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Werkovits A, Hollweger SB, Niederreiter M, Risse T, Cartus JJ, Sterrer M, Matera S, Hofmann OT. Kinetic Trapping of Charge-Transfer Molecules at Metal Interfaces. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2024; 128:3082-3089. [PMID: 38414835 PMCID: PMC10895664 DOI: 10.1021/acs.jpcc.3c08262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Revised: 01/23/2024] [Accepted: 01/24/2024] [Indexed: 02/29/2024]
Abstract
Despite the common expectation that conjugated organic molecules on metals adsorb in a flat-lying layer, several recent studies have found coverage-dependent transitions to upright-standing phases, which exhibit notably different physical properties. In this work, we argue that from an energetic perspective, thermodynamically stable upright-standing phases may be more common than hitherto thought. However, for kinetic reasons, this phase may often not be observed experimentally. Using first-principles kinetic Monte Carlo simulations, we find that the structure with lower molecular density is (almost) always formed first, reminiscent of Ostwald's rule of stages. The phase transitions to the upright-standing phase are likely to be kinetically hindered under the conditions typically used in surface science. The simulation results are experimentally confirmed for the adsorption of tetracyanoethylene on Cu(111) using infrared and X-ray photoemission spectroscopy. Investigating both the role of the growth conditions and the energetics of the interface, we find that the time for the phase transition is determined mostly by the deposition rate and, thus, is mostly independent of the nature of the molecule.
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Affiliation(s)
- Anna Werkovits
- Institute
of Solid State Physics, Graz University of Technology, Petersgasse 16/II, 8010 Graz, Austria
| | - Simon B. Hollweger
- Institute
of Solid State Physics, Graz University of Technology, Petersgasse 16/II, 8010 Graz, Austria
| | - Max Niederreiter
- Institute
of Physics, University of Graz, Universitätsplatz 5, 8010 Graz, Austria
| | - Thomas Risse
- Institut
für Chemie und Biochemie, Freie Universität Berlin, Arminallee 22, 14195 Berlin, Germany
| | - Johannes J. Cartus
- Institute
of Solid State Physics, Graz University of Technology, Petersgasse 16/II, 8010 Graz, Austria
| | - Martin Sterrer
- Institute
of Physics, University of Graz, Universitätsplatz 5, 8010 Graz, Austria
| | - Sebastian Matera
- Theory
Department, Fritz Haber Institute of the
MPG, Faradayweg 4-6, 14195 Berlin-Dahlem, Germany
| | - Oliver T. Hofmann
- Institute
of Solid State Physics, Graz University of Technology, Petersgasse 16/II, 8010 Graz, Austria
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2
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Stroet M, Sanderson S, Sanzogni AV, Nada S, Lee T, Caron B, Mark AE, Burn PL. PyThinFilm: Automated Molecular Dynamics Simulation Protocols for the Generation of Thin Film Morphologies. J Chem Inf Model 2023; 63:2-8. [PMID: 36539938 DOI: 10.1021/acs.jcim.2c01334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The performance of organic optoelectronic devices, such as organic light-emitting diodes (OLEDs) and organic solar cells (OSCs), is intrinsically related to the molecular-scale morphology of the thin films from which they are composed. However, the experimental characterization of morphology at the molecular level is challenging due to the often amorphous or at best semicrystalline nature of these films. Classical molecular modeling techniques, such as molecular dynamics (MD) simulation, are increasingly used to understand the relationship between morphology and the properties of thin-film devices. PyThinFilm (github.com/ATB-UQ/PyThinFilm) is an open-source Python package which allows fully automated MD simulations of thin film growth to be performed using vacuum and/or solution deposition processes. PyThinFilm utilizes the GROMACS simulation package in combination with interaction parameters from the Automated Topology Builder (atb.uq.edu.au). Here, PyThinFilm is described along with an overview of applications in which PyThinFilm has been used to study the thin films of organic semiconductor materials typically used in OLEDs and OSCs.
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Affiliation(s)
- Martin Stroet
- Centre for Organic Photonics & Electronics, The University of Queensland, St Lucia Campus, Brisbane, Queensland4072, Australia.,Molecular Dynamics Group, School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia Campus, Brisbane, Queensland4072, Australia
| | - Stephen Sanderson
- The Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, St Lucia Campus, Brisbane, Queensland4072, Australia.,College of Science and Engineering, James Cook University, Townsville, Queensland4811, Australia
| | - Audrey V Sanzogni
- Centre for Organic Photonics & Electronics, The University of Queensland, St Lucia Campus, Brisbane, Queensland4072, Australia.,Molecular Dynamics Group, School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia Campus, Brisbane, Queensland4072, Australia
| | - Sharif Nada
- Molecular Dynamics Group, School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia Campus, Brisbane, Queensland4072, Australia
| | - Thomas Lee
- Centre for Organic Photonics & Electronics, The University of Queensland, St Lucia Campus, Brisbane, Queensland4072, Australia.,Molecular Dynamics Group, School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia Campus, Brisbane, Queensland4072, Australia
| | - Bertrand Caron
- Molecular Dynamics Group, School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia Campus, Brisbane, Queensland4072, Australia
| | - Alan E Mark
- Molecular Dynamics Group, School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia Campus, Brisbane, Queensland4072, Australia
| | - Paul L Burn
- Centre for Organic Photonics & Electronics, The University of Queensland, St Lucia Campus, Brisbane, Queensland4072, Australia
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3
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Controlling morphology and microstructure of conjugated polymers via solution-state aggregation. Prog Polym Sci 2022. [DOI: 10.1016/j.progpolymsci.2022.101626] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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4
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Empting E, Bader N, Oettel M. Interplay of orientational order and roughness in simulated thin film growth of anisotropically interacting particles. Phys Rev E 2022; 105:045306. [PMID: 35590594 DOI: 10.1103/physreve.105.045306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Accepted: 03/29/2022] [Indexed: 06/15/2023]
Abstract
Roughness and orientational order in thin films of anisotropic particles are investigated using kinetic Monte Carlo simulations on a cubic lattice. Anisotropic next-neighbor interactions between the lattice particles were chosen to mimic the effects of shape anisotropy in the interactions of disk- or rodlike molecules with van der Waals attractions. Increasing anisotropy leads first to a preferred orientation in the film (which is close to the corresponding equilibrium transition) while the qualitative mode of roughness evolution (known from isotropic systems) does not change. At strong anisotropies, an effective step-edge (Ehrlich-Schwoebel) barrier appears and a nonequilibrium roughening effect is found, accompanied by reordering in the film which can be interpreted as the nucleation and growth of domains of lying-down disks or rods. The information on order and roughness is combined into a diagram of dynamic growth modes.
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Affiliation(s)
- E Empting
- Institut für Angewandte Physik, Universität Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
| | - N Bader
- Institut für Angewandte Physik, Universität Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
| | - M Oettel
- Institut für Angewandte Physik, Universität Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
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5
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Boehm BJ, Huang DM. A simple predictor of interface orientation of fluids of disk-like anisotropic particles and its implications for organic semiconductors. SOFT MATTER 2022; 18:1843-1857. [PMID: 35169825 DOI: 10.1039/d2sm00026a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
From classical molecular dynamics simulations, we identify a simple and general predictor of molecular orientation at solid and vapour interfaces of isotropic fluids of disk-like anisotropic particles based on their shape and interaction anisotropy. For a wide variety of inter-particle interactions, temperatures, and substrate types within the range of typical organic semiconductors and their processing conditions, we find remarkable universal scaling of the orientation at the interface with the free energy calculated from pair interactions between close-packed nearest neighbours and an empirically derived universal relationship between the entropy and the shape anisotropy and bulk volume fraction of the fluid particles. The face-on orientation of fluid particles at the solid interface is generally predicted to be the equilibrium structure, although the alignment can be controlled by tuning the particle shape and substrate type, while changing the strength of fluid-fluid interactions is likely to play a less effective role. At the vapour interface, only the side-on structure is predicted, and conditions for which the face-on structure may be preferred, such as low temperature, low interaction anisotropy, or low shape anisotropy, are likely to result in little orientation preference (due to the low anisotropy) or be associated with a phase transition to an anisotropic bulk phase for systems with interactions in the range of typical organic semiconductors. Based on these results, we propose a set of guidelines for the rational design and processing of organic semiconductors to achieve a target orientation at a solid or vapour interface.
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Affiliation(s)
- Belinda J Boehm
- Department of Chemistry, School of Physical Sciences, The University of Adelaide, Adelaide, Australia.
| | - David M Huang
- Department of Chemistry, School of Physical Sciences, The University of Adelaide, Adelaide, Australia.
