1
|
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.
Collapse
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
| |
Collapse
|
2
|
Schötz K, Panzer F, Sommer M, Bässler H, Köhler A. A spectroscopic assessment of static and dynamic disorder in a film of a polythiophene with a planarized backbone. MATERIALS HORIZONS 2023; 10:5538-5546. [PMID: 37853812 DOI: 10.1039/d3mh01262j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2023]
Abstract
The optoelectronic performance of organic semiconductor devices is related to the static and dynamic disorder in the film. The disorder can be assessed by considering the linewidth of its optical spectra. We focus on identifying the effect of conjugation length distribution on the static energetic disorder. Hence, we disentangle the contributions of static and dynamic disorder to the absorption and emission spectra of poly(3-(2,5-dioctylphenyl)-thiophene) (PDOPT) by exploring how the linewidth and energy of the spectra evolve upon cooling the sample from 300 K to 5 K. PDOPT has sterically hindered side chains that arrange such as to cause a planarized polymer backbone. This makes it a suitable model for a quasi-one-dimensional molecular system. By modelling the conjugated segments as coupled oscillators we find that the linewidth contribution resulting from the variation of conjugation length decreases linearly with decreasing exciton energy and extrapolates to zero at the energy corresponding to an infinite chain. These results provide a new avenue to the design of low disorder and hence high mobility polymeric semiconductors.
Collapse
Affiliation(s)
- Konstantin Schötz
- Soft Matter Optoelectronics and Bavarian Polymer Institute (BPI), University of Bayreuth, Universitätsstr. 30, 95447 Bayreuth, Germany
| | - Fabian Panzer
- Soft Matter Optoelectronics and Bavarian Polymer Institute (BPI), University of Bayreuth, Universitätsstr. 30, 95447 Bayreuth, Germany
| | - Michael Sommer
- Institute for Chemistry, Chemnitz University of Technology, Straße der Nationen 62, 09111 Chemnitz, Germany
| | - Heinz Bässler
- Bayreuth Institute of Macromolecular Research (BIMF), University of Bayreuth, Universitätsstr. 30, 95447 Bayreuth, Germany.
| | - Anna Köhler
- Soft Matter Optoelectronics and Bavarian Polymer Institute (BPI), University of Bayreuth, Universitätsstr. 30, 95447 Bayreuth, Germany
- Bayreuth Institute of Macromolecular Research (BIMF), University of Bayreuth, Universitätsstr. 30, 95447 Bayreuth, Germany.
| |
Collapse
|
3
|
Wittmann B, Wiesneth S, Motamen S, Simon L, Serein-Spirau F, Reiter G, Hildner R. Energy transport and light propagation mechanisms in organic single crystals. J Chem Phys 2020; 153:144202. [PMID: 33086831 DOI: 10.1063/5.0019832] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Unambiguous information about spatiotemporal exciton dynamics in three-dimensional nanometer- to micrometer-sized organic structures is difficult to obtain experimentally. Exciton dynamics can be modified by annihilation processes, and different light propagation mechanisms can take place, such as active waveguiding and photon recycling. Since these various processes and mechanisms can lead to similar spectroscopic and microscopic signatures on comparable time scales, their discrimination is highly demanding. Here, we study individual organic single crystals grown from thiophene-based oligomers. We use time-resolved detection-beam scanning microscopy to excite a local singlet exciton population and monitor the subsequent broadening of the photoluminescence (PL) signal in space and on pico- to nanosecond time scales. Combined with Monte Carlo simulations, we were able to exclude photon recycling for our system, whereas leakage radiation upon active waveguiding leads to an apparent PL broadening of about 20% compared to the initial excitation profile. Exciton-exciton annihilation becomes important at high excitation fluence and apparently accelerates the exciton dynamics leading to apparently increased diffusion lengths. At low excitation fluences, the spatiotemporal PL broadening results from singlet exciton diffusion with diffusion lengths of up to 210 nm. Surprisingly, even in structurally highly ordered single crystals, the transport dynamics is subdiffusive and shows variations between different crystals, which we relate to varying degrees of static and dynamic electronic disorders.
