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Stäter S, Woering EF, Lombeck F, Sommer M, Hildner R. Hexylation Stabilises Twisted Backbone Configurations in the Prototypical Low-Bandgap Copolymer PCDTBT. Chemphyschem 2024; 25:e202300971. [PMID: 38372667 DOI: 10.1002/cphc.202300971] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Revised: 02/19/2024] [Accepted: 02/19/2024] [Indexed: 02/20/2024]
Abstract
Conjugated donor-acceptor copolymers hold great potential as materials for high-performance organic photovoltaics, organic transistors and organic thermoelectric devices. Their low optical bandgap is achieved by alternation of donor and acceptor moieties along the polymer chain, leading to a pronounced charge-transfer character of electronic excitations. However, the influence of appended side chains and of chemical defects of the backbone on their photophysical and conformational properties remains largely unexplored on the level of individual chains. Here, we employ room temperature single-molecule photoluminescence spectroscopy on four compounds based on the prototypical copolymer PCDTBT with systematically changed chemical structure. Our results show that an increasing density of statistically added hexyl chains to the TBT comonomer distorts the molecular conformation, likely through the increase of average dihedral angles along the backbone. We find that, although the conformation becomes more twisted with high hexyl density, the side chains appear to stabilize the backbone in this twisted conformation. In addition, we demonstrate that homocoupling defects along the backbone barely influence the PL spectra of single chains, and thus intra-chain electronic properties.
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Affiliation(s)
- Sebastian Stäter
- University of Groningen, Zernike Institute for Advanced Materials, 9747AG, Groningen, Netherlands
| | - Erik F Woering
- University of Groningen, Zernike Institute for Advanced Materials, 9747AG, Groningen, Netherlands
| | - Florian Lombeck
- Makromolekulare Chemie, Stefan-Meier-Str. 31, Universität Freiburg, 79104, Freiburg, Germany
- Optoelectronics Group, Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Michael Sommer
- TU Chemnitz, Institute for Chemistry, Str. der Nationen 62, 09111, Chemnitz, Germany
| | - Richard Hildner
- University of Groningen, Zernike Institute for Advanced Materials, 9747AG, Groningen, Netherlands
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Ghosh R, Paesani F. Connecting the dots for fundamental understanding of structure-photophysics-property relationships of COFs, MOFs, and perovskites using a Multiparticle Holstein Formalism. Chem Sci 2023; 14:1040-1064. [PMID: 36756323 PMCID: PMC9891456 DOI: 10.1039/d2sc03793a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Accepted: 11/09/2022] [Indexed: 11/17/2022] Open
Abstract
Photoactive organic and hybrid organic-inorganic materials such as conjugated polymers, covalent organic frameworks (COFs), metal-organic frameworks (MOFs), and layered perovskites, display intriguing photophysical signatures upon interaction with light. Elucidating structure-photophysics-property relationships across a broad range of functional materials is nontrivial and requires our fundamental understanding of the intricate interplay among excitons (electron-hole pair), polarons (charges), bipolarons, phonons (vibrations), inter-layer stacking interactions, and different forms of structural and conformational defects. In parallel with electronic structure modeling and data-driven science that are actively pursued to successfully accelerate materials discovery, an accurate, computationally inexpensive, and physically-motivated theoretical model, which consistently makes quantitative connections with conceptually complicated experimental observations, is equally important. Within this context, the first part of this perspective highlights a unified theoretical framework in which the electronic coupling as well as the local coupling between the electronic and nuclear degrees of freedom can be efficiently described for a broad range of quasiparticles with similarly structured Holstein-style vibronic Hamiltonians. The second part of this perspective discusses excitonic and polaronic photophysical signatures in polymers, COFs, MOFs, and perovskites, and attempts to bridge the gap between different research fields using a common theoretical construct - the Multiparticle Holstein Formalism. We envision that the synergistic integration of state-of-the-art computational approaches with the Multiparticle Holstein Formalism will help identify and establish new, transformative design strategies that will guide the synthesis and characterization of next-generation energy materials optimized for a broad range of optoelectronic, spintronic, and photonic applications.