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6
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Werkovits A, Jeindl A, Hörmann L, Cartus JJ, Hofmann OT. Toward Targeted Kinetic Trapping of Organic–Inorganic Interfaces: A Computational Case Study. ACS PHYSICAL CHEMISTRY AU 2022; 2:38-46. [PMID: 35098244 PMCID: PMC8796281 DOI: 10.1021/acsphyschemau.1c00015] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Revised: 09/21/2021] [Accepted: 09/23/2021] [Indexed: 11/29/2022]
Abstract
![]()
Properties of inorganic–organic interfaces, such as their
interface dipole, strongly depend on the structural arrangements of
the organic molecules. A prime example is tetracyanoethylene (TCNE)
on Cu(111), which shows two different phases with significantly different
work functions. However, the thermodynamically preferred phase is
not always the one that is best suited for a given application. Rather,
it may be desirable to selectively grow a kinetically trapped structure.
In this work, we employ density functional theory and transition state
theory to discuss under which conditions such a kinetic trapping might
be possible for the model system of TCNE on Cu. Specifically, we want
to trap the molecules in the first layer in a flat-lying orientation.
This requires temperatures that are sufficiently low to suppress the
reorientation of the molecules, which is thermodynamically more favorable
for high dosages, but still high enough to enable ordered growth through
diffusion of molecules. On the basis of the temperature-dependent
diffusion and reorientation rates, we propose a temperature range
at which the reorientation can be successfully suppressed.
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Affiliation(s)
- Anna Werkovits
- Institute of Solid State Physics, TU Graz, NAWI Graz, Petersgasse 16/II, 8010 Graz, Austria
| | - Andreas Jeindl
- Institute of Solid State Physics, TU Graz, NAWI Graz, Petersgasse 16/II, 8010 Graz, Austria
| | - Lukas Hörmann
- Institute of Solid State Physics, TU Graz, NAWI Graz, Petersgasse 16/II, 8010 Graz, Austria
| | - Johannes J. Cartus
- Institute of Solid State Physics, TU Graz, NAWI Graz, Petersgasse 16/II, 8010 Graz, Austria
| | - Oliver T. Hofmann
- Institute of Solid State Physics, TU Graz, NAWI Graz, Petersgasse 16/II, 8010 Graz, Austria
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7
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Chen X, Fonseca I, Ravnik M, Slastikov V, Zannoni C, Zarnescu A. Topics in the mathematical design of materials. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2021; 379:20200108. [PMID: 34024134 DOI: 10.1098/rsta.2020.0108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 03/29/2021] [Indexed: 06/12/2023]
Abstract
We present a perspective on several current research directions relevant to the mathematical design of new materials. We discuss: (i) design problems for phase-transforming and shape-morphing materials, (ii) epitaxy as an approach of central importance in the design of advanced semiconductor materials, (iii) selected design problems in soft matter, (iv) mathematical problems in magnetic materials, (v) some open problems in liquid crystals and soft materials and (vi) mathematical problems on liquid crystal colloids. The presentation combines topics from soft and hard condensed matter, with specific focus on those design themes where mathematical approaches could possibly lead to exciting progress. This article is part of the theme issue 'Topics in mathematical design of complex materials'.
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Affiliation(s)
- Xian Chen
- Department of Mechanical and Aerospace Engineering, Hong Kong University of Science and Technology, Pokfulam, Hong Kong
| | - Irene Fonseca
- Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213, USA
| | - Miha Ravnik
- University of Ljubljana, Jadranska, 19, 1000 Ljubljana, Slovenia
- Jozef Stefan Insitute, Jamova cesta, 39, 1000 Ljubljana, Slovenia
| | | | - Claudio Zannoni
- Dipartimento di Chimica Industriale 'Toso Montanari' and INSTM, Università di Bologna, Viale Risorgimento, 4, 40136 Bologna, Italy
| | - Arghir Zarnescu
- BCAM, Basque Center for Applied Mathematics, Alameda Mazarredo, 14 Bilbao 48009, Spain
- IKERBASQUE, Basque Foundation for Science, Plaza Euskadi, 5 48009 Bilbao, Bizkaia, Spain
- 'Simion Stoilow' Institute of the Romanian Academy, 21 Calea Grivitei, 010702 Bucharest, Romania
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8
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Empting E, Klopotek M, Hinderhofer A, Schreiber F, Oettel M. Lattice gas study of thin-film growth scenarios and transitions between them: Role of substrate. Phys Rev E 2021; 103:023302. [PMID: 33736115 DOI: 10.1103/physreve.103.023302] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Accepted: 01/17/2021] [Indexed: 11/07/2022]
Abstract
Thin-film growth is investigated in two types of lattice gas models where substrate and film particles are different, expressed by unequal interaction energy parameters. The first is of solid-on-solid type, whereas the second additionally incorporates desorption, diffusion in the gas phase above the film and readsorption at the film (appropriate for growth in colloidal systems). In both models, the difference between particle-substrate and particle-particle interactions plays a central role for the evolution of the film morphology at intermediate times. The models exhibit a dynamic layering transition which occurs at generally lower substrate attraction strengths than the equilibrium layering transition. A second, flattening transition is found where initial island growth transforms to layer-by-layer growth at intermediate deposition times. Combined with the known roughening behavior in such models for very large deposition times, we present four global growth scenarios, charting out the possible types of roughness evolution.
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Affiliation(s)
- E Empting
- Institut für Angewandte Physik, Universität Tübingen, 72076 Tübingen, Germany
| | - M Klopotek
- Institut für Angewandte Physik, Universität Tübingen, 72076 Tübingen, Germany
| | - A Hinderhofer
- Institut für Angewandte Physik, Universität Tübingen, 72076 Tübingen, Germany
| | - F Schreiber
- Institut für Angewandte Physik, Universität Tübingen, 72076 Tübingen, Germany
| | - M Oettel
- Institut für Angewandte Physik, Universität Tübingen, 72076 Tübingen, Germany
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9
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De Nicola A, Correa A, Giunchi A, Muccioli L, D'Avino G, Kido J, Milano G. Bidimensional H‐Bond Network Promotes Structural Order and Electron Transport in BPyMPMs Molecular Semiconductor. ADVANCED THEORY AND SIMULATIONS 2021. [DOI: 10.1002/adts.202000302] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Antonio De Nicola
- Frontier Center for Organic Materials (FROM) Yamagata University 4‐3‐16 Jonan Yonezawa Yamagata 992‐8510 Japan
| | - Andrea Correa
- Dipartment of Chemistry University of Naples Federico II Complesso di Monte S. Angelo Napoli 80126 Italy
| | - Andrea Giunchi
- Department of Industrial Chemistry “Toso Montanari” University of Bologna Bologna 40136 Italy
| | - Luca Muccioli
- Department of Industrial Chemistry “Toso Montanari” University of Bologna Bologna 40136 Italy
| | - Gabriele D'Avino
- Grenoble Alpes University CNRS Grenoble INP Institut Néel 25 Rue des Martyrs Grenoble 38042 France
| | - Junji Kido
- Frontier Center for Organic Materials (FROM) Yamagata University 4‐3‐16 Jonan Yonezawa Yamagata 992‐8510 Japan
| | - Giuseppe Milano
- Frontier Center for Organic Materials (FROM) Yamagata University 4‐3‐16 Jonan Yonezawa Yamagata 992‐8510 Japan
- Department of Chemistry and Biology “Adolfo Zambelli” University of Salerno Fisciano 84084 Italy
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10
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Londi G, Khan SUZ, Muccioli L, D'Avino G, Rand BP, Beljonne D. Fate of Low-Lying Charge-Transfer Excited States in a Donor:Acceptor Blend with a Large Energy Offset. J Phys Chem Lett 2020; 11:10219-10226. [PMID: 33206537 DOI: 10.1021/acs.jpclett.0c02858] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
In an effort to gain a comprehensive picture of the interfacial states in bulk heterojunction solar cells, we provide a combined experimental-theoretical analysis of the energetics and dynamics of low-lying electronic charge-transfer (CT) states in donor:acceptor blends with a large frontier orbital energy offset. By varying the blend composition and temperature, we unravel the static and dynamic contributions to the disordered density of states (DOS) of the CT-state manifold and assess their recombination to the ground state. Namely, we find that static disorder (conformational and electrostatic) shapes the CT DOS and that fast nonradiative recombination crops the low-energy tail of the distribution probed by external quantum efficiency (EQE) measurements (thereby largely contributing to voltage losses). Our results then question the standard practice of extracting microscopic parameters such as exciton energy and energetic disorder from EQE.
