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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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2
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Yuan X, Yang K, Grazon C, Wang C, Vallan L, Isasa JD, Resende PM, Li F, Brochon C, Remita H, Hadziioannou G, Cloutet E, Li J. Tuning the Aggregates of Thiophene-based Trimers by Methyl Side-chain Engineering for Photocatalytic Hydrogen Evolution. Angew Chem Int Ed Engl 2024; 63:e202315333. [PMID: 37994609 DOI: 10.1002/anie.202315333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Revised: 11/08/2023] [Accepted: 11/20/2023] [Indexed: 11/24/2023]
Abstract
Organic π-conjugated semiconductors (OCSs) have recently emerged as a promising alternative to traditional inorganic materials for photocatalysis. However, the aggregation of OCSs in photocatalytic aqueous solution caused by self-assembly, which closely relates to the photocatalytic activity, has not yet been studied. Here, the relationship between the aggregation of 4,7-Bis(thiophen-2-yl) benzothiadiazole (TBT) and the photocatalytic activity was systematically investigated by introducing and varying the position of methyl side chains on the two peripheral thiophene units. Experimental and theoretical results indicated that the introduction of -CH3 group at the 3-position of TBT resulted in the smallest size and best crystallinity of aggregates compared to that of TBT, 4- and 5-positions. As a result, TBT-3 exhibited an excellent photocatalytic activity towards H2 evolution, ascribed to the shorten charge carrier transport distance and solid long-range order. These results suggest the important role of aggregation behavior of OCSs for efficient photocatalysis.
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Affiliation(s)
- Xiaojiao Yuan
- Université de Bordeaux, CNRS, Bordeaux INP, LCPO, UMR5629, Allée Geoffroy Saint Hilaire, Bâtiment B8, 33607, Pessac, France
| | - Kunran Yang
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695-7905, USA
| | - Chloé Grazon
- Univ. Bordeaux, CNRS, Bordeaux INP, ISM, UMR 5255, 33400, Talence, France
| | - Cong Wang
- Institut de Chimie Physique, UMR 8000 CNRS, Université Paris-Saclay, 310 Rue Michel Magat, 91400, Orsay, France
| | - Lorenzo Vallan
- Université de Bordeaux, CNRS, Bordeaux INP, LCPO, UMR5629, Allée Geoffroy Saint Hilaire, Bâtiment B8, 33607, Pessac, France
| | - Jean-David Isasa
- Université de Bordeaux, CNRS, Bordeaux INP, LCPO, UMR5629, Allée Geoffroy Saint Hilaire, Bâtiment B8, 33607, Pessac, France
| | - Pedro M Resende
- Université de Bordeaux, CNRS, Bordeaux INP, LCPO, UMR5629, Allée Geoffroy Saint Hilaire, Bâtiment B8, 33607, Pessac, France
| | - Fanxing Li
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695-7905, USA
| | - Cyril Brochon
- Université de Bordeaux, CNRS, Bordeaux INP, LCPO, UMR5629, Allée Geoffroy Saint Hilaire, Bâtiment B8, 33607, Pessac, France
| | - Hynd Remita
- Institut de Chimie Physique, UMR 8000 CNRS, Université Paris-Saclay, 310 Rue Michel Magat, 91400, Orsay, France
| | - Georges Hadziioannou
- Université de Bordeaux, CNRS, Bordeaux INP, LCPO, UMR5629, Allée Geoffroy Saint Hilaire, Bâtiment B8, 33607, Pessac, France
| | - Eric Cloutet
- Université de Bordeaux, CNRS, Bordeaux INP, LCPO, UMR5629, Allée Geoffroy Saint Hilaire, Bâtiment B8, 33607, Pessac, France
| | - Jian Li
- Institut de Chimie Physique, UMR 8000 CNRS, Université Paris-Saclay, 310 Rue Michel Magat, 91400, Orsay, France
- Laboratory of Renewable Energy Science and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Switzerland
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Zhang X, Ivanov M, Wang Z, Bousquet MHE, Liu X, Wan Y, Zhao J, Barbon A, Escudero D, Jacquemin D, Fedin M. Confinement of the Triplet States in π‐Conjugated BODIPY Dimers Linked with Ethynylene or Butadiynylene Bridges: A Different View on the Effect of Symmetry. Angew Chem Int Ed Engl 2022; 61:e202210419. [PMID: 36216789 PMCID: PMC10092165 DOI: 10.1002/anie.202210419] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2022] [Indexed: 11/07/2022]
Abstract
