupling geometry, 10 which affects the optical spectrum, 11 and on the structure of monolayer phases at surfaces. [12][13][14] From the experimental point of view, the spectroscopic characterization of the molecular orbitals of the free PTCDI molecule, as well as of perylene, is largely outdated or limited. [15][16][17][18] In this context, the knowledge of the molecular orbital symmetry and energy, as measured in NEXAFS, is fundamental to understand the key parameters that govern the performances of an archetypal device, such as the orientation of the molecules on the surfaces 19 and the mechanism of charge transfer to the substrate.…”

Section: Introductionmentioning

confidence: 99%

High resolution NEXAFS of perylene and PTCDI: a surface science approach to molecular orbital analysis

Fratesi

Lanzilotto

Stranges

et al. 2014

Phys. Chem. Chem. Phys.

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We made use of synchrotron radiation to perform near edge X-ray absorption fine structure spectroscopy, NEXAFS, at the carbon K-edge of perylene and perylene-tetracarboxylic-diimide, PTCDI. Reference spectra measured for isolated molecules in the gas phase are compared with polarization dependent NEXAFS spectra measured on highly oriented thin films in order to study the symmetry of the molecular orbitals. The molecular overlayers are grown onto the rutile TiO 2 (110) surface for which the large anisotropic corrugation effectively drives the molecular orientation, while its dielectric nature prevents the rehybridization of the molecular orbitals. We employed density functional theory, DFT, calculations to disentangle the contribution of specific carbon atoms to the molecular density of states. Numerical simulations correctly predict the observed NEXAFS azimuthal dichroism of the s* resonances above the ionization threshold, from which we determine the full geometric orientation of the overlayer molecules. A discrepancy observed for the spectral contribution of the imide carbon atom to the calculated unoccupied molecular orbitals has been explained in terms of initial state effects, as determined by Hartree-Fock corrections and in full agreement with the corresponding shift of the C 1s core level measured by X-ray photoelectron spectroscopy, XPS.

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Section: Introductionmentioning

confidence: 99%

High resolution NEXAFS of perylene and PTCDI: a surface science approach to molecular orbital analysis

Fratesi

Lanzilotto

Stranges

et al. 2014

Phys. Chem. Chem. Phys.

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“…[44][45][46] In the second case, PTCDA molecules present a flat lying geometry on the surface. 43 Our calculations 18 for the two cases show different properties: while the tilted geometry has a weak interaction with the surface, the flat geometry develops a stronger one, with a significant molecular distortion. The interface energy level alignment is very sensitive to the adsorption geometry: the flat geometry presents a much larger interface dipole potential (1.7 eV) than the tilted case (0.3 eV), due to a larger charge transfer between the molecule and the oxide.…”

Section: Results For Different Organic Molecules (Ptcda Zn-tpp and Tmentioning

confidence: 85%

“…Recent works 42,43 have proposed two likely candidates for PTCDA adsorption on TiO 2 (110). In one case, PTCDA molecules are adsorbed on the oxide surface lying along one of their long sides in a tilted geometry, see Figure 2, in similarity to the cases of PTCDI, perylene or pentacene.…”

Section: Results For Different Organic Molecules (Ptcda Zn-tpp and Tmentioning

confidence: 99%

Unveiling universal trends for the energy level alignment in organic/oxide interfaces

Martínez

Ortega

Rangan

et al. 2017

Phys. Chem. Chem. Phys.

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In this perspective we present a comprehensive analysis of the energy level alignment at the interface between an organic monolayer (organic = perylenetetracarboxylic dianhydride, PTCDA, zinc tetraphenylporphyrin, Zn-TPP, and tetracyanoquinodimethane, TCNQ) and a prototypical oxide surface, TiO 2 (110), looking for universal behaviours. PTCDA shows a physisorbed interaction with TiO 2 and a small interface dipole potential with its highest occupied molecular orbital (HOMO) energy level located in the oxide energy gap and the lowest occupied molecular orbital (LUMO) energy level located above the oxide conduction band minimum, E C . We analyse how the interface barrier depends on an external bias potential between the organic layer and the oxide surface, Δ, and find for this interface that the screening parameter S = d|(E C -HOMO)|dΔ is close to 1. In the second case, the Zn-TPP monolayer shows a moderate chemisorbed interaction with some charge transfer from the molecule to the oxide and a significant interface dipole potential, in such a way that S decreases to around 0.8. In the TCNQ/TiO 2 (110) case, the TCNQ molecules present a strong chemical interaction with the oxide; the LUMO energy level is located in the oxide energy gap in such a way that one electron is transferred from the oxide to the organic molecule; we also find that in this case S ≈ 0.5. All these cases can be integrated within a universal behaviour when (E C -HOMO) is calculated as a function of Δ; that function presents a zig-zag curve with a central part having an S-slope, and two plateaus associated with either the LUMO or the HOMO energy levels crossing the oxide Fermi level. In these plateaus, a Coulomb blockade regime arises and a space charge layer develops in the oxide surface.

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“…Additionally, ordering of the molecules in the layers is shown to vary from a slightly tilted geometry, to a disordered one, and to a nearly flat-lying geometry as the coverage density increases from the submonolayer to monolayer, and to multilayer regimes [29]. These results can be confronted with scanning tunnelling microscopy studies discussing the influence of dispersion forces on the supramolecular ordering of the molecules in a layer described by Godlewski et al [28]. These authors have shown that at a low coverage, below 0.7 ML, molecules form poorly ordered layers of physisorbed species.…”

Section: Reviewmentioning

confidence: 99%

Scanning probe microscopy studies on the adsorption of selected molecular dyes on titania

Prauzner‐Bechcicki¹,

Zając²,

Olszowski³

et al. 2016

Beilstein J. Nanotechnol.

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Titanium dioxide, or titania, sensitized with organic dyes is a very attractive platform for photovoltaic applications. In this context, the knowledge of properties of the titania–sensitizer junction is essential for designing efficient devices. Consequently, studies on the adsorption of organic dyes on titania surfaces and on the influence of the adsorption geometry on the energy level alignment between the substrate and an organic adsorbate are necessary. The method of choice for investigating the local environment of a single dye molecule is high-resolution scanning probe microscopy. Microscopic results combined with the outcome of common spectroscopic methods provide a better understanding of the mechanism taking place at the titania–sensitizer interface. In the following paper, we review the recent scanning probe microscopic research of a certain group of molecular assemblies on rutile titania surfaces as it pertains to dye-sensitized solar cell applications. We focus on experiments on adsorption of three types of prototypical dye molecules, i.e., perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA), phtalocyanines and porphyrins. Two interesting heteromolecular systems comprising molecules that are aligned with the given review are discussed as well.

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Supramolecular Ordering of PTCDA Molecules: The Key Role of Dispersion Forces in an Unusual Transition from Physisorbed into Chemisorbed State

Cited by 50 publications

References 62 publications

High resolution NEXAFS of perylene and PTCDI: a surface science approach to molecular orbital analysis

High resolution NEXAFS of perylene and PTCDI: a surface science approach to molecular orbital analysis

Unveiling universal trends for the energy level alignment in organic/oxide interfaces

Scanning probe microscopy studies on the adsorption of selected molecular dyes on titania

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