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Affiliation(s)
- Giacomo Londi
- Laboratory for Chemistry of Novel Materials, University of Mons, Place du Parc 20, 7000 Mons, Belgium
| | - Saeed-Uz-Zaman Khan
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | - Luca Muccioli
- Department of Industrial Chemistry, University of Bologna, Viale Risorgimento 4, 40136 Bologna, Italy
| | - Gabriele D'Avino
- Grenoble Alpes University, CNRS, Grenoble INP, Institut Néel, 25 rue des Martyrs, 38042 Grenoble, France
| | - Barry P Rand
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, United States
- Andlinger Center for Energy and the Environment, Princeton University, Princeton, New Jersey 08544, United States
| | - David Beljonne
- Laboratory for Chemistry of Novel Materials, University of Mons, Place du Parc 20, 7000 Mons, Belgium
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11
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Lee T, Sanzogni AV, Burn PL, Mark AE. Evolution and Morphology of Thin Films Formed by Solvent Evaporation: An Organic Semiconductor Case Study. ACS APPLIED MATERIALS & INTERFACES 2020; 12:40548-40557. [PMID: 32844643 DOI: 10.1021/acsami.0c08454] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The crucial role played by the solution-vapor interface in determining the growth and morphology of an organic semiconductor thin film formed by solvent evaporation has been examined in atomic detail. Specifically, how the loss of individual solvent molecules from the surface of the solution induces solute assembly has been studied using molecular dynamics simulations. The system consisted of bis(2-phenylpyridine) (acetylacetonate)iridium(III) [Ir(ppy)2(acac)] and 4,4'-bis(N-carbazolyl)-1,1'-biphenyl (CBP) in chloroform at 310 K. The simulations clearly indicate that (a) the system does not undergo uniform phase separation (spinodal decomposition), (b) solute aggregation initiates at the solution-vapor interface, (c) the distribution of solvent in the film is nonhomogeneous, (d) this nonhomogeneous distribution can induce preferential alignment of host molecules, and (e) a portion of the solvent likely remains trapped within the film. The work not only demonstrates the ability to directly model evaporation in atomic detail on the relevant length scales but also shows that atomistic simulations have the potential to shed new light on morphological properties of a wide range of organic semiconductor devices manufactured using solution-processing methods.
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Affiliation(s)
- Thomas Lee
- School of Chemistry & Molecular Biosciences, The University of Queensland, St. Lucia Campus, Brisbane 4072, Australia
- Centre for Organic Photonics & Electronics, The University of Queensland, St. Lucia Campus, Brisbane 4072, Australia
| | - Audrey V Sanzogni
- School of Chemistry & Molecular Biosciences, The University of Queensland, St. Lucia Campus, Brisbane 4072, Australia
- Centre for Organic Photonics & Electronics, The University of Queensland, St. Lucia Campus, Brisbane 4072, Australia
| | - Paul L Burn
- School of Chemistry & Molecular Biosciences, The University of Queensland, St. Lucia Campus, Brisbane 4072, Australia
- Centre for Organic Photonics & Electronics, The University of Queensland, St. Lucia Campus, Brisbane 4072, Australia
| | - Alan E Mark
- School of Chemistry & Molecular Biosciences, The University of Queensland, St. Lucia Campus, Brisbane 4072, Australia
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12
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Silvestri F, Prieto MJ, Babuji A, Tănase LC, de Souza Caldas L, Solomeshch O, Schmidt T, Ocal C, Barrena E. Impact of Nanomorphology on Surface Doping of Organic Semiconductors: The Pentacene-C 60F 48 Interface. ACS APPLIED MATERIALS & INTERFACES 2020; 12:25444-25452. [PMID: 32388975 DOI: 10.1021/acsami.0c05583] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Establishing the rather complex correlation between the structure and the charge transfer in organic-organic heterostructures is of utmost importance for organic electronics and requires spatially resolved structural, chemical, and electronic details. Insight into this issue is provided here by combining atomic force microscopy, Kelvin probe force microscopy, photoemission electron microscopy, and low-energy electron microscopy for investigating a case study. We select the interface formed by pentacene (PEN), benchmark among the donor organic semiconductors, and a p-type dopant from the family of fluorinated fullerenes. As for Buckminsterfullerene (C60), the growth of its fluorinated derivative C60F48 is influenced by the thickness and crystallinity of the PEN buffer layer, but the behavior is markedly different. We provide a microscopic description of the C60F48/PEN interface formation and analyze the consequences in the electronic properties of the final heterostructure. For just one single layer of PEN, a laterally complete but noncompact C60F48/PEN interface is created, importantly affecting the surface work function. Nonetheless, from the very beginning of the second layer formation, the presence of epitaxial and nonepitaxial PEN domains dramatically influences the growth dynamics and extremely well packed two-dimensional C60F48 islands develop. Insightful elemental maps of the C60F48/PEN surface spatially resolve the nonuniform distribution of the dopant molecules, which leads to a heterogeneous work function landscape.
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Affiliation(s)
- Francesco Silvestri
- Instituto de Ciencia de Materiales de Barcelona (ICMAB-CSIC), Bellaterra, 08193 Barcelona, Spain
| | - Mauricio J Prieto
- Department of Interface Science, Fritz-Haber Institute of the Max Planck Society, 14195 Berlin, Germany
| | - Adara Babuji
- Instituto de Ciencia de Materiales de Barcelona (ICMAB-CSIC), Bellaterra, 08193 Barcelona, Spain
| | - Liviu C Tănase
- Department of Interface Science, Fritz-Haber Institute of the Max Planck Society, 14195 Berlin, Germany
| | - Lucas de Souza Caldas
- Department of Interface Science, Fritz-Haber Institute of the Max Planck Society, 14195 Berlin, Germany
| | - Olga Solomeshch
- Electrical Engineering Department, Nanoelectronic Center, Technion, Haifa 32000, Israel
| | - Thomas Schmidt
- Department of Interface Science, Fritz-Haber Institute of the Max Planck Society, 14195 Berlin, Germany
| | - Carmen Ocal
- Instituto de Ciencia de Materiales de Barcelona (ICMAB-CSIC), Bellaterra, 08193 Barcelona, Spain
| | - Esther Barrena
- Instituto de Ciencia de Materiales de Barcelona (ICMAB-CSIC), Bellaterra, 08193 Barcelona, Spain
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13
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Boehm BJ, Nguyen HTL, Huang DM. The interplay of interfaces, supramolecular assembly, and electronics in organic semiconductors. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:423001. [PMID: 31212263 DOI: 10.1088/1361-648x/ab2ac2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Organic semiconductors, which include a diverse range of carbon-based small molecules and polymers with interesting optoelectronic properties, offer many advantages over conventional inorganic semiconductors such as silicon and are growing in importance in electronic applications. Although these materials are now the basis of a lucrative industry in electronic displays, many promising applications such as photovoltaics remain largely untapped. One major impediment to more rapid development and widespread adoption of organic semiconductor technologies is that device performance is not easily predicted from the chemical structure of the constituent molecules. Fundamentally, this is because organic semiconductor molecules, unlike inorganic materials, interact by weak non-covalent forces, resulting in significant structural disorder that can strongly impact electronic properties. Nevertheless, directional forces between generally anisotropic organic-semiconductor molecules, combined with translational symmetry breaking at interfaces, can be exploited to control supramolecular order and consequent electronic properties in these materials. This review surveys recent advances in understanding of supramolecular assembly at organic-semiconductor interfaces and its impact on device properties in a number of applications, including transistors, light-emitting diodes, and photovoltaics. Recent progress and challenges in computer simulations of supramolecular assembly and orientational anisotropy at these interfaces is also addressed.
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Affiliation(s)
- Belinda J Boehm
- Department of Chemistry, School of Physical Sciences, The University of Adelaide, SA 5005, Australia
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14
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Lorenzoni A, Muccini M, Mercuri F. A Computational Predictive Approach for Controlling the Morphology of Functional Molecular Aggregates on Substrates. ADVANCED THEORY AND SIMULATIONS 2019. [DOI: 10.1002/adts.201900156] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Andrea Lorenzoni
- Istituto per lo Studio dei Materiali Nanostrutturati (ISMN)Consiglio Nazionale delle Ricerche (CNR) Via P. Gobetti 101 40129 Bologna Italy
| | - Michele Muccini
- Istituto per lo Studio dei Materiali Nanostrutturati (ISMN)Consiglio Nazionale delle Ricerche (CNR) Via P. Gobetti 101 40129 Bologna Italy
| | - Francesco Mercuri
- Istituto per lo Studio dei Materiali Nanostrutturati (ISMN)Consiglio Nazionale delle Ricerche (CNR) Via P. Gobetti 101 40129 Bologna Italy
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15
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Huttner A, Breuer T, Witte G. Controlling Interface Morphology and Layer Crystallinity in Organic Heterostructures: Microscopic View on C 60 Island Formation on Pentacene Buffer Layers. ACS APPLIED MATERIALS & INTERFACES 2019; 11:35177-35184. [PMID: 31455082 DOI: 10.1021/acsami.9b09369] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Controlling the crystallinity of organic thin films is an important aspect in the improvement of organic electronic devices. However, because of high molecular mass, structural anisotropy, and weak intermolecular van der Waals bonding, crystalline ordering is not easily accomplished. While film preparation at elevated substrate temperature often improves the crystalline quality, this approach cannot be applied to temperature-sensitive materials such as plastic foils used as substrates for flexible electronics. Here, we examine in detail a low-temperature approach to improve film crystallinity by using ultrathin pentacene (PEN) buffer layers that allow crystalline growth of buckminsterfullerene (C60) thin films while without such buffer layers, only amorphous fullerene films are formed upon room-temperature deposition on various support substrates. Remarkably, this effect depends critically on the thickness of the PEN buffer and requires a thickness of at least two monolayers to induce crystalline growth, whereas a buffer layer consisting of a monolayer of PEN again yields amorphous C60 films. Combining crystallographic investigations by X-ray diffraction and atomic force microscopy measurements, we determine distinct nucleation sites on buffer layers of different thickness, which are correlated to the amorphous, respectively crystalline C60 islands. Our microscopic analysis reveals distinct differences for the nucleation and diffusivity of fullerenes on the PEN monolayer and on thicker buffer layers, which are attributed to the molecular arrangement in the PEN monolayer. Finally, we show that the crystalline C60 films are exclusively (111)-oriented and the fullerene islands are even heteroepitaxially aligned on the PEN buffer.
