1
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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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Eder T, Kraus D, Höger S, Vogelsang J, Lupton JM. Vibrations Responsible for Luminescence from HJ-Aggregates of Conjugated Polymers Identified by Cryogenic Spectroscopy of Single Nanoparticles. ACS NANO 2022; 16:6382-6393. [PMID: 35394735 DOI: 10.1021/acsnano.2c00472] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
A single polymer chain can be thought of as a covalently bound J-aggregate, where the microscopic transition-dipole moments line up to emit in phase. Packing polymer chains into a bulk film can result in the opposite effect, inducing H-type coupling between chains. Cofacial transition-dipole moments oscillate out of phase, canceling each other out, so that the lowest-energy excited state turns dark. H-aggregates of conjugated polymers can, in principle, be coaxed into emitting light by mixing purely electronic and vibronic transitions. However, it is challenging to characterize this electron-phonon coupling experimentally. In a bulk film, many different conformations exist with varying degrees of intrachain J-type and interchain H-type coupling strengths, giving rise to broad and featureless aggregate absorption and emission spectra. Even if single nanoparticles consisting of only a few single chains are grown in a controlled fashion, the luminescence spectra remain broad, owing to the underlying molecular dynamics and structural heterogeneity at room temperature. At cryogenic temperatures, emission from H-type aggregates should be suppressed because, in the absence of thermal energy, internal conversion drives the aggregate to the lowest-energy dark state. At the same time, electronic and vibronic transitions narrow substantially, facilitating the attribution of spectral signatures to distinct vibrational modes. We demonstrate how to distinguish signatures of interchain H-type aggregate species from those of intramolecular J-type coupling. Whereas all dominant vibronic modes revealed in the photoluminescence (PL) and surface-enhanced resonance Raman scattering spectra of a single chromophore within a single polymer chain are identified in the J-type aggregate luminescence spectra, they are not all present at once in the H-type spectra. Universal spectral features are found for the luminescence from strongly HJ-coupled chains, clearly resolving the vibrations responsible for the nonadiabatic excited-state molecular dynamics that enable light emission. We discuss the possible combinations of vibrational modes responsible for H-type aggregate PL and demonstrate that only one, mainly the lowest energy one, of the three dominant vibrational modes contributes to the 0-1 transition, whereas combinations of all three are found in the 0-2 transition. From this analysis, we can distinguish between energy shifts due to either J-type intrachain coupling or H-type interchain interactions, offering a means to directly discriminate between structural and energetic disorder.
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Affiliation(s)
- Theresa Eder
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg, Universitätsstrasse 31, 93040 Regensburg, Germany
| | - Daniel Kraus
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg, Universitätsstrasse 31, 93040 Regensburg, Germany
| | - Sigurd Höger
- Kekulé-Institut für Organische Chemie und Biochemie der Universität Bonn, Gerhard-Domagk-Str. 1, 53121 Bonn, Germany
| | - Jan Vogelsang
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg, Universitätsstrasse 31, 93040 Regensburg, Germany
| | - John M Lupton
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg, Universitätsstrasse 31, 93040 Regensburg, Germany
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3
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Peteanu LA, Chowdhury S, Wildeman J, Sfeir MY. Exciton–Exciton Annihilation as a Probe of Interchain Interactions in PPV–Oligomer Aggregates. J Phys Chem B 2017; 121:1707-1714. [DOI: 10.1021/acs.jpcb.6b11250] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Linda A. Peteanu
- Department
of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States
| | - Sanchari Chowdhury
- Department
of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States
| | - Jurjen Wildeman
- Zernike Institute of Advanced Materials, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Matthew Y. Sfeir
- Center
for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, United States
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4
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Abstract
Organic (opto)electronic materials have received considerable attention due to their applications in thin-film-transistors, light-emitting diodes, solar cells, sensors, photorefractive devices, and many others. The technological promises include low cost of these materials and the possibility of their room-temperature deposition from solution on large-area and/or flexible substrates. The article reviews the current understanding of the physical mechanisms that determine the (opto)electronic properties of high-performance organic materials. The focus of the review is on photoinduced processes and on electronic properties important for optoelectronic applications relying on charge carrier photogeneration. Additionally, it highlights the capabilities of various experimental techniques for characterization of these materials, summarizes top-of-the-line device performance, and outlines recent trends in the further development of the field. The properties of materials based both on small molecules and on conjugated polymers are considered, and their applications in organic solar cells, photodetectors, and photorefractive devices are discussed.
