1
|
Miyata R, Inoue S, Nikaido K, Nakajima K, Hasegawa T. Friction Force Mapping of Molecular Ordering and Mesoscopic Phase Transformations in Layered-Crystalline Organic Semiconductor Films. ACS APPLIED MATERIALS & INTERFACES 2024; 16:39701-39707. [PMID: 39013158 DOI: 10.1021/acsami.4c05169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/18/2024]
Abstract
It is critical to understand molecular ordering processes in small-molecule organic semiconductor (OSC) films in optimizing electronic device applications, although it is difficult to observe and investigate the ordering characteristics at a mesoscopic or device scale. Here, we report that friction force microscopy (FFM) allows visualizing the ordering transformation process from a thermodynamically metastable phase to a stable phase at a mesoscopic scale. We utilized 2-octyl-benzothieno[3,2-b]naphtho[2,3-b]thiophene (2-C8-BTNT) as a typical highly layered-crystalline OSC. We found that the friction force between an AFM tip and spin-coated OSC films significantly depends on whether local film states are in metastable monolayer phase or stable bilayer-type herringbone (b-LHB) phase that exhibits high carrier mobility. The formation of the stable b-LHB phase leads to lower friction than the metastable monolayer phase, clearly visualizing the molecular order. Force map (Fmap) analysis indicates that the lower friction in the b-LHB phase should be associated with the reduction of interfacial adhesion force. Notably, the observed results demonstrate that the spin-coated thin film changes from continuous film with the monolayer phase to rugged microcrystal grains with the b-LHB phase when left at ambient conditions. By contrast, an appropriate post-thermal annealing process facilitates the phase transformation without inducing such morphological changes. The technique provides a unique and effective tool for revealing the relationship between processing conditions and device performance in polycrystalline OSC films.
Collapse
Affiliation(s)
- Ryo Miyata
- Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
| | - Satoru Inoue
- Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
| | - Kiyoshi Nikaido
- Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
| | - Ken Nakajima
- Department of Chemical Science and Engineering, School of Materials and Chemical Technology, Tokyo Institute of Technology, Tokyo 152-8552, Japan
| | - Tatsuo Hasegawa
- Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
| |
Collapse
|
2
|
Wang CI, Maier JC, Jackson NE. Accessing the electronic structure of liquid crystalline semiconductors with bottom-up electronic coarse-graining. Chem Sci 2024; 15:8390-8403. [PMID: 38846409 PMCID: PMC11151863 DOI: 10.1039/d3sc06749a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Accepted: 05/01/2024] [Indexed: 06/09/2024] Open
Abstract
Understanding the relationship between multiscale morphology and electronic structure is a grand challenge for semiconducting soft materials. Computational studies aimed at characterizing these relationships require the complex integration of quantum-chemical (QC) calculations, all-atom and coarse-grained (CG) molecular dynamics simulations, and back-mapping approaches. However, these methods pose substantial computational challenges that limit their application to the requisite length scales of soft material morphologies. Here, we demonstrate the bottom-up electronic coarse-graining (ECG) of morphology-dependent electronic structure in the liquid-crystal-forming semiconductor, 2-(4-methoxyphenyl)-7-octyl-benzothienobenzothiophene (BTBT). ECG is applied to construct density functional theory (DFT)-accurate valence band Hamiltonians of the isotropic and smectic liquid crystal (LC) phases using only the CG representation of BTBT. By bypassing the atomistic resolution and its prohibitive computational costs, ECG enables the first calculations of the morphology dependence of the electronic structure of charge carriers across LC phases at the ∼20 nm length scale, with robust statistical sampling. Kinetic Monte Carlo (kMC) simulations reveal a strong morphology dependence on zero-field charge mobility among different LC phases as well as the presence of two-molecule charge carriers that act as traps and hinder charge transport. We leverage these results to further evaluate the feasibility of developing mesoscopic, field-based ECG models in future works. The fully CG approach to electronic property predictions in LC semiconductors opens a new computational direction for designing electronic processes in soft materials at their characteristic length scales.