Collapse
Affiliation(s)
- Bernd Wittmann
- Spectroscopy of Soft Matter, University of Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany
| | - Stephan Wiesneth
- Spectroscopy of Soft Matter, University of Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany
| | - Sajedeh Motamen
- Institute of Physics, University of Freiburg, Hermann-Herder-Straße 3, 79104 Freiburg, Germany
| | - Laurent Simon
- Université de Strasbourg (UdS)-Université de Haute Alsace (UHA), Institut de Science des Matériaux de Mulhouse (IS2M), UMR 7361-CNRS, 3bis rue Alfred Werner, 68093 Mulhouse, France
| | - Françoise Serein-Spirau
- Institut Charles Gerhardt de Montpellier, Université de Montpellier, Ecole Nationale Supérieure de Chimie de Montpellier, UMR 5353-CNRS, Equipe Architectures Moleculaires et Materiaux Nanostructures (AM2N), 8 Rue de l'Ecole Normale, 34090 Montpellier Cedex 05, France
| | - Günter Reiter
- Institute of Physics, University of Freiburg, Hermann-Herder-Straße 3, 79104 Freiburg, Germany
| | - Richard Hildner
- Spectroscopy of Soft Matter, University of Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany
| |
Collapse
|
4
|
Raithel D, Simine L, Pickel S, Schötz K, Panzer F, Baderschneider S, Schiefer D, Lohwasser R, Köhler J, Thelakkat M, Sommer M, Köhler A, Rossky PJ, Hildner R. Direct observation of backbone planarization via side-chain alignment in single bulky-substituted polythiophenes. Proc Natl Acad Sci U S A 2018; 115:2699-2704. [PMID: 29483262 PMCID: PMC5856543 DOI: 10.1073/pnas.1719303115] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The backbone conformation of conjugated polymers affects, to a large extent, their optical and electronic properties. The usually flexible substituents provide solubility and influence the packing behavior of conjugated polymers in films or in bad solvents. However, the role of the side chains in determining and potentially controlling the backbone conformation, and thus the optical and electronic properties on the single polymer level, is currently under debate. Here, we investigate directly the impact of the side chains by studying the bulky-substituted poly(3-(2,5-dioctylphenyl)thiophene) (PDOPT) and the common poly(3-hexylthiophene) (P3HT), both with a defined molecular weight and high regioregularity, using low-temperature single-chain photoluminescence (PL) spectroscopy and quantum-classical simulations. Surprisingly, the optical transition energy of PDOPT is significantly (∼2,000 cm-1 or 0.25 eV) red-shifted relative to P3HT despite a higher static and dynamic disorder in the former. We ascribe this red shift to a side-chain induced backbone planarization in PDOPT, supported by temperature-dependent ensemble PL spectroscopy. Our atomistic simulations reveal that the bulkier 2,5-dioctylphenyl side chains of PDOPT adopt a clear secondary helical structural motif and thus protect conjugation, i.e., enforce backbone planarity, whereas, for P3HT, this is not the case. These different degrees of planarity in both thiophenes do not result in different conjugation lengths, which we found to be similar. It is rather the stronger electronic coupling between the repeating units in the more planar PDOPT which gives rise to the observed spectral red shift as well as to a reduced calculated electron-hole polarization.
Collapse
Affiliation(s)
- Dominic Raithel
- Experimental Physics IV, University of Bayreuth, 95440 Bayreuth, Germany
| | - Lena Simine
- Department of Chemistry, Rice University, Houston, TX 77005
| | - Sebastian Pickel
- Experimental Physics IV, University of Bayreuth, 95440 Bayreuth, Germany
| | - Konstantin Schötz
- Experimental Physics II, University of Bayreuth, 95440 Bayreuth, Germany
| | - Fabian Panzer
- Experimental Physics II, University of Bayreuth, 95440 Bayreuth, Germany
| | | | - Daniel Schiefer
- Institute of Macromolecular Chemistry, University of Freiburg, 79104 Freiburg, Germany
| | - Ruth Lohwasser
- Applied Functional Polymers, University of Bayreuth, 95440 Bayreuth, Germany
| | - Jürgen Köhler
- Experimental Physics IV, University of Bayreuth, 95440 Bayreuth, Germany
- Bayreuth Institute of Macromolecular Research, University of Bayreuth, 95440 Bayreuth, Germany
| | - Mukundan Thelakkat
- Applied Functional Polymers, University of Bayreuth, 95440 Bayreuth, Germany
| | - Michael Sommer