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Affiliation(s)
- Oksana Ostroverkhova
- Department of Physics, Oregon State University , Corvallis, Oregon 97331, United States
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5
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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.
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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
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6
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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.
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Affiliation(s)
- Jaesung Yang
- Spectroscopy Laboratory for Functional π-Electronic Systems and Department of Chemistry, Yonsei University , Seoul 120-749, Korea
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7
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Martin TP, Wise AJ, Busby E, Gao J, Roehling JD, Ford MJ, Larsen DS, Moulé AJ, Grey JK. Packing dependent electronic coupling in single poly(3-hexylthiophene) H- and J-aggregate nanofibers. J Phys Chem B 2012; 117:4478-87. [PMID: 23214454 DOI: 10.1021/jp308586k] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Nanofibers (NFs) of the prototype conjugated polymer, poly(3-hexylthiophene) (P3HT), displaying H- and J-aggregate character are studied using temperature- and pressure-dependent photoluminescence (PL) spectroscopy. Single J-aggregate NF spectra show a decrease of the 0-0/0-1 vibronic intensity ratio from ~2.0 at 300 K to ~1.3 at 4 K. Temperature-dependent PL line shape parameters (i.e., 0-0 energies and 0-0/0-1 intensity ratios) undergo an abrupt change in the range of ~110-130 K suggesting a change in NF chain packing. Pressure-dependent PL lifetimes also show increased contributions from an instrument-limited decay component which is attributed to greater torsional disorder of the P3HT backbone upon decreasing NF volume. It is proposed that the P3HT alkyl side groups change their packing arrangement from a type I to type II configuration causing a decrease in J-aggregate character (lower intrachain order) in both temperature- and pressure-dependent PL spectra. Chain packing dependent exciton and polaron relaxation and recombination dynamics in NF aggregates are next studied using transient absorption spectroscopy (TAS). TAS data reveal faster polaron recombination dynamics in H-type P3HT NFs indicative of interchain delocalization whereas J-type NFs exhibit delayed recombination suggesting that polarons (in addition to excitons) are more delocalized along individual chains. Both time-resolved and steady-state spectra confirm that excitons and polarons in J-type NFs are predominantly intrachain in nature that can acquire interchain character with small structural (chain packing) perturbations.
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Affiliation(s)
- Thomas P Martin
- Department of Chemistry and Chemical Biology, MSC03 2060, University of New Mexico, Albuquerque, New Mexico 87131, USA
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8
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Li Y, Liu J, Liu B, Tomczak N. Highly emissive PEG-encapsulated conjugated polymer nanoparticles. NANOSCALE 2012; 4:5694-5702. [PMID: 22878417 DOI: 10.1039/c2nr31267k] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
A novel bioimaging probe based on a conjugated polymer, poly(9,9-dihexylfluorene-alt-2,1,3-benzoxadiazole) (PFBD), is demonstrated. Transfer of the hydrophobic polymer into water using a short chain poly(ethylene glycol) (PEG) resulted in conjugated polymer nanoparticles (PEG-PFBD) with a fluorescence quantum yield of 46%. The PEG-PFBD nanoparticles possessed several desirable structural and photophysical properties, such as colloidal stability in a broad range of pH values, sub-20 nm particle size, the presence of surface chemical functionality, as well as desirable excitation and emission spectra, for bioimaging applications. PEG-PFBD nanoparticles were conjugated with cyclic RGDfK targeting peptide for labeling of membrane α(V)β(3) integrin receptors on live HT-29 adenocarcinoma cells. Single nanoparticle microscopy revealed that the PEG-capped PFBD nanoparticles exhibit at least ten times higher emitted photon counts than single quantum dots (QD655) of comparable size. In addition, Fluorescence Lifetime Imaging Microscopy (FLIM) of single PEG-PFBD nanoparticles revealed that the nanoparticles display a clearly resolvable single nanoparticle fluorescence lifetime.