Collapse
Affiliation(s)
- Chun-I Wang
- Department of Chemistry, University of Illinois at Urbana-Champaign 505 S Mathews Avenue Urbana Illinois 61801 USA
| | - J Charlie Maier
- Department of Chemistry, University of Illinois at Urbana-Champaign 505 S Mathews Avenue Urbana Illinois 61801 USA
| | - Nicholas E Jackson
- Department of Chemistry, University of Illinois at Urbana-Champaign 505 S Mathews Avenue Urbana Illinois 61801 USA
| |
Collapse
|
3
|
Yan S, Cornil D, Cornil J, Beljonne D, Palacios-Rivera R, Ocal C, Barrena E. Polar Polymorphism: A New Intermediate Structure toward the Thin-Film Phase in Asymmetric Benzothieno[3,2- b][1]-benzothiophene Derivatives. CHEMISTRY OF MATERIALS : A PUBLICATION OF THE AMERICAN CHEMICAL SOCIETY 2024; 36:585-595. [PMID: 38222937 PMCID: PMC10783425 DOI: 10.1021/acs.chemmater.3c02926] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/16/2023] [Revised: 12/11/2023] [Accepted: 12/11/2023] [Indexed: 01/16/2024]
Abstract
Understanding structure and polymorphism is relevant for any organic device optimization, and it is of particular relevance in 7-decyl-2-phenyl[1]benzothieno[3,2-b][1]benzothiophene (Ph-BTBT-10) since high carrier mobility in Ph-BTBT-10 thin films has been linked to the structural transformation from the metastable thin-film phase to the thermodynamically stable bilayer structure via thermal annealing. We combine here a systematic nanoscale morphological analysis with local Kelvin probe force microcopy (KPFM) that demonstrates the formation of a polar polymorph in thin films as an intermediate structure for thicknesses lower than 20 nm. The polar structure develops with thickness a variable amount of structural defects in the form of individual flipped molecules (point defects) or sizable polar domains, and evolves toward the reported nonpolar thin-film phase. The direct experimental evidence is supported by electronic structure density functional theory calculations. The structure of the film has dramatic effects on the electronic properties, leading to a decrease in the film work function (by up to 1 eV) and a considerable broadening of the occupied molecular orbitals, attributed to electrostatic disorder. From an advanced characterization point of view, KPFM stands out as a valuable tool for evaluating electrostatic disorder and the conceivable emergence of polar polymorphs in organic thin films. The emergence of polar assemblies introduces a critical consideration for other asymmetric BTBT derivatives, which may be pivotal to understanding the structure-property relationships in organic field-effect transistors (OFETs). A precise determination of any polar assemblies close to the dielectric interface is critical for the judicious design and upgrading of high-performance OFETs.
Collapse
Affiliation(s)
- Shunya Yan
- Instituto
de Ciencia de Materiales de Barcelona (ICMAB-CSIC), Campus UAB, Bellaterra, E-08193 Barcelona, Spain
| | - David Cornil
- Laboratory
for Chemistry of Novel Materials, University
of Mons (UMONS), 20 Place du Parc, 7000 Mons, Belgium
| | - Jérôme Cornil
- Laboratory
for Chemistry of Novel Materials, University
of Mons (UMONS), 20 Place du Parc, 7000 Mons, Belgium
| | - David Beljonne
- Laboratory
for Chemistry of Novel Materials, University
of Mons (UMONS), 20 Place du Parc, 7000 Mons, Belgium
| | - Rogger Palacios-Rivera
- Instituto
de Ciencia de Materiales de Barcelona (ICMAB-CSIC), Campus UAB, Bellaterra, E-08193 Barcelona, Spain
| | - Carmen Ocal
- Instituto
de Ciencia de Materiales de Barcelona (ICMAB-CSIC), Campus UAB, Bellaterra, E-08193 Barcelona, Spain
| | - Esther Barrena
- Instituto
de Ciencia de Materiales de Barcelona (ICMAB-CSIC), Campus UAB, Bellaterra, E-08193 Barcelona, Spain
| |
Collapse
|
4
|
James AM, McIntosh N, Devaux F, Brocorens P, Cornil J, Greco A, Maini L, Pandey P, Pandolfi L, Kunert B, Venuti E, Geerts YH, Resel R. Polymorph screening at surfaces of a benzothienobenzothiophene derivative: discovering new solvate forms. MATERIALS HORIZONS 2023; 10:4415-4422. [PMID: 37476933 DOI: 10.1039/d3mh00764b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/22/2023]
Abstract
The discovery of new polymorphs opens up unique applications for molecular materials since their physical properties are predominantly influenced by the crystal structure type. The deposition of molecules at surfaces offers great potential in the variation of the crystallization conditions, thereby allowing access to unknown polymorphs. With our surface crystallization approach, four new phases are found for an oligoethylene glycol-benzothienobenzothiophene molecule, and none of these phases could be identified via classical polymorph screening. The corresponding crystal lattices of three of the new phases were obtained via X-ray diffraction (XRD). Based on the volumetric considerations together with X-ray fluorescence and Raman spectroscopy data, the phases are identified as solvates containing one, two or three solvent molecules per molecule. The strong interaction of dichloromethane with the oligoethylene glycol side chains of the molecules may be responsible for the formation of the solvates. Temperature-dependent XRD reveals the low thermal stability of the new phases, contrary to the thermodynamically stable bulk form. Nevertheless, the four solvates are stable under ambient conditions for at least two years. This work illustrates that defined crystallization at surfaces enables access to multiple solvates of a given material through precise and controlled variations in the crystallization kinetics.