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Affiliation(s)
- Andrea Huttner
- Fachbereich Physik , Philipps-Universität Marburg , 35032 Marburg , Germany
| | - Tobias Breuer
- Fachbereich Physik , Philipps-Universität Marburg , 35032 Marburg , Germany
| | - Gregor Witte
- Fachbereich Physik , Philipps-Universität Marburg , 35032 Marburg , Germany
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16
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Lee TS, Lin YL, Kim H, Rand BP, Scholes GD. Two temperature regimes of triplet transfer in the dissociation of the correlated triplet pair after singlet fission. CAN J CHEM 2019. [DOI: 10.1139/cjc-2018-0421] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The ability to undergo spin-allowed exciton multiplication makes singlet fission materials promising for photovoltaic applications. Here, we examine the separation of correlated triplet pairs, 1(T…T), in polycrystalline pentacene films via temperature-dependent transient absorption spectroscopy. Single wavelength analysis reveals a profound delay in 1(T…T) dynamics. Moreover, the dynamics of 1(T…T) exhibit temperature dependence, whereas other features show no discernable temperature dependence. Previous literatures have suggested that correlated triplet separation is mediated by a thermally activated hopping process. Surprisingly, we found that the time constants governing triplet pair separation display two distinct temperature-dependent regimes of triplet transport. The high temperature regime follows a thermally activated hopping mechanism. The experimentally derived reorganization energy and electronic coupling is verified by density matrix renormalization group quantum chemical calculations. In addition, we evaluated the low temperature regime and show that the trend can be modelled by a Miller–Abrahams-type model that incorporates the effects of energetic disorder. We conclude that the correlated triplet pair separation is mediated by thermally activated hopping or a disorder driven Miller–Abrahams-type mechanism at high and low temperature, respectively. We observe that crossover between two regimes occurs ∼226 K. We find the time constant for triplet–triplet energy transfer to be 1.8 ps at ambient temperature and 21 ps at 77 K.
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Affiliation(s)
- Tia S. Lee
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
| | - YunHui L. Lin
- Department of Electrical Engineering, Princeton University, Princeton, NJ 08544, USA
| | - Hwon Kim
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
| | - Barry P. Rand
- Department of Electrical Engineering, Princeton University, Princeton, NJ 08544, USA
- Andlinger Center for Energy and the Environment, Princeton University, Princeton, NJ 08544, USA
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17
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Friederich P, Fediai A, Kaiser S, Konrad M, Jung N, Wenzel W. Toward Design of Novel Materials for Organic Electronics. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2019; 31:e1808256. [PMID: 31012166 DOI: 10.1002/adma.201808256] [Citation(s) in RCA: 57] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2018] [Indexed: 06/09/2023]
Abstract
Materials for organic electronics are presently used in prominent applications, such as displays in mobile devices, while being intensely researched for other purposes, such as organic photovoltaics, large-area devices, and thin-film transistors. Many of the challenges to improve and optimize these applications are material related and there is a nearly infinite chemical space that needs to be explored to identify the most suitable material candidates. Established experimental approaches struggle with the size and complexity of this chemical space. Herein, the development of simulation methods is addressed, with a particular emphasis on predictive multiscale protocols, to complement experimental research in the identification of novel materials and illustrate the potential of these methods with a few prominent recent applications. Finally, the potential of machine learning and methods based on artificial intelligence is discussed to further accelerate the search for new materials.
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Affiliation(s)
- Pascal Friederich
- Institute of Nanotechnology (INT), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany
- Department of Chemistry, University of Toronto, 80 St. George Street, M5S 3H6, Toronto, Ontario, Canada
| | - Artem Fediai
- Institute of Nanotechnology (INT), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany
| | - Simon Kaiser
- Institute of Nanotechnology (INT), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany
| | - Manuel Konrad
- Institute of Nanotechnology (INT), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany
| | - Nicole Jung
- Institute of Organic Chemistry (IOC), Karlsruhe Institute of Technology (KIT), Fritz-Haber-Weg 6, 76131, Karlsruhe, Germany
| | - Wolfgang Wenzel
- Institute of Nanotechnology (INT), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany
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18
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Affiliation(s)
- Tommaso Marcato
- Institute for Chemical and Bioengineering, Department of Chemistry and Applied BiosciencesETH Zürich Vladimir-Prelog-Weg 1–5/10 CH-8093 Zürich Switzerland
| | - Chih‐Jen Shih
- Institute for Chemical and Bioengineering, Department of Chemistry and Applied BiosciencesETH Zürich Vladimir-Prelog-Weg 1–5/10 CH-8093 Zürich Switzerland
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19
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Breuer T, Geiger T, Bettinger HF, Witte G. Diels-Alder adduct formation at solid interfaces between fullerenes and acenes. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:034003. [PMID: 30524049 DOI: 10.1088/1361-648x/aaf01b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Understanding organic-organic interfaces is rather challenging due to their large complexity regarding morphology, molecular orientation at the interface, interdiffusion, and energetics. One additional important but often neglected aspect are chemical reactions occuring at such interfaces. For solid interfaces between pentacene and Buckminster-Fullerene (C60) recently very efficient Diels-Alder (D-A) adduct formation has been reported. Considering the importance of pentacene/C60 as prototypical donor-acceptor combination to study fundamental processes in organic photovoltaics, understanding this effect is essential. In this work, we provide detailed NEXAFS-based investigations with respect to the temperature-dependence and reaction zone depth of this effect. Moreover, we widely vary the interface morphology and observe that the D-A adduct formation is most efficient for bulk heterojunctions of pentacene and C60. By also investigating further material combinations such as PEN/C60-PCBM and interfaces between C60 and functionalized acenes, we observe trends for the occurrence of the D-A adduct formation correlated with the different chemical properties of the involved compounds.
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Affiliation(s)
- T Breuer
- Department of Physics, Molekulare Festkörperphysik, Philipps-Universität Marburg, 35032, Marburg, Germany
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20
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Yoo D, Song H, Youn Y, Jeon SH, Cho Y, Han S. A molecular dynamics study on the interface morphology of vapor-deposited amorphous organic thin films. Phys Chem Chem Phys 2019; 21:1484-1490. [PMID: 30607407 DOI: 10.1039/c8cp05294h] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The interfaces between amorphous organic layers play an important role in the efficiency and lifetime of organic light emitting diodes (OLEDs). However, an atomistic understanding of the interface morphology is still poor. In this study, we theoretically investigate the interfacial structure of amorphous organic films using molecular dynamics simulations that mimic vapor-deposition processes. We find that molecularly sharp interfaces are formed by the vapor-deposition process as the interface thickness spans only a mono- or double-layer in terms of lie-down geometry. Interestingly, the interface is more diffusive into the upper layer due to asymmetric interdiffusion during the vapor-deposition process, which is well described by a simple random-walk model. Additionally, we investigate the change in the molecular orientation of interdiffused molecules, which is crucial for device performance.
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Affiliation(s)
- Dongsun Yoo
- Department of Materials Science and Engineering and Research Institute of Advanced Materials, Seoul National University, Seoul 08826, Korea.