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Affiliation(s)
- Yuqiong Li
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research, 3 Research Link, Singapore 117602
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9
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Khalil GE, Adawi AM, Robinson B, Cadby AJ, Tsoi W, Kim JS, Charas A, Morgado J, Lidzey DG. Spectroscopy and Single-Molecule Emission of a Fluorene-Terthiophene Oligomer. J Phys Chem B 2011; 115:12028-35. [DOI: 10.1021/jp206368g] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- G. E. Khalil
- Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH, United Kingdom
- National Institute of Laser Enhanced Science (NILES), Cairo University, Cairo, Egypt
| | - A. M. Adawi
- Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH, United Kingdom
| | - B. Robinson
- Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH, United Kingdom
| | - A. J. Cadby
- Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH, United Kingdom
| | - W.C. Tsoi
- The Blackett Laboratory, Imperial College, Prince Consort Road, London SW7 2BZ, United Kingdom
| | - J-S. Kim
- The Blackett Laboratory, Imperial College, Prince Consort Road, London SW7 2BZ, United Kingdom
| | - A. Charas
- Instituto de Telecomunicações, Av. Rovisco Pais, P-1049-001 Lisboa, Portugal
| | - J. Morgado
- Instituto de Telecomunicações, Av. Rovisco Pais, P-1049-001 Lisboa, Portugal
| | - D. G. Lidzey
- Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH, United Kingdom
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10
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Feist FA, Zickler MF, Basché T. Origin of the Red Sites and Energy Transfer Rates in Single MEH-PPV Chains at Low Temperature. Chemphyschem 2011; 12:1499-508. [DOI: 10.1002/cphc.201001010] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2010] [Indexed: 11/10/2022]
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11
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Barford W, Lidzey DG, Makhov DV, Meijer AJH. Exciton localization in disordered poly(3-hexylthiophene). J Chem Phys 2010; 133:044504. [PMID: 20687660 DOI: 10.1063/1.3459099] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Singlet exciton localization in conformationally disordered poly(3-hexylthiophene) (P3HT) is investigated via configuration interaction (singles) calculations of the Pariser-Parr-Pople model. The P3HT structures are generated by molecular dynamics simulations. The lowest-lying excitons are spatially localized, space filling, and nonoverlapping. These define spectroscopic segments or chromophores. The strong conformational disorder in P3HT causes breaks in the pi-conjugation. Depending on the relative values of the disorder-induced localization length and the distances between the pi-conjugation breaks, these breaks sometimes serve to pin the low-lying localized excitons. The exciton confinement also causes a local spectrum of low-lying exciton states. Coulomb-induced intra- or interchain interactions between spectroscopic segments in close spatial proximity can delocalize an exciton across these segments, in principle causing phase coherent transition dipole moments.
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Affiliation(s)
- William Barford
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, Oxford OX1 3QZ, United Kingdom.
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12
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Banerji N, Cowan S, Leclerc M, Vauthey E, Heeger AJ. Exciton formation, relaxation, and decay in PCDTBT. J Am Chem Soc 2010; 132:17459-70. [PMID: 21087001 DOI: 10.1021/ja105290e] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The nature and time evolution of the primary excitations in the pristine conjugated polymer, PCDTBT, are investigated by femtosecond-resolved fluorescence up-conversion spectroscopy. The extensive study includes data from PCDTBT thin film and from PCDTBT in chlorobenzene solution, compares the fluorescence dynamics for several excitation and emission wavelengths, and is complemented by polarization-sensitive measurements. The results are consistent with the photogeneration of mobile electrons and holes by interband π-π* transitions, which then self-localize within about 100 fs and evolve to a bound singlet exciton state in less than 1 ps. The excitons subsequently undergo successive migrations to lower energy localized states, which exist as a result of disorder. In parallel, there is also slow conformational relaxation of the polymer backbone. While the initial self-localization occurs faster than the time resolution of our experiment, the exciton formation, exciton migration, and conformational changes lead to a progressive relaxation of the inhomogeneously broadened emission spectrum with time constants ranging from about 500 fs to tens of picoseconds. The time scales found here for the relaxation processes in pristine PCDTBT are compared to the time scale (<0.2 ps) previously reported for photoinduced charge transfer in phase-separated PCDTBT:fullerene blends (Phys. Rev. B 2010, 81, 125210). We point out that exciton formation and migration in PCDTBT occur at times much longer than the ultrafast photoinduced electron transfer time in PCDTBT:fullerene blends. This disparity in time scales is not consistent with the commonly proposed idea that photoinduced charge separation occurs after diffusion of the polymer exciton to a fullerene interface. We therefore discuss alternative mechanisms that are consistent with ultrafast charge separation before localization of the primary excitation to form a bound exciton.