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Affiliation(s)
- Raja Ghosh
- Department of Chemistry and Biochemistry, University of California La Jolla San Diego California 92093 USA
| | - Francesco Paesani
- Department of Chemistry and Biochemistry, University of California La Jolla San Diego California 92093 USA
- San Diego Supercomputer Center, University of California La Jolla San Diego California 92093 USA
- Materials Science and Engineering, University of California La Jolla San Diego California 92093 USA
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Abstract
ConspectusExcitons and polarons play a central role in the electronic and optical properties of organic semiconducting polymers and molecular aggregates and are of fundamental importance in understanding the operation of organic optoelectronic devices such as solar cells and light-emitting diodes. For many conjugated organic molecules and polymers, the creation of neutral electronic excitations or ionic radicals is associated with significant nuclear relaxation, the bulk of which occurs along the vinyl-stretching mode or the aromatic-quinoidal stretching mode when conjugated rings are present. Within a polymer chain or molecular aggregate, nuclear relaxation competes with energy- and charge-transfer, mediated by electronic interactions between the constituent units (repeat units for polymers and individual chromophores for a molecular aggregate); for neutral electronic excitations, such inter-unit interactions lead to extended excited states or excitons, while for positive (or negative) charges, interactions lead to delocalized hole (or electron) polarons. The electronic coupling as well as the local coupling between electronic and nuclear degrees of freedom in both excitons and polarons can be described with a Holstein Hamiltonian. However, although excitons and polarons derive from similarly structured Hamiltonians, their optical signatures are quite distinct, largely due to differing ground states and optical selection rules.In this Account, we explore the similarities and differences in the spectral response of excitons and polarons in organic polymers and molecular aggregates. We limit our analysis to the subspace of excitons and hole polarons containing at most one excitation; hence we omit the influence of bipolarons, biexcitons, and higher multiparticle excitations. Using a generic linear array of coupled units as a model host for both excitons and polarons, we compare and contrast the optical responses of both quasiparticles, with a particular emphasis on the spatial coherence length, the length over which an exciton or polaron possesses wave-like properties important for more efficient transport. For excitons, the UV-vis absorption spectrum is generally represented by a distorted vibronic progression with H-like or J-like signatures depending on the sign of the electronic coupling, Jex. The spectrum broadens with increasing site disorder, with the spectral area preserved due to an oscillator strength sum rule. For (hole) polarons, the generally stronger electronic coupling results in a mid-IR spectrum consisting of a narrow, low-energy peak (A) with energy near a vibrational quantum of the vinyl stretching mode, and a broader, higher-energy feature (B). In contrast to the UV-vis spectrum, the mid-IR spectrum is invariant to the sign of the electronic coupling, th, and completely resistant to long-range disorder, where it remains entirely homogeneously broadened. Even in the presence of short-range disorder, the width of peak A remains surprisingly narrow as long as |th| remains sufficiently large, a property that can be understood in terms of Herzberg-Teller coupling. Unlike for excitons, for polarons, the absorption spectral area decreases with increasing short-range disorder σ (i.e., there is no oscillator sum rule) reflective of a decreasing polaron coherence length. The intensity of the low-energy peak A in relation to B is an important signature of polaron coherence. By contrast, for excitons, the absorption spectrum contains no unambiguous signs of exciton coherence. One must instead resort to the shape of the steady-state photoluminescence spectrum. The Holstein-based model has been highly successful in accounting for the spectral properties of molecular aggregates as well as conjugated polymers like poly(3-hexylthiophene) (P3HT) in the mid-IR and UV-vis spectral regions.