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21
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Roscioni OM, D'Avino G, Muccioli L, Zannoni C. Pentacene Crystal Growth on Silica and Layer-Dependent Step-Edge Barrier from Atomistic Simulations. J Phys Chem Lett 2018; 9:6900-6906. [PMID: 30449102 DOI: 10.1021/acs.jpclett.8b03063] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Understanding and controlling the growth of organic crystals deposited from the vapor phase is important for fundamental materials science and necessary for applications in pharmaceutical and organic electronics industries. Here, this process is studied for the paradigmatic case of pentacene on silica by means of a specifically tailored computational approach inspired by the experimental vapor deposition process. This scheme is able to reproduce the early stages of the thin-film formation, characterized by a quasi layer-by-layer growth, thus showcasing its potential as a tool complementary to experimental techniques for investigating organic crystals. Crystalline islands of standing molecules are formed at a critical coverage, as a result of a collective reorientation of disordered aggregates of flat-lying molecules. The growth then proceeds by sequential attachment of molecules at the cluster and then terrace edges. Free-energy calculations allowed us to characterize the step-edge barrier for descending the terraces, a fundamental parameter for growth models for which only indirect experimental measurements are available. The barrier is found to be layer-dependent (approximately 1 kcal/mol for the first monolayer on silica, 2 kcal/mol for the second monolayer) and to extend over a distance comparable with the molecular length.
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Affiliation(s)
- Otello Maria Roscioni
- Dipartimento di Chimica Industriale "Toso Montanari" , University of Bologna , Viale Risorgimento 4 , I-40136 Bologna , Italy
| | - Gabriele D'Avino
- Institut Néel, CNRS and Grenoble Alpes University , 25 Rue des Martyrs , F-38042 Grenoble , France
| | - Luca Muccioli
- Dipartimento di Chimica Industriale "Toso Montanari" , University of Bologna , Viale Risorgimento 4 , I-40136 Bologna , Italy
| | - Claudio Zannoni
- Dipartimento di Chimica Industriale "Toso Montanari" , University of Bologna , Viale Risorgimento 4 , I-40136 Bologna , Italy
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22
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Olivier Y, Sancho-Garcia JC, Muccioli L, D'Avino G, Beljonne D. Computational Design of Thermally Activated Delayed Fluorescence Materials: The Challenges Ahead. J Phys Chem Lett 2018; 9:6149-6163. [PMID: 30265539 DOI: 10.1021/acs.jpclett.8b02327] [Citation(s) in RCA: 73] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Thermally activated delayed fluorescence (TADF) offers promise for all-organic light-emitting diodes with quantum efficiencies competing with those of transition-metal-based phosphorescent devices. While computational efforts have so far largely focused on gas-phase calculations of singlet and triplet excitation energies, the design of TADF materials requires multiple methodological developments targeting among others a quantitative description of electronic excitation energetics, fully accounting for environmental electrostatics and molecular conformational effects, the accurate assessment of the quantum mechanical interactions that trigger the elementary electronic processes involved in TADF, and a robust picture for the dynamics of these fundamental processes. In this Perspective, we describe some recent progress along those lines and highlight the main challenges ahead for modeling, which we hope will be useful to the whole TADF community.
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Affiliation(s)
- Y Olivier
- Laboratory for Chemistry of Novel Materials , University of Mons , Place du Parc 20 , B-7000 Mons , Belgium
| | - J-C Sancho-Garcia
- Departamento de Química Física , Universidad de Alicante , E-03080 Alicante , Spain
| | - L Muccioli
- Dipartimento di Chimica Industriale "Toso Montanari" , Università di Bologna , I-40136 Bologna , Italy
- Institut des Sciences Moléculaires, UMR 5255 , University of Bordeaux , F- 33405 Talence , France
| | - G D'Avino
- Institut Néel, CNRS and Grenoble Alpes University, F-38042 Grenoble , France
| | - D Beljonne
- Laboratory for Chemistry of Novel Materials , University of Mons , Place du Parc 20 , B-7000 Mons , Belgium
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23
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Lin JB, Jin Y, Lopez SA, Druckerman N, Wheeler SE, Houk KN. Torsional Barriers to Rotation and Planarization in Heterocyclic Oligomers of Value in Organic Electronics. J Chem Theory Comput 2017; 13:5624-5638. [DOI: 10.1021/acs.jctc.7b00709] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Janice B. Lin
- Department
of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States
| | - Yu Jin
- Department
of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States
| | - Steven A. Lopez
- Department
of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States
| | - Nathaniel Druckerman
- Department
of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States
| | - Steven E. Wheeler
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - K. N. Houk
- Department
of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States
- Department of Chemical and Biomolecular
Engineering, University of California, Los Angeles, California 90095, United States
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24
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Röthel C, Radziown M, Resel R, Grois A, Simbrunner C, Werzer O. Crystal alignment of caffeine deposited onto single crystal surfaces via hot-wall epitaxy. CrystEngComm 2017; 19:2936-2945. [PMID: 28670199 PMCID: PMC5471919 DOI: 10.1039/c7ce00515f] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Accepted: 04/27/2017] [Indexed: 01/09/2023]
Abstract
Crystal growth of caffeine on single crystalline surfaces yields needle or bird-like shaped crystals depending on surface chemistry and symmetry.
Defined crystal growth is highly demanded for technological applications but also fundamental research. Within this work, the crystal growth of the asymmetric molecule caffeine was studied on single crystalline surfaces of muscovite mica, sodium chloride and potassium chloride. While elongated needle-like crystals grow on muscovite mica and sodium chloride, smaller individual “bird-like” structures were observed on potassium chloride. Depending on the surface type and temperature, the disk-shaped caffeine molecules prefer either an edge-on or flat-on orientation with respect to the surface, but in each case, a defined crystallographic relation between the surface and caffeine crystallites was determined by using the X-ray pole figure technique. On muscovite mica and sodium chloride, needle-like crystallites with edge-on oriented molecules aligned mainly with the unit cell c-axis (which coincides with the long needle axis) along the [1–10]mica, [100]mica, [110]mica and [110]NaCl, [1–10]NaCl directions, respectively. Crystals consisting of flat-on oriented molecules on KCl showed also defined alignments with respect to the substrate, but due to the altered molecule–substrate contact, the b-axis aligned along [110]KCl and [1–10]KCl. Growth at elevated temperatures enabled changes in the crystal growth whereby more defined structures formed on NaCl. On KCl, the bird-like structures remained very similar, while caffeine on the mica surface at elevated temperatures resulted in even additional texture forming with the caffeine molecules now also favoring a flat-on orientation with respect to the surface. The systematic variation of various system parameters demonstrates how sensitive the growth behavior of caffeine on this variety of substrates is.
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Affiliation(s)
- Christian Röthel
- Institute of Pharmaceutical Sciences , Department of Pharmaceutical Technology , Karl-Franzens Universität Graz , Universitätsplatz 1 , 8010 Graz , Austria . ; .,Institute of Solid State Physics , Graz University of Technology , Petersgasse 16 , 8010 Graz , Austria
| | - Michal Radziown
- Institute of Semiconductor and Solid State Physics , Johannes Kepler Universität Linz , Altenbergerstraße 69 , 4040 Linz , Austria
| | - Roland Resel
- Institute of Solid State Physics , Graz University of Technology , Petersgasse 16 , 8010 Graz , Austria.,BioTechMed - Graz , Austria
| | - Andreas Grois
- Institute of Solid State Physics , Graz University of Technology , Petersgasse 16 , 8010 Graz , Austria
| | - Clemens Simbrunner
- Institute of Solid State Physics , Graz University of Technology , Petersgasse 16 , 8010 Graz , Austria.,Institute of Solid State Physics , University of Bremen , Otto-Hahn-Allee 1 , 28359 Bremen , Germany
| | - Oliver Werzer
- Institute of Pharmaceutical Sciences , Department of Pharmaceutical Technology , Karl-Franzens Universität Graz , Universitätsplatz 1 , 8010 Graz , Austria . ; .,BioTechMed - Graz , Austria
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25
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Miller RA, Larson A, Pohl K. Novel surface diffusion characteristics for a robust pentacene derivative on Au(1 1 1) surfaces. Chem Phys Lett 2017. [DOI: 10.1016/j.cplett.2017.04.018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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26
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Roscioni OM, Muccioli L, Zannoni C. Predicting the Conditions for Homeotropic Anchoring of Liquid Crystals at a Soft Surface. 4-n-Pentyl-4'-cyanobiphenyl on Alkylsilane Self-Assembled Monolayers. ACS APPLIED MATERIALS & INTERFACES 2017; 9:11993-12002. [PMID: 28287693 DOI: 10.1021/acsami.6b16438] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We have studied, using atomistic molecular dynamics simulations, the alignment of the nematic liquid-crystal 4-n-pentyl-4'-cyanobiphenyl (5CB) on self-assembled monolayers (SAMs) formed from octadecyl- and/or hexyltrichlorosilane (OTS and HTS) attached to glassy silica. We find a planar alignment on OTS at full coverage and an intermediate situation at partial OTS coverage because of the penetration of 5CB molecules into the monolayer, which also removes the tilt of the OTS SAM. Binary mixtures of HTS and OTS SAMs instead induce homeotropic (i.e., perpendicular) alignment. A comparison with the existing experimental literature is provided.