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Affiliation(s)
- Natalie Banerji
- Center for Polymers and Organic Solids, University of California at Santa Barbara, Santa Barbara, California 93106-5090, USA
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13
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Lupton JM. Single-molecule spectroscopy for plastic electronics: materials analysis from the bottom-up. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2010; 22:1689-721. [PMID: 20496402 DOI: 10.1002/adma.200902306] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
pi-conjugated polymers find a range of applications in electronic devices. These materials are generally highly disordered in terms of chain length and chain conformation, besides being influenced by a variety of chemical and physical defects. Although this characteristic can be of benefit in certain device applications, disorder severely complicates materials analysis. Accurate analytical techniques are, however, crucial to optimising synthetic procedures and assessing overall material purity. Fortunately, single-molecule spectroscopic techniques have emerged as an unlikely but uniquely powerful approach to unraveling intrinsic material properties from the bottom up. Building on the success of such techniques in the life sciences, single-molecule spectroscopy is finding increasing applicability in materials science, effectively enabling the dissection of the bulk down to the level of the individual molecular constituent. This article reviews recent progress in single molecule spectroscopy of conjugated polymers as used in organic electronics.
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Affiliation(s)
- John M Lupton
- Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112, USA.
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14
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Lin H, Hania RP, Bloem R, Mirzov O, Thomsson D, Scheblykin IG. Single chain versus single aggregate spectroscopy of conjugated polymers. Where is the border? Phys Chem Chem Phys 2010; 12:11770-7. [DOI: 10.1039/c001120g] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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15
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Lin H, Tian Y, Zapadka K, Persson G, Thomsson D, Mirzov O, Larsson PO, Widengren J, Scheblykin IG. Fate of excitations in conjugated polymers: single-molecule spectroscopy reveals nonemissive "dark" regions in MEH-PPV individual chains. NANO LETTERS 2009; 9:4456-4461. [PMID: 19860455 DOI: 10.1021/nl9027473] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Single chains of the conjugated polymer MEH-PPV (poly(2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene)) were studied with wide-field fluorescence microscopy (dispersion in inert polymer matrices) and with fluorescence correlation spectroscopy (chloroform solution). The fluorescence yield of individual molecules in matrices was found to be 1-2 orders of magnitude lower than that in solution and it decreased substantially with increasing chain length. It suggests that isolation of MEH-PPV molecules in polymer matrices creates favorable conditions for photogeneration of nonemissive primary excited states.
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Affiliation(s)
- Hongzhen Lin
- Chemical Physics and Pure and Applied Biochemistry, Lund University, Box 124, 22100 Lund, Sweden
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16
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Laquai F, Park YS, Kim JJ, Basché T. Excitation Energy Transfer in Organic Materials: From Fundamentals to Optoelectronic Devices. Macromol Rapid Commun 2009; 30:1203-31. [DOI: 10.1002/marc.200900309] [Citation(s) in RCA: 163] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2009] [Accepted: 05/12/2009] [Indexed: 11/09/2022]
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17
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Khalil GE, Adawi AM, Fox AM, Iraqi A, Lidzey DG. Single molecule spectroscopy of red- and green-emitting fluorene-based copolymers. J Chem Phys 2009; 130:044903. [DOI: 10.1063/1.3054142] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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18
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De Leener C, Hennebicq E, Sancho-Garcia JC, Beljonne D. Modeling the Dynamics of Chromophores in Conjugated Polymers: The Case of Poly(2-methoxy-5-(2′-ethylhexyl)oxy 1,4-phenylene vinylene) (MEH-PPV). J Phys Chem B 2009; 113:1311-22. [DOI: 10.1021/jp8029902] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Caroline De Leener
- Laboratory for Chemistry of Novel Materials, University of Mons-Hainaut, 20 Place du Parc, B-7000 Mons, Belgium, and Departamento de Química Física, Universidad de Alicante, E-03080 Alicante, Spain
| | - Emmanuelle Hennebicq
- Laboratory for Chemistry of Novel Materials, University of Mons-Hainaut, 20 Place du Parc, B-7000 Mons, Belgium, and Departamento de Química Física, Universidad de Alicante, E-03080 Alicante, Spain
| | - Juan-Carlos Sancho-Garcia
- Laboratory for Chemistry of Novel Materials, University of Mons-Hainaut, 20 Place du Parc, B-7000 Mons, Belgium, and Departamento de Química Física, Universidad de Alicante, E-03080 Alicante, Spain
| | - David Beljonne
- Laboratory for Chemistry of Novel Materials, University of Mons-Hainaut, 20 Place du Parc, B-7000 Mons, Belgium, and Departamento de Química Física, Universidad de Alicante, E-03080 Alicante, Spain
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19
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Triplet level-dependent photoluminescence and photoconduction properties of π-conjugated polymer thin films doped by iridium complexes. J Photochem Photobiol A Chem 2008. [DOI: 10.1016/j.jphotochem.2008.08