- Institute of Macromolecular Chemistry, University of Freiburg, 79104 Freiburg, Germany
| | - Anna Köhler
- Experimental Physics II, University of Bayreuth, 95440 Bayreuth, Germany
- Bayreuth Institute of Macromolecular Research, University of Bayreuth, 95440 Bayreuth, Germany
| | - Peter J Rossky
- Department of Chemistry, Rice University, Houston, TX 77005
| | - Richard Hildner
- Experimental Physics IV, University of Bayreuth, 95440 Bayreuth, Germany;
| |
Collapse
|
5
|
Jiang Y, McNeill J. Light-Harvesting and Amplified Energy Transfer in Conjugated Polymer Nanoparticles. Chem Rev 2016; 117:838-859. [DOI: 10.1021/acs.chemrev.6b00419] [Citation(s) in RCA: 168] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- Yifei Jiang
- Department of Chemistry, Clemson University, Clemson, South Carolina 29634, United States
| | - Jason McNeill
- Department of Chemistry, Clemson University, Clemson, South Carolina 29634, United States
| |
Collapse
|
6
|
Raithel D, Baderschneider S, de Queiroz TB, Lohwasser R, Köhler J, Thelakkat M, Kümmel S, Hildner R. Emitting Species of Poly(3-hexylthiophene): From Single, Isolated Chains to Bulk. Macromolecules 2016. [DOI: 10.1021/acs.macromol.6b02077] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
| | | | - Thiago B. de Queiroz
- Centro
de Ciências Naturais e Humanas, Universidade Federal do ABC, 09510-580, Santo André-SP, Brazil
| | | | | | | | | | | |
Collapse
|
7
|
Baderschneider S, Scherf U, Köhler J, Hildner R. Influence of the Conjugation Length on the Optical Spectra of Single Ladder-Type (p-Phenylene) Dimers and Polymers. J Phys Chem A 2016; 120:233-40. [PMID: 26696134 DOI: 10.1021/acs.jpca.5b10879] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We employ low-temperature single-molecule photoluminescence spectroscopy on a π-conjugated ladder-type (p-phenylene) dimer and the corresponding polymer methyl-substituted ladder-type poly(p-phenylene), MeLPPP, to study the impact of the conjugation length (π-electron delocalization) on their optical properties on a molecular scale. Our data show that the linear electron-phonon coupling to intramolecular vibrational modes is very sensitive to the conjugation length, a well-known behavior of organic (macro-) molecules. In particular, the photoluminescence spectra of single dimers feature a rather strong low-energy (150 cm(-1)) skeletal mode of the backbone, which does not appear in the spectra of individual chromophores on single MeLPPP chains. We attribute this finding to a strongly reduced electron-phonon coupling strength and/or vibrational energy of this mode for MeLPPP with its more delocalized π-electron system as compared to the dimer. In contrast, the line widths of the purely electronic zero-phonon lines (ZPL) in single-molecule spectra do not show differences between the dimer and MeLPPP; for both systems the ZPLs are apparently broadened by fast unresolved spectral diffusion. Finally, we demonstrate that the low-temperature ensemble photoluminescence spectrum of the dimer cannot be reproduced by the distribution of spectral positions of the ZPLs. The dimer's bulk spectrum is rather apparently broadened by electron-phonon coupling to the low-energy skeletal mode, whereas for MeLPPP the inhomogeneous bulk line shape resembles the distribution of spectral positions of the ZPLs of single chromophores.
Collapse
Affiliation(s)
- Sebastian Baderschneider
- Experimentalphysik IV and Bayreuth Institute for Macromolecular Research (BIMF), Universität Bayreuth , 95440 Bayreuth, Germany
| | - Uli Scherf
- Fachbereich C - Mathematik und Naturwissenschaften and Institut für Polymertechnologie, Universität Wuppertal , Gauss-Strasse 20, 42097 Wuppertal, Germany
| | - Jürgen Köhler
- Experimentalphysik IV and Bayreuth Institute for Macromolecular Research (BIMF), Universität Bayreuth , 95440 Bayreuth, Germany
| | - Richard Hildner
- Experimentalphysik IV and Bayreuth Institute for Macromolecular Research (BIMF), Universität Bayreuth , 95440 Bayreuth, Germany
| |
Collapse
|
8
|
Barisien T, Legrand L, Mu Z, Hameau S. Excitonic linewidth of organic quantum wires generated in reduced dimensionality matrices. Phys Chem Chem Phys 2016; 18:12928-37. [DOI: 10.1039/c6cp00629a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Nanostructured crystalline film achieving a 2D bath for single conjugated polymer chain linewidth spectroscopy.