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Affiliation(s)
- Otello Maria Roscioni
- Dipartimento di Chimica Industriale "Toso Montanari" Università di Bologna , viale Risorgimento 4, IT-40136 Bologna, Italy
| | - Luca Muccioli
- Dipartimento di Chimica Industriale "Toso Montanari" Università di Bologna , viale Risorgimento 4, IT-40136 Bologna, Italy
| | - Claudio Zannoni
- Dipartimento di Chimica Industriale "Toso Montanari" Università di Bologna , viale Risorgimento 4, IT-40136 Bologna, Italy
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27
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Klopotek M, Hansen-Goos H, Dixit M, Schilling T, Schreiber F, Oettel M. Monolayers of hard rods on planar substrates. II. Growth. J Chem Phys 2017; 146:084903. [DOI: 10.1063/1.4976308] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- M. Klopotek
- Institut für Angewandte Physik, Eberhard Karls Universität Tübingen, D–72076 Tübingen, Germany
| | - H. Hansen-Goos
- Institut für Theoretische Physik, Eberhard Karls Universität Tübingen, D–72076 Tübingen, Germany
| | - M. Dixit
- Theory of Soft Condensed Matter, Physics and Materials Sciences Research Unit, Université du Luxembourg L-1511 Luxembourg, Luxembourg
| | - T. Schilling
- Theory of Soft Condensed Matter, Physics and Materials Sciences Research Unit, Université du Luxembourg L-1511 Luxembourg, Luxembourg
| | - F. Schreiber
- Institut für Angewandte Physik, Eberhard Karls Universität Tübingen, D–72076 Tübingen, Germany
| | - M. Oettel
- Institut für Angewandte Physik, Eberhard Karls Universität Tübingen, D–72076 Tübingen, Germany
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28
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Li SB, Geng Y, Duan YA, Sun GY, Zhang M, Qiu YQ, Su ZM. Theoretical study on the charge transfer mechanism at donor/acceptor interface: Why TTF/TCNQ is inadaptable to photovoltaics? J Chem Phys 2016; 145:244705. [DOI: 10.1063/1.4972005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- Shuang-Bao Li
- Institute of Functional Material Chemistry, Faculty of Chemistry, Northeast Normal University, Changchun 130024, People’s Republic of China
| | - Yun Geng
- Institute of Functional Material Chemistry, Faculty of Chemistry, Northeast Normal University, Changchun 130024, People’s Republic of China
| | - Yu-Ai Duan
- Department of Chemistry, Capital Normal University, Beijing 100048, People’s Republic of China
| | - Guang-Yan Sun
- Department of Chemistry, Faculty of Science, Yanbian University, Yanji 133002, People’s Republic of China
| | - Min Zhang
- Institute of Functional Material Chemistry, Faculty of Chemistry, Northeast Normal University, Changchun 130024, People’s Republic of China
| | - Yong-Qing Qiu
- Institute of Functional Material Chemistry, Faculty of Chemistry, Northeast Normal University, Changchun 130024, People’s Republic of China
| | - Zhong-Min Su
- Department of Chemistry, Faculty of Science, Yanbian University, Yanji 133002, People’s Republic of China
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29
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Volpi R, Nassau R, Nørby MS, Linares M. Theoretical Study of the Charge-Transfer State Separation within Marcus Theory: The C60-Anthracene Case Study. ACS APPLIED MATERIALS & INTERFACES 2016; 8:24722-24736. [PMID: 27561228 DOI: 10.1021/acsami.6b06645] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We study, within Marcus theory, the possibility of the charge-transfer (CT) state splitting at organic interfaces and a subsequent transport of the free charge carriers to the electrodes. As a case study we analyze model anthracene-C60 interfaces. Kinetic Monte Carlo (KMC) simulations on the cold CT state were performed at a range of applied electric fields, and with the fields applied at a range of angles to the interface to simulate the action of the electric field in a bulk heterojunction (BHJ) interface. The results show that the inclusion of polarization in our model increases CT state dissociation and charge collection. The effect of the electric field on CT state splitting and free charge carrier conduction is analyzed in detail with and without polarization. Also, depending on the relative orientation of the anthracene and C60 molecules at the interface, CT state splitting shows different behavior with respect to both applied field strength and applied field angle. The importance of the hot CT in helping the charge carrier dissociation is also analyzed in our scheme.
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Affiliation(s)
- Riccardo Volpi
- Department of Physics, Chemistry and Biology (IFM), Linköping University , SE-581 83 Linköping, Sweden
- Swedish e-Science Research Centre (SeRC), Linköping University , SE-581 83 Linköping, Sweden
| | - Racine Nassau
- Department of Physics, Chemistry and Biology (IFM), Linköping University , SE-581 83 Linköping, Sweden
| | - Morten Steen Nørby
- Department of Physics, Chemistry and Biology (IFM), Linköping University , SE-581 83 Linköping, Sweden
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark , DK-5230 Odense M, Denmark
| | - Mathieu Linares
- Department of Physics, Chemistry and Biology (IFM), Linköping University , SE-581 83 Linköping, Sweden
- Swedish e-Science Research Centre (SeRC), Linköping University , SE-581 83 Linköping, Sweden
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30
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Roscioni OM, Zannoni C. Molecular Dynamics Simulations and their Application to Thin-film Devices. UNCONVENTIONAL THIN FILM PHOTOVOLTAICS 2016. [DOI: 10.1039/9781782624066-00391] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The performance of devices based on organic semiconductors strongly depends on the molecular organisation in thin films. Due to the intrinsic complexity of these systems, a combination of theoretical modelling and experimental techniques is often the key to achieve a full understanding of their inner working. Here, we introduce the modelling of organic semiconductors by means of molecular dynamics simulations. We describe the basic theoretical framework of the technique and review the most popular class of force fields used to model organic materials, paying particular attention to the peculiarities of confined systems like nano-thick films. Representative studies of the organisation of organic functional materials in thin film phases are also reviewed.
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Affiliation(s)
- Otello Maria Roscioni
- Dipartimento di Chimica Industriale “Toso Montanari”, Università di Bologna viale Risorgimento 4 40136 Bologna Italy
| | - Claudio Zannoni
- Dipartimento di Chimica Industriale “Toso Montanari”, Università di Bologna viale Risorgimento 4 40136 Bologna Italy
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31
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Shen XX, Han GC, Yi YP. Multiscale description of molecular packing and electronic processes in small-molecule organic solar cells. CHINESE CHEM LETT 2016. [DOI: 10.1016/j.cclet.2016.05.030] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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32
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Wu B, Zhao Y, Nan H, Yang Z, Zhang Y, Zhao H, He D, Jiang Z, Liu X, Li Y, Shi Y, Ni Z, Wang J, Xu JB, Wang X. Precise, Self-Limited Epitaxy of Ultrathin Organic Semiconductors and Heterojunctions Tailored by van der Waals Interactions. NANO LETTERS 2016; 16:3754-9. [PMID: 27183049 DOI: 10.1021/acs.nanolett.6b01108] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Precise assembly of semiconductor heterojunctions is the key to realize many optoelectronic devices. By exploiting the strong and tunable van der Waals (vdW) forces between graphene and organic small molecules, we demonstrate layer-by-layer epitaxy of ultrathin organic semiconductors and heterostructures with unprecedented precision with well-defined number of layers and self-limited characteristics. We further demonstrate organic p-n heterojunctions with molecularly flat interface, which exhibit excellent rectifying behavior and photovoltaic responses. The self-limited organic molecular beam epitaxy (SLOMBE) is generically applicable for many layered small-molecule semiconductors and may lead to advanced organic optoelectronic devices beyond bulk heterojunctions.