Collapse
Affiliation(s)
- Ann Maria James
- Institute of Solid State Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria.
| | - Nemo McIntosh
- Laboratory for Chemistry of Novel Materials, University of Mons, 7000 Mons, Belgium
| | - Félix Devaux
- Laboratoire de Chimie des Polymères, Université Libre de Bruxelles (ULB), 1050 Bruxelles, Belgium
| | - Patrick Brocorens
- Laboratory for Chemistry of Novel Materials, University of Mons, 7000 Mons, Belgium
| | - Jérôme Cornil
- Laboratory for Chemistry of Novel Materials, University of Mons, 7000 Mons, Belgium
| | | | - Lucia Maini
- Dipartimento di Chimica "G. Ciamician", University Bologna, 40126 Bologna, Italy
| | - Priya Pandey
- Dipartimento di Chimica "G. Ciamician", University Bologna, 40126 Bologna, Italy
| | - Lorenzo Pandolfi
- Dipartimento di Chimica Industriale "Toso Montanari", Università di Bologna viale del Risorgimento, 4, 40136, Bologna, Italy
| | - Birgit Kunert
- Institute of Solid State Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria.
| | - Elisabetta Venuti
- Dipartimento di Chimica Industriale "Toso Montanari", Università di Bologna viale del Risorgimento, 4, 40136, Bologna, Italy
| | - Yves Henri Geerts
- Laboratoire de Chimie des Polymères, Université Libre de Bruxelles (ULB), 1050 Bruxelles, Belgium
- International Solvay Institutes of Physics and Chemistry, Université Libre de Bruxelles, 1050 Bruxelles, Belgium
| | - Roland Resel
- Institute of Solid State Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria.
| |
Collapse
|
5
|
Shioya N, Yoshida M, Fujii M, Shimoaka T, Miura R, Maruyama S, Hasegawa T. Conformational Change of Alkyl Chains at Phase Transitions in Thin Films of an Asymmetric Benzothienothiophene Derivative. J Phys Chem Lett 2022; 13:11918-11924. [PMID: 36525547 DOI: 10.1021/acs.jpclett.2c03399] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Among many promising organic semiconducting materials, 2-decyl-7-phenyl[1]benzothieno[3,2-b][1]benzothiophene (Ph-BTBT-C10) shows outstanding device performances for organic field-effect transistors. This compound has a highly ordered liquid crystalline state, i.e., the smectic E (SmE) phase. Although the transition from the crystalline state to the SmE phase is believed to accompany melting of the alkyl chains, no spectroscopic evidence has been found so far. In this study, the conformational change of the decyl chains in Ph-BTBT-C10 films across the phase transition is analyzed by temperature-dependent measurements in situ using infrared spectroscopy. The spectral analysis reveals that the polycrystalline film has latent conformational disorder (the gauche conformer), the rate of which becomes more pronounced with the heat treatment. As expected, melting of the decyl chains is observed above the transition temperature to the SmE phase. This study also highlights the discovery of some key bands sensitive to the phase transitions in liquid crystalline organic semiconductors.
Collapse
Affiliation(s)
- Nobutaka Shioya
- Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
| | - Mariko Yoshida
- Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
| | - Masamichi Fujii
- Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
| | - Takafumi Shimoaka
- Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
| | - Riku Miura
- Department of Applied Chemistry, Tohoku University, 6-6-07 Aramaki Aza Aoba, Aoba-ku, Sendai 980-8579, Japan
| | - Shingo Maruyama
- Department of Applied Chemistry, Tohoku University, 6-6-07 Aramaki Aza Aoba, Aoba-ku, Sendai 980-8579, Japan
| | - Takeshi Hasegawa
- Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
| |
Collapse
|