Collapse
Affiliation(s)
- Thierry Barisien
- Sorbonne Universités
- UPMC Université Paris 06
- CNRS-UMR 7588
- Institut des NanoSciences de Paris
- Paris
| | - Laurent Legrand
- Sorbonne Universités
- UPMC Université Paris 06
- CNRS-UMR 7588
- Institut des NanoSciences de Paris
- Paris
| | - Zhao Mu
- Sorbonne Universités
- UPMC Université Paris 06
- CNRS-UMR 7588
- Institut des NanoSciences de Paris
- Paris
| | - Sophie Hameau
- Sorbonne Universités
- UPMC Université Paris 06
- CNRS-UMR 7588
- Institut des NanoSciences de Paris
- Paris
| |
Collapse
|
9
|
Single Molecule Studies of a Ladder Type Conjugated Polymer: Vibronic Spectra, Line Widths, and Energy Transfer. Macromol Rapid Commun 2015; 36:1096-102. [DOI: 10.1002/marc.201400739] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2014] [Revised: 02/25/2015] [Indexed: 11/07/2022]
|
10
|
Yang J, Ham S, Kim TW, Park KH, Nakao K, Shimizu H, Iyoda M, Kim D. Inhomogeneity in the excited-state torsional disorder of a conjugated macrocycle. J Phys Chem B 2015; 119:4116-26. [PMID: 25700008 DOI: 10.1021/jp5123689] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The photophysics of conjugated polymers has generally been explained based on the interactions between the component conjugated chromophores in a tangled chain. However, conjugated chromophores are entities with static and dynamic structural disorder, which directly affects the conjugated polymer photophysics. Here we demonstrate the impact of chain structure torsional disorder on the spectral characteristics for a macrocyclic oligothiophene 1, which is obscured in conventional linear conjugated chromophores by diverse structural disorders such as those in chromophore size and shape. We used simultaneous multiple fluorescence parameter measurement for a single molecule and quantum-mechanical calculations to show that within the fixed conjugation length across the entire ring an inhomogeneity from torsional disorder in the structure of 1 plays a crucial role in causing its energetic disorder, which affords the spectral broadening of ∼220 meV. The torsional disorder in 1 fluctuated on the time scale of hundreds of milliseconds, typically accompanied by spectral drifts on the order of ∼10 meV. The fluctuations could generate torsional defects and change the electronic structure of 1 associated with the ring symmetry. These findings disclose the fundamental nature of conjugated chromophore that is the most elementary spectroscopic unit in conjugated polymers and suggest the importance of engineering structural disorder to optimize polymer-based device photophysics. Additionally, we combined defocused wide-field fluorescence microscopy and linear dichroism obtained from the simultaneous measurements to show that 1 emits polarized light with a changing polarization direction based on the torsional disorder fluctuations.
Collapse
Affiliation(s)
- Jaesung Yang
- Spectroscopy Laboratory for Functional π-Electronic Systems and Department of Chemistry, Yonsei University , Seoul 120-749, Korea
| | | | | | | | | | | | | | | |
Collapse
|
11
|
Kunz R, Timpmann K, Southall J, Cogdell RJ, Freiberg A, Köhler J. Fluctuations in the Electron-Phonon Coupling of a Single Chromoprotein. Angew Chem Int Ed Engl 2013; 52:8726-30. [DOI: 10.1002/anie.201303231] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Revised: 05/22/2013] [Indexed: 10/26/2022]
|
12
|
Kunz R, Timpmann K, Southall J, Cogdell RJ, Freiberg A, Köhler J. Fluctuations in the Electron-Phonon Coupling of a Single Chromoprotein. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201303231] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
13
|
Da Como E, Borys NJ, Strohriegl P, Walter MJ, Lupton JM. Formation of a Defect-Free π-Electron System in Single β-Phase Polyfluorene Chains. J Am Chem Soc 2011; 133:3690-2. [DOI: 10.1021/ja109342t] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Enrico Da Como
- Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84112, United States
| | - Nicholas J. Borys
- Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84112, United States
| | - Peter Strohriegl
- Makromolekulare Chemie I, University of Bayreuth, 95440 Bayreuth, Germany
| | - Manfred J. Walter
- Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84112, United States
| | - John M. Lupton
- Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84112, United States
| |
Collapse
|
14
|
Schindler F, Lupton JM. Electrothermal manipulation of individual chromophores in single conjugated polymer chains: controlling intrachain FRET, blinking, and spectral diffusion. NANO LETTERS 2010; 10:2683-2689. [PMID: 20536210 DOI: 10.1021/nl101526p] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Single molecule spectroscopy of individual chains of a conjugated polymer opens up deep insight into electronic localization phenomena, which govern the underlying optical properties of these complex and disordered materials. We explore the nature of a single chromophore arising in a delocalized pi-electron system by applying periodic electrothermal perturbations at low temperatures. Brief heating of the chromophore leads to a dramatic increase in the transition line width and is generally accompanied by a random jump of the emission energy. This observation demonstrates that chromophores on a polymer chain are not only defined by structural disorder but also by the subtleties of the local dielectric environment. The effect of thermal perturbation becomes more complex when long polymer chains are considered, which can potentially support the formation of multiple chromophores. Here, a momentary increase in temperature can promote intrachain energy transfer to quenching sites, leading to a strong modulation of emission intensity with temperature. Unexpectedly, such energy transfer can serve to either raise or lower the transition line width and quantum yield of the ensemble with increasing temperature, depending on the specific energetics of the chromophores in the system, which in turn vary with time. The controlled perturbation of both the emission spectrum and the intensity by brief heating of the polymer chain offers insight into possible microscopic origins of fluorescence blinking and spectral diffusion, which ultimately impact on the efficiency and spectral purity of devices.
Collapse
Affiliation(s)
- Florian Schindler
- Department of Physics, Ludwig-Maximilians University of Munich, Munich, Germany
| | | |
Collapse
|