Structural, optical, and electronic characterization of perfluorinated sexithiophene films and mixed films with sexithiophene

Reisz, Berthold; Weimer, Simon; Banerjee, Rupak; Zeiser, Clemens; Lorch, Christopher; Duva, Giuliano; Dieterle, Johannes; Yonezawa, Koichi; Yang, Jinpeng; Ueno, Nobuo; Kera, Satoshi; Hinderhofer, Alexander; Gerlach, Alexander; Schreiber, Frank

doi:10.1557/jmr.2017.99

Cited by 10 publications

(11 citation statements)

References 77 publications

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“…Whether organic thin films become rougher or smoother on heated substrates is dependent on many parameters, such as the deposition rate (Storzer et al, 2017;Farahzadi et al, 2010) and the chemical structure (Belova et al, 2018;Reisz et al, 2017). Furthermore, the roughness depends on the film thickness and the choice of substrate (Dü rr et al, 2003;Kowarik et al, 2006;Yim & Jones, 2006;Hong et al, 2008;Zhang et al, 2009Zhang et al, , 2011Kim et al, 2010;Hinderhofer et al, 2011;Obaidulla & Giri, 2015;Nahm & Engstrom, 2016;Brillante et al, 2017;Chiodini, Straub et al, 2020).…”

Section: Discussionmentioning

confidence: 99%

Polymorphism and structure formation in copper phthalocyanine thin films

et al. 2021

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Many polymorphic crystal structures of copper phthalocyanine (CuPc) have been reported over the past few decades, but despite its manifold applicability, the structure of the frequently mentioned α polymorph remained unclear. The base-centered unit cell (space group C2/c) suggested in 1966 was ruled out in 2003 and was replaced by a primitive triclinic unit cell (space group P 1). This study proves unequivocally that both α structures coexist in vacuum-deposited CuPc thin films on native silicon oxide by reciprocal space mapping using synchrotron radiation in grazing incidence. The unit-cell parameters and the space group were determined by kinematic scattering theory and provide possible molecular arrangements within the unit cell of the C2/c structure by excluded-volume considerations. In situ X-ray diffraction experiments and ex situ atomic force microscopy complement the experimental data further and provide insight into the formation of a smooth thin film by a temperature-driven downward diffusion of CuPc molecules during growth.

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Section: Discussionmentioning

confidence: 99%

Polymorphism and structure formation in copper phthalocyanine thin films

et al. 2021

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“…Therefore, the study of anisotropic properties in thin films of OSCs is highly relevant for devices. Examples of uniaxially anisotropic optical properties in thin films of molecular semiconductors have been reported in refs. − In these studies, the focus has been kept mainly on the optical anisotropy of one-component films, for which transitions at energies equal or above the fundamental gap (typically around 2 eV) were investigated. In heterostructures with D/A character, intermolecular interactions can give rise to several new optical transitions located below the band gap of the pristine materials.…”

Section: Introductionmentioning

confidence: 99%

Thin-Film Texture and Optical Properties of Donor/Acceptor Complexes. Diindenoperylene/F6TCNNQ vs Alpha-Sexithiophene/F6TCNNQ

et al. 2018

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In this work, two novel donor/acceptor (D/A) complexes, namely, diindenoperylene (DIP)/1,3,4,5,7,8-hexafluoro-tetracyanonaphthoquinodimethane (F6TCNNQ) and alpha-sexithiophene (6T)/F6TCNNQ, are studied. The D/A complexes segregate in form of π–π stacked D/A cocrystals and can be observed by X-ray scattering. The different conformational degrees of freedom of the donor molecules, respectively, seem to affect the thin-film crystalline texture and composition of the D/A mixtures significantly. In equimolar mixtures, for DIP/F6TCNNQ, the crystallites are mostly uniaxially oriented and homogeneous, whereas for 6T/F6TCNNQ, a mostly 3D (isotropic) orientation of the crystallites and coexistence of domains of pristine compounds and D/A complex, respectively, are observed. Using optical absorption spectroscopy, we observe for each of the two mixed systems a set of new, strong transitions located in the near-IR range below the gap of the pristine compounds: such transitions are related to charge-transfer (CT) interactions between donor and acceptor. The optical anisotropy of domains of the D/A complexes with associated new electronic states is studied by ellipsometry. We infer that the CT-related transition dipole moment is perpendicular to the respective π-conjugated planes in the D/A complex.

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“…The data reported in Figure g,h represents nevertheless a qualitative estimation of the optical anisotropy. Because the HOMO–LUMO TDM of 6T is parallel to the long molecular axis, k z is larger than k xy for the 6T film in σ-orientation and vice versa for the 6T film in σ-orientation. However, the optical anisotropy for the 6T film in λ-orientation is weaker than that for DIP in λ-orientation, which we ascribe to the higher mosaicity in 6T.…”

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confidence: 97%

Template-Free Orientation Selection of Rod-Like Molecular Semiconductors in Polycrystalline Films

Duva

Mann

Pithan

et al. 2019

J. Phys. Chem. Lett.

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Many organic semiconductors (OSCs) feature strong optical anisotropy that can be exploited to increase the efficiency of optoelectronic devices. We demonstrate that for the technologically relevant, rod-like OSCs diindenoperylene (DIP), pentacene (PEN), and α-sexithiophene (6T) deposited on silicon oxide surfaces it is possible to prepare polycrystalline thin films in which the long molecular axis is oriented parallel to the substrate plane in a template-free fashion. In films grown by organic molecular beam deposition at room temperature or higher, the molecules are oriented upright standing (σ-orientation). Instead, the here-presented growth at low temperatures followed by slow annealing up to a temperature near molecular desorption has the effect of “freezing” the molecules with their long axis oriented parallel to the substrate plane (λ-orientation) while conferring them crystalline long-range order. We discuss the huge impact on the optical anisotropy of the films observed as a consequence of the orientation transition. Finally, we propose a mechanism for explaining the achieved λ-orientation, which is stable under environmental conditions.

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Structural, optical, and electronic characterization of perfluorinated sexithiophene films and mixed films with sexithiophene

Abstract: Abstract

Cited by 10 publications

References 77 publications

Polymorphism and structure formation in copper phthalocyanine thin films

Polymorphism and structure formation in copper phthalocyanine thin films

Thin-Film Texture and Optical Properties of Donor/Acceptor Complexes. Diindenoperylene/F6TCNNQ vs Alpha-Sexithiophene/F6TCNNQ

Template-Free Orientation Selection of Rod-Like Molecular Semiconductors in Polycrystalline Films

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