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Affiliation(s)
- Bing Wu
- National Laboratory of Solid State Microstructures, School of Electronic Science and Engineering, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University , Nanjing 210093, China
| | - Yinghe Zhao
- Department of Physics, Southeast University , Nanjing 211189, People's Republic of China
| | - Haiyan Nan
- Department of Physics, Southeast University , Nanjing 211189, People's Republic of China
| | - Ziyi Yang
- National Laboratory of Solid State Microstructures, School of Electronic Science and Engineering, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University , Nanjing 210093, China
| | - Yuhan Zhang
- National Laboratory of Solid State Microstructures, School of Electronic Science and Engineering, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University , Nanjing 210093, China
| | - Huijuan Zhao
- National Laboratory of Solid State Microstructures, School of Electronic Science and Engineering, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University , Nanjing 210093, China
| | - Daowei He
- National Laboratory of Solid State Microstructures, School of Electronic Science and Engineering, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University , Nanjing 210093, China
| | - Zonglin Jiang
- National Laboratory of Solid State Microstructures, School of Electronic Science and Engineering, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University , Nanjing 210093, China
| | - Xiaolong Liu
- National Laboratory of Solid State Microstructures, School of Electronic Science and Engineering, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University , Nanjing 210093, China
| | - Yun Li
- National Laboratory of Solid State Microstructures, School of Electronic Science and Engineering, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University , Nanjing 210093, China
| | - Yi Shi
- National Laboratory of Solid State Microstructures, School of Electronic Science and Engineering, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University , Nanjing 210093, China
| | - Zhenhua Ni
- Department of Physics, Southeast University , Nanjing 211189, People's Republic of China
| | - Jinlan Wang
- Department of Physics, Southeast University , Nanjing 211189, People's Republic of China
- Synergetic Innovation Center for Quantum Effects and Applications (SICQEA), Hunan Normal University , Changsha 410081, China
| | - Jian-Bin Xu
- Department of Electronic Engineering and Materials Science and Technology Research Center, The Chinese University of Hong Kong , Hong Kong SAR, People's Republic of China
| | - Xinran Wang
- National Laboratory of Solid State Microstructures, School of Electronic Science and Engineering, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University , Nanjing 210093, China
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Casalegno M, Moret M, Resel R, Raos G. Surface Reconstructions in Organic Crystals: Simulations of the Effect of Temperature and Defectivity on Bulk and (001) Surfaces of 2,2':6',2″-Ternaphthalene. CRYSTAL GROWTH & DESIGN 2016; 16:412-422. [PMID: 26834509 PMCID: PMC4720359 DOI: 10.1021/acs.cgd.5b01405] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Revised: 11/17/2015] [Indexed: 06/05/2023]
Abstract
2,2':6',2″-Ternaphthalene (NNN) is a novel, blue-emitting material, suitable for preparation of organic light-emitting diodes. Its crystal structure has been solved recently, but its thermal behavior and surface properties have not yet been explored, partly due to the difficulty in obtaining high quality crystals. In the present study we use classical molecular dynamics to investigate the thermal behavior of bulk and (001) surfaces of NNN. Our bulk simulations indicate the occurrence of a phase transition at about 600 K. The transition is facilitated by the presence of a free (001) surface, since a reconstruction leading to a very similar structure occurs around 550 K in our surface models. This holds for both ideal and defective surface models, containing a small number of vacancies (one or two missing molecules in the outermost layer). In all cases, the process is triggered by thermal motion and involves the reorientation of the molecules with respect to the (001) plane. Both the bulk and surface phases share the monoclinic space group P21/a with a herringbone disposition of molecules. These findings and their implications for the use of NNN in organic electronics are discussed.
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Affiliation(s)
- Mosè Casalegno
- Dipartimento di Chimica, Materiali e Ingegneria Chimica "G. Natta", Politecnico di Milano , Via L. Mancinelli 7, 20131 Milano, Italy
| | - Massimo Moret
- Dipartimento di Scienza dei Materiali, Università degli Studi di Milano-Bicocca , Via R. Cozzi 55, 20125 Milano, Italy
| | - Roland Resel
- Institut für Festkörperphysik, Technische Universität Graz , 60101 Graz, Austria
| | - Guido Raos
- Dipartimento di Chimica, Materiali e Ingegneria Chimica "G. Natta", Politecnico di Milano , Via L. Mancinelli 7, 20131 Milano, Italy
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Beltrán J, Flores F, Ortega J. The role of charge transfer in the energy level alignment at the pentacene/C60 interface. Phys Chem Chem Phys 2014; 16:4268-74. [PMID: 24452709 DOI: 10.1039/c3cp55004d] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Understanding the mechanism of energy level alignment at organic-organic interfaces is a crucial line of research to optimize applications in organic electronics. We address this problem for the C60-pentacene interface by performing local-orbital Density Functional Theory (DFT) calculations, including the effect of the charging energies on the energy gap of both organic materials. The results are analyzed within the induced density of interface states (IDIS) model. We find that the induced interface potential is in the range of 0.06-0.10 eV, in good agreement with the experimental evidence, and that such potential is mainly induced by the small, but non-negligible, charge transfer between the two compounds and the multipolar contribution associated with pentacene. We also suggest that an appropriate external intercompound potential could create an insulator-metal transition at the interface.
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Affiliation(s)
- J Beltrán
- Depto. de Física Teórica de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, 28049-Madrid, Spain.
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35
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Theoretical description of the geometric and electronic structures of organic-organic interfaces in organic solar cells: a brief review. Sci China Chem 2014. [DOI: 10.1007/s11426-014-5184-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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36
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Akimov AV, Prezhdo OV. Nonadiabatic Dynamics of Charge Transfer and Singlet Fission at the Pentacene/C60 Interface. J Am Chem Soc 2014; 136:1599-608. [DOI: 10.1021/ja411800n] [Citation(s) in RCA: 119] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Alexey V. Akimov
- Department
of Chemistry, University of Rochester, Rochester, New York 14627, United States
- Department
of Chemistry, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - Oleg V. Prezhdo
- Department
of Chemistry, University of Rochester, Rochester, New York 14627, United States
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Breuer T, Witte G. Diffusion-controlled growth of molecular heterostructures: fabrication of two-, one-, and zero-dimensional C(60) nanostructures on pentacene substrates. ACS APPLIED MATERIALS & INTERFACES 2013; 5:9740-9745. [PMID: 24004066 DOI: 10.1021/am402868s] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
A variety of low dimensional C60 structures has been grown on supporting pentacene multilayers. By choice of substrate temperature during growth the effective diffusion length of evaporated fullerenes and their nucleation at terraces or step edges can be precisely controlled. AFM and SEM measurements show that this enables the fabrication of either 2D adlayers or solely 1D chains decorating substrate steps, while at elevated growth temperature continuous wetting of step edges is prohibited and instead the formation of separated C60 clusters pinned at the pentacene step edges occurs. Remarkably, all structures remain thermally stable at room temperature once they are formed. In addition the various fullerene structures have been overgrown by an additional pentacene capping layer. Utilizing the different probe depth of XRD and NEXAFS, we found that no contiguous pentacene film is formed on the 2D C60 structure, whereas an encapsulation of the 1D and 0D structures with uniformly upright oriented pentacene is achieved, hence allowing the fabrication of low dimensional buried organic heterostructures.
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Affiliation(s)
- Tobias Breuer
- Molekulare Festkörperphysik, Philipps-Universität Marburg , D-35032 Marburg, Germany
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38
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Wilson MWB, Rao A, Ehrler B, Friend RH. Singlet exciton fission in polycrystalline pentacene: from photophysics toward devices. Acc Chem Res 2013; 46:1330-8. [PMID: 23656886 DOI: 10.1021/ar300345h] [Citation(s) in RCA: 136] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Singlet exciton fission is the process in conjugated organic molecules bywhich a photogenerated singlet exciton couples to a nearby chromophore in the ground state, creating a pair of triplet excitons. Researchers first reported this phenomenon in the 1960s, an event that sparked further studies in the following decade. These investigations used fluorescence spectroscopy to establish that exciton fission occurred in single crystals of several acenes. However, research interest has been recently rekindled by the possibility that singlet fission could be used as a carrier multiplication technique to enhance the efficiency of photovoltaic cells. The most successful architecture to-date involves sensitizing a red-absorbing photoactive layer with a blue-absorbing material that undergoes fission, thereby generating additional photocurrent from higher-energy photons. The quest for improved solar cells has spurred a drive to better understand the fission process, which has received timely aid from modern techniques for time-resolved spectroscopy, quantum chemistry, and small-molecule device fabrication. However, the consensus interpretation of the initial studies using ultrafast transient absorption spectroscopy was that exciton fission was suppressed in polycrystalline thin films of pentacene, a material that would be otherwise expected to be an ideal model system, as well as a viable candidate for fission-sensitized photovoltaic devices. In this Account, we review the results of our recent transient absorption and device-based studies of polycrystalline pentacene. We address the controversy surrounding the assignment of spectroscopic features in transient absorption data, and illustrate how a consistent interpretation is possible. This work underpins our conclusion that singlet fission in pentacene is extraordinarily rapid (∼80 fs) and is thus the dominant decay channel for the photoexcited singlet exciton. Further, we discuss our demonstration that triplet excitons generated via singlet fission in pentacene can be dissociated at an interface with a suitable electron acceptor, such as fullerenes and infrared-absorbing inorganic semiconducting quantum dots. We highlight our recent reports of a pentacene/PbSe hybrid solar cell with a power conversion efficiency of 4.7% and of a pentacene/PbSe/amorphous silicon photovoltaic device. Although substantive challenges remain, both to better our understanding of the mechanism of singlet exciton fission and to optimize device performance, this realization of a solar cell where photocurrent is simultaneously contributed from a blue-absorbing fission-capable material and an infrared-absorbing conventional cell is an important step towards a dual-bandgap, single-junction, fission-enhanced photovoltaic device, which could one day surpass the Shockley-Queisser limit.