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Affiliation(s)
- Raja Ghosh
- Department of Chemistry Temple University, Philadelphia, Pennsylvania 19122, United States
| | - Frank C. Spano
- Department of Chemistry Temple University, Philadelphia, Pennsylvania 19122, United States
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Suresh SM, Duda E, Hall D, Yao Z, Bagnich S, Slawin AMZ, Bässler H, Beljonne D, Buck M, Olivier Y, Köhler A, Zysman-Colman E. A Deep Blue B,N-Doped Heptacene Emitter That Shows Both Thermally Activated Delayed Fluorescence and Delayed Fluorescence by Triplet–Triplet Annihilation. J Am Chem Soc 2020; 142:6588-6599. [DOI: 10.1021/jacs.9b13704] [Citation(s) in RCA: 106] [Impact Index Per Article: 26.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Subeesh Madayanad Suresh
- Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St. Andrews, St. Andrews, U.K. KY16 9ST
| | - Eimantas Duda
- Soft Matter Optoelectronics, University of Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany
| | - David Hall
- Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St. Andrews, St. Andrews, U.K. KY16 9ST
- Laboratory for Chemistry of Novel Materials, University of Mons, 7000 Mons, Belgium
| | - Zhen Yao
- Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St. Andrews, St. Andrews, U.K. KY16 9ST
| | - Sergey Bagnich
- Soft Matter Optoelectronics, University of Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany
| | - Alexandra M. Z. Slawin
- Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St. Andrews, St. Andrews, U.K. KY16 9ST
| | - Heinz Bässler
- BIMF, University of Bayreuth, 95447 Bayreuth, Germany
| | - David Beljonne
- Laboratory for Chemistry of Novel Materials, University of Mons, 7000 Mons, Belgium
| | - Manfred Buck
- Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St. Andrews, St. Andrews, U.K. KY16 9ST
| | - Yoann Olivier
- Laboratory for Chemistry of Novel Materials, University of Mons, 7000 Mons, Belgium
- Unité de Chimie Physique Théorique et Structurale & Laboratoire de Physique du Solide, Namur Institute of Structured Matter, Université de Namur, Rue de Bruxelles, 61, 5000 Namur, Belgium
| | - Anna Köhler
- Soft Matter Optoelectronics, University of Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany
| | - Eli Zysman-Colman
- Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St. Andrews, St. Andrews, U.K. KY16 9ST
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Fu Y, Zhai T. Distributed feedback organic lasing in photonic crystals. FRONTIERS OF OPTOELECTRONICS 2020; 13:18-34. [PMID: 36641584 PMCID: PMC9733769 DOI: 10.1007/s12200-019-0942-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Accepted: 08/11/2019] [Indexed: 05/14/2023]
Abstract
Considerable research efforts have been devoted to the investigation of distributed feedback (DFB) organic lasing in photonic crystals in recent decades. It is still a big challenge to realize DFB lasing in complex photonic crystals. This review discusses the recent progress on the DFB organic laser based on one-, two-, and three-dimensional photonic crystals. The photophysics of gain materials and the fabrication of laser cavities are also introduced. At last, future development trends of the lasers are prospected.
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Affiliation(s)
- Yulan Fu
- Institute of Information Photonics Technology, College of Applied Sciences, Beijing University of Technology, Beijing, 100124, China
| | - Tianrui Zhai
- Institute of Information Photonics Technology, College of Applied Sciences, Beijing University of Technology, Beijing, 100124, China.
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Milward JD, Marcus M, Köhler A, Barford W. Extracting structural information from MEH-PPV optical spectra. J Chem Phys 2018; 149:044903. [PMID: 30068188 DOI: 10.1063/1.5041938] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The Frenkel-Holstein model in the Born-Oppenheimer regime is used to interpret temperature-dependent photoluminescence spectra of solutions made with the poly(p-phenylene vinylene) derivative MEH-PPV. Using our recently developed structural optimization method and assuming only intrachain electronic coupling, we predict the structure of emissive MEH-PPV chromophores in terms of a mean torsional angle ϕ0 and its static fluctuations σϕ, assuming no cis-trans defects. This allows us to fully account for the observed changes in spectra, and the chromophore structures obtained are consistent with the known phase transition at 180 K between a "red" and "blue" phase.
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Affiliation(s)
- Jonathan D Milward
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, Oxford OX1 3QZ, United Kingdom
| | - Max Marcus
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, Oxford OX1 3QZ, United Kingdom
| | - Anna Köhler
- Experimental Physics II, University of Bayreuth, 95447 Bayreuth, Germany and Bayreuth Institute of Macromolecular Research (BIMF), University of Bayreuth, 95447 Bayreuth, Germany
| | - William Barford
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, Oxford OX1 3QZ, United Kingdom
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