Understanding the impact of the excited state wavefunction confinement is crucial for the engineering of the photophysical properties and applications of organic chromophores. In the present contribution, the localization of the triplet state wavefunctions of some symmetric ethyne/butadiyne bridged BODIPY dimers and asymmetric BODIPY derivatives presenting extended π-conjugation frameworks is studied with time-resolved electron paramagnetic resonance spectroscopy and time-dependent density functional theory computations. Based on the Zero Field Splitting D parameters, we conclude that the triplet state wavefunctions are highly localized on one BODIPY unit in the symmetric dimers, which is consistent with the ab initio modelling that finds delocalized triplet state destabilized by 12-14 kcal mol-1 as compared to its localized counterpart. The result provides a new insight into the study of triplet excited state confinement and the design of molecular wires or photosensitizers for photovoltaics and photocatalysis.
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Affiliation(s)
- Xue Zhang
- State Key Laboratory of Fine Chemicals Frontiers Science Center for Smart Materials School of Chemical Engineering Dalian University of Technology 2 Ling Gong Road Dalian 116024 P. R. China
| | - Mikhail Ivanov
- International Tomography Center SB RAS Institutskaya Str., 3A 630090 Novosibirsk Russia
- Novosibirsk State University Pirogova str. 2 630090 Novosibirsk Russia
| | - Zhijia Wang
- State Key Laboratory of Fine Chemicals Frontiers Science Center for Smart Materials School of Chemical Engineering Dalian University of Technology 2 Ling Gong Road Dalian 116024 P. R. China
| | | | - Xi Liu
- College of Chemistry Beijing Normal University Beijing 100875 P. R. China
| | - Yan Wan
- College of Chemistry Beijing Normal University Beijing 100875 P. R. China
| | - Jianzhang Zhao
- State Key Laboratory of Fine Chemicals Frontiers Science Center for Smart Materials School of Chemical Engineering Dalian University of Technology 2 Ling Gong Road Dalian 116024 P. R. China
| | - Antonio Barbon
- Dipartimento di Scienze Chimiche Università degli Studi di Padova 35131 Padova Italy
| | - Daniel Escudero
- Department of Chemistry KU Leuven Celestijnenlaan 200F 3001 Leuven Belgium
| | - Denis Jacquemin
- Nantes Université CNRS CEISAM UMR 6230 44300 Nantes France
- Institut Universitaire de France 75005 Paris France
| | - Matvey Fedin
- International Tomography Center SB RAS Institutskaya Str., 3A 630090 Novosibirsk Russia
- Novosibirsk State University Pirogova str. 2 630090 Novosibirsk Russia
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Mavrommati SA, Skourtis SS. Initial-state preparation effects in time-resolved electron paramagnetic resonance experiments. J Chem Phys 2020; 152:044304. [DOI: 10.1063/1.5127806] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
| | - Spiros S. Skourtis
- Department of Physics, University of Cyprus, P.O. Box 20537, Nicosia 1678, Cyprus
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Matt C, Stry K, Matsidik R, Sommer M, Biskup T. Two competing acceptors: Electronic structure of PNDITBT probed by time-resolved electron paramagnetic resonance spectroscopy. J Chem Phys 2019; 151:234901. [PMID: 31864273 DOI: 10.1063/1.5128469] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Balanced charge transport is particularly important for transistors. Hence, ambipolar organic semiconductors with comparable transport capabilities for both positive and negative charges are highly sought-after. Here, we report detailed insights into the electronic structure of PNDITBT, which is an alternating copolymer of naphthalene diimide (NDI), thiophene, benzothiodiazole (B), and thiophene (T) units, as gained by time-resolved electron paramagnetic resonance (TREPR) spectroscopy combined with quantum-chemical calculations. The results are compared to those obtained for PNDIT2 and PCDTBT, which are derivatives without B and NDI acceptor units, respectively. These two polymers show dominant n- and p-channel behavior in organic field-effect transistors. The TBT moiety clearly dominates the electronic structure of PNDITBT, although less so than in PCDTBT. Furthermore, the triplet exciton most probably delocalizes along the backbone, exhibits a highly homogeneous environment, and planarizes the polymer backbone. Obtaining the zero-field splitting tensors of these triplet states by means of quantum-chemical calculations reveals the triplet energy sublevel associated with the molecular axis parallel to the backbone to be preferentially populated, while the one perpendicular to the aromatic plane is not populated at all, consistent with the spin-density distribution. PNDITBT consisting of two acceptors (NDI and B) has a complex electronic structure, as evident from the two charge-transfer bands in its absorption spectrum. TREPR spectroscopy provides a detailed insight on a molecular level not available by and complementing other methods.
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Affiliation(s)
- Clemens Matt
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstraße 21, 79104 Freiburg, Germany
| | - Katja Stry
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstraße 21, 79104 Freiburg, Germany
| | - Rukiya Matsidik
- Institut für Makromolekulare Chemie, Albert-Ludwigs-Universität Freiburg, Stefan-Meier-Straße 31, 79104 Freiburg, Germany
| | - Michael Sommer
- Polymerchemie, Institut für Chemie, Technische Universität Chemnitz, Straße der Nationen 62, 09111 Chemnitz, Germany
| | - Till Biskup
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstraße 21, 79104 Freiburg, Germany
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Matt C, Lombeck F, Sommer M, Biskup T. Impact of Side Chains of Conjugated Polymers on Electronic Structure: A Case Study. Polymers (Basel) 2019; 11:E870. [PMID: 31086059 PMCID: PMC6572471 DOI: 10.3390/polym11050870] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Revised: 04/26/2019] [Accepted: 05/08/2019] [Indexed: 11/22/2022] Open
Abstract
Processing from solution is a crucial aspect of organic semiconductors, as it is at the heart of the promise of easy and inexpensive manufacturing of devices. Introducing alkyl side chains is an approach often used to increase solubility and enhance miscibility in blends. The influence of these side chains on the electronic structure, although highly important for a detailed understanding of the structure-function relationship of these materials, is still barely understood. Here, we use time-resolved electron paramagnetic resonance spectroscopy with its molecular resolution to investigate the role of alkyl side chains on the polymer PCDTBT and a series of its building blocks with increasing length. Comparing our results to the non-hexylated compounds allows us to distinguish four different factors determining exciton delocalization. Detailed quantum-chemical calculations (DFT) allows us to further interpret our spectroscopic data and to relate our findings to the molecular geometry. Alkylation generally leads to more localized excitons, most prominent only for the polymer. Furthermore, singlet excitons are more delocalized than the corresponding triplet excitons, despite the larger dihedral angles within the backbone found for the singlet-state geometries. Our results show TREPR spectroscopy of triplet excitons to be well suited for investigating crucial aspects of the structure-function relationship of conjugated polymers used as organic semiconductors on a molecular basis.
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Affiliation(s)
- Clemens Matt
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstraße 21, 79104 Freiburg, Germany.
| | - Florian Lombeck
- Institut für Makromolekulare Chemie, Albert-Ludwigs-Universität Freiburg, Stefan-Meier-Straße 31, 79104 Freiburg, Germany.
| | - Michael Sommer
- Institut für Makromolekulare Chemie, Albert-Ludwigs-Universität Freiburg, Stefan-Meier-Straße 31, 79104 Freiburg, Germany.
| | - Till Biskup
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstraße 21, 79104 Freiburg, Germany.
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Biskup T. Structure-Function Relationship of Organic Semiconductors: Detailed Insights From Time-Resolved EPR Spectroscopy. Front Chem 2019; 7:10. [PMID: 30775359 PMCID: PMC6367236 DOI: 10.3389/fchem.2019.00010] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Accepted: 01/07/2019] [Indexed: 11/22/2022] Open
Abstract
Organic photovoltaics (OPV) is a promising technology to account for the increasing demand for energy in form of electricity. Whereas the last decades have seen tremendous progress in the field witnessed by the steady increase in efficiency of OPV devices, we still lack proper understanding of fundamental aspects of light-energy conversion, demanding for systematic investigation on a fundamental level. A detailed understanding of the electronic structure of semiconducting polymers and their building blocks is essential to develop efficient materials for organic electronics. Illuminating conjugated polymers not only leads to excited states, but sheds light on some of the most important aspects of device efficiency in organic electronics as well. The interplay between electronic structure, morphology, flexibility, and local ordering, while at the heart of structure-function relationship of organic electronic materials, is still barely understood. (Time-resolved) electron paramagnetic resonance (EPR) spectroscopy is particularly suited to address these questions, allowing one to directly detect paramagnetic states and to reveal their spin-multiplicity, besides its clearly superior spectral resolution compared to optical methods. This article aims at giving a non-specialist audience an overview of what EPR spectroscopy and particularly its time-resolved variant (TREPR) can contribute to unraveling aspects of structure-function relationship in organic semiconductors.
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Affiliation(s)
- Till Biskup
- Institute of Physical Chemistry, University of Freiburg, Freiburg, Germany
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Meyer DL, Matsidik R, Fazzi D, Sommer M, Biskup T. Probing Exciton Delocalization in Organic Semiconductors: Insight from Time-Resolved Electron Paramagnetic Resonance and Magnetophotoselection Experiments. J Phys Chem Lett 2018; 9:7026-7031. [PMID: 30485108 DOI: 10.1021/acs.jpclett.8b03196] [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
Delocalization of excited states of organic semiconductors is directly related to their efficiency in devices. Time-resolved electron paramagnetic resonance spectroscopy provides unique capabilities in this respect because of its high spectral resolution and capability to probe the geometry and extent of excitons. Using magnetophotoselection experiments, the mode of exciton delocalization, along the backbone or parallel to the π-π stacking direction of the conjugated polymers, can be revealed. We demonstrate the robustness of this approach by applying it to building blocks of a prototypical conjugated polymer showing a symmetry of their excited states being far from ideal for this experiment. This renders magnetophotoselection superior to other approaches because it is applicable to a wealth of other organic semiconductors. The insight gained into exciton delocalization is crucial to the structure-function relationship of organic semiconductors and directly relevant for developing highly efficient materials.
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Affiliation(s)
- Deborah L Meyer
- Institut für Physikalische Chemie , Albert-Ludwigs-Universität Freiburg , 79104 Freiburg , Germany
| | - Rukiya Matsidik
- Institut für Makromolekulare Chemie , Albert-Ludwigs-Universität Freiburg , 79104 Freiburg , Germany
| | - Daniele Fazzi
- Institut für Physikalische Chemie , Universität zu Köln , 50939 Köln , Germany
| | - Michael Sommer
- Institut für Makromolekulare Chemie , Albert-Ludwigs-Universität Freiburg , 79104 Freiburg , Germany
- Institut für Chemie, Polymerchemie , Technische Universität Chemnitz , 09111 Chemnitz , Germany
| | - Till Biskup
- Institut für Physikalische Chemie , Albert-Ludwigs-Universität Freiburg , 79104 Freiburg , Germany
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Matt C, Meyer DL, Lombeck F, Sommer M, Biskup T. Different routes towards triplet states in organic semiconductors: direct S0→T excitation probed by time-resolved EPR spectroscopy. Mol Phys 2018. [DOI: 10.1080/00268976.2018.1523479] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Affiliation(s)
- Clemens Matt
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Deborah L. Meyer
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Florian Lombeck
- Institut für Makromolekulare Chemie, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Michael Sommer
- Institut für Makromolekulare Chemie, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
- Lehrstuhl Polymerchemie, Technische Universität Chemnitz, Chemnitz, Germany
| | - Till Biskup
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
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