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Affiliation(s)
- Mark W. B. Wilson
- Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE, U.K
| | - Akshay Rao
- Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE, U.K
| | - Bruno Ehrler
- Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE, U.K
| | - Richard H. Friend
- Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE, U.K
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40
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Cornil J, Verlaak S, Martinelli N, Mityashin A, Olivier Y, Van Regemorter T, D’Avino G, Muccioli L, Zannoni C, Castet F, Beljonne D, Heremans P. Exploring the energy landscape of the charge transport levels in organic semiconductors at the molecular scale. Acc Chem Res 2013; 46:434-43. [PMID: 23140088 DOI: 10.1021/ar300198p] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The extraordinary semiconducting properties of conjugated organic materials continue to attract attention across disciplines including materials science, engineering, chemistry, and physics, particularly with application to organic electronics. Such materials are used as active components in light-emitting diodes, field-effect transistors, or photovoltaic cells, as a substitute for (mostly Si-based) inorganic semiconducting materials. Many strategies developed for inorganic semiconductor device building (doping, p-n junctions, etc.) have been attempted, often successfully, with organics, even though the key electronic and photophysical properties of organic thin films are fundamentally different from those of their bulk inorganic counterparts. In particular, organic materials consist of individual units (molecules or conjugated segments) that are coupled by weak intermolecular forces. The flexibility of organic synthesis has allowed the development of more efficient opto-electronic devices including impressive improvements in quantum yields for charge generation in organic solar cells and in light emission in electroluminescent displays. Nonetheless, a number of fundamental questions regarding the working principles of these devices remain that preclude their full optimization. For example, the role of intermolecular interactions in driving the geometric and electronic structures of solid-state conjugated materials, though ubiquitous in organic electronic devices, has long been overlooked, especially when it comes to these interfaces with other (in)organic materials or metals. Because they are soft and in most cases disordered, conjugated organic materials support localized electrons or holes associated with local geometric distortions, also known as polarons, as primary charge carriers. The spatial localization of excess charges in organics together with low dielectric constant (ε) entails very large electrostatic effects. It is therefore not obvious how these strongly interacting electron-hole pairs can potentially escape from their Coulomb well, a process that is at the heart of photoconversion or molecular doping. Yet they do, with near-quantitative yield in some cases. Limited screening by the low dielectric medium in organic materials leads to subtle static and dynamic electronic polarization effects that strongly impact the energy landscape for charges, which offers a rationale for this apparent inconsistency. In this Account, we use different theoretical approaches to predict the energy landscape of charge carriers at the molecular level and review a few case studies highlighting the role of electrostatic interactions in conjugated organic molecules. We describe the pros and cons of different theoretical approaches that provide access to the energy landscape defining the motion of charge carriers. We illustrate the applications of these approaches through selected examples involving OFETs, OLEDs, and solar cells. The three selected examples collectively show that energetic disorder governs device performances and highlights the relevance of theoretical tools to probe energy landscapes in molecular assemblies.
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Affiliation(s)
- J. Cornil
- Laboratory for Chemistry of Novel Materials, University of Mons, Place du Parc 20, B-7000 Mons, Belgium
| | - S. Verlaak
- imec, Kapeldreef 75, B-3001, Leuven, Belgium
| | - N. Martinelli
- Laboratory for Chemistry of Novel Materials, University of Mons, Place du Parc 20, B-7000 Mons, Belgium
| | - A. Mityashin
- imec, Kapeldreef 75, B-3001, Leuven, Belgium
- ESAT, Katholieke Universiteit Leuven, Kasteelpark Arenberg 10, B-3001 Leuven, Belgium
| | - Y. Olivier
- Laboratory for Chemistry of Novel Materials, University of Mons, Place du Parc 20, B-7000 Mons, Belgium
| | - T. Van Regemorter
- Laboratory for Chemistry of Novel Materials, University of Mons, Place du Parc 20, B-7000 Mons, Belgium
| | - G. D’Avino
- Dipartimento di Chimica Fisica e Inorganica and INSTM, Università di Bologna, IT-40136 Bologna, Italy
| | - L. Muccioli
- Dipartimento di Chimica Fisica e Inorganica and INSTM, Università di Bologna, IT-40136 Bologna, Italy
| | - C. Zannoni
- Dipartimento di Chimica Fisica e Inorganica and INSTM, Università di Bologna, IT-40136 Bologna, Italy
| | - F. Castet
- Institut des Sciences Moléculaires, UMR CNRS 5255, Université de Bordeaux, Cours de la Libération 351, FR-33405 Talence, France
| | - D. Beljonne
- Laboratory for Chemistry of Novel Materials, University of Mons, Place du Parc 20, B-7000 Mons, Belgium
| | - P. Heremans
- imec, Kapeldreef 75, B-3001, Leuven, Belgium
- ESAT, Katholieke Universiteit Leuven, Kasteelpark Arenberg 10, B-3001 Leuven, Belgium
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41
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Muccioli L, D’Avino G, Berardi R, Orlandi S, Pizzirusso A, Ricci M, Roscioni OM, Zannoni C. Supramolecular Organization of Functional Organic Materials in the Bulk and at Organic/Organic Interfaces: A Modeling and Computer Simulation Approach. Top Curr Chem (Cham) 2013; 352:39-101. [DOI: 10.1007/128_2013_470] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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42
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Chen S, Ma J. Substituent effects on packing entropy and film morphologies in the nucleation of functionalized pentacenes on SiO2 substrate: Molecular dynamics simulations. J Chem Phys 2012; 137:074708. [DOI: 10.1063/1.4745899] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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43
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Feng H, Becker KE, Zhou J, Fichthorn KA. Molecular thin films on solid surfaces: mechanisms of melting. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:7382-7392. [PMID: 22524414 DOI: 10.1021/la300826p] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We use molecular dynamics simulations to study the melting of pentane and hexane monolayers adsorbed on the basal plane of graphite. For both of these systems, the temperature-dependent structures and the melting temperatures agree well with experiment. A detailed analysis reveals that a mechanism involving the promotion of molecules to the second layer underlies melting in these systems. In the second-layer promotion mechanism, a small fraction of molecules transition into the second layer around the melting temperature, leaving vacant space in the first layer to facilitate disordering. The second-layer promotion mechanism arises because of the weaker molecule-surface interaction in our study than that in previous studies. The weaker molecule-surface interaction is consistent with experimental temperature-programmed desorption studies.
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Affiliation(s)
- Haijun Feng
- Department of Chemical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
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44
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Mou W, Ohmura S, Hattori S, Nomura KI, Shimojo F, Nakano A. Enhanced charge transfer by phenyl groups at a rubrene/C60 interface. J Chem Phys 2012; 136:184705. [PMID: 22583307 DOI: 10.1063/1.4712616] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Exciton dynamics at an interface between an electron donor, rubrene, and a C(60) acceptor is studied by nonadiabatic quantum molecular dynamics simulation. Simulation results reveal an essential role of the phenyl groups in rubrene in increasing the charge-transfer rate by an order-of-magnitude. The atomistic mechanism of the enhanced charge transfer is found to be the amplification of aromatic breathing modes by the phenyl groups, which causes large fluctuations of electronic excitation energies. These findings provide insight into molecular structure design for efficient solar cells, while explaining recent experimental observations.
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Affiliation(s)
- Weiwei Mou
- Collaboratory for Advanced Computing and Simulations, Department of Physics & Astronomy, University of Southern California, Los Angeles, California 90089-0242, USA
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45
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Hopp SF, Heuer A. Anisotropic behavior of organic molecules on prepatterned surfaces. J Chem Phys 2012; 136:154106. [PMID: 22519314 DOI: 10.1063/1.3692289] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The nucleation of organic molecules on surfaces, prepatterned with stripes, is investigated with emphasis on anisotropy effects. Representing the molecules as ellipsoids, the related particle-particle interaction is modeled by means of a generalized Gay-Berne potential for similar biaxial particles. The orientation behavior of these ellipsoidal molecules induced by the stripe pattern is studied for the first monolayer by performing kinetic Monte Carlo simulations. It is shown how the properties of the particle alignment depend on energy scales, temperature, and flux. Based on the fact the particles strictly arrange in rows, it is furthermore instructive to analyze the orientation behavior within the different rows. Finally, the transfer of orientation from a preset row of molecules with fixed orientation to other nucleating particles is examined.
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Affiliation(s)
- Stefan Frieder Hopp
- Westfälische Wilhelms-Universität Münster, Institut für Physikalische Chemie, Corrensstr. 28/30, 48149 Münster, Germany
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Lu Z, Zhan C, Yu X, He W, Jia H, Chen L, Tang A, Huang J, Yao J. Large-scale, ultra-dense and vertically standing zinc phthalocyanine π–π stacks as a hole-transporting layer on an ITO electrode. ACTA ACUST UNITED AC 2012. [DOI: 10.1039/c2jm35342c] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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47
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Baumeier B, May F, Lennartz C, Andrienko D. Challenges for in silico design of organic semiconductors. ACTA ACUST UNITED AC 2012. [DOI: 10.1039/c2jm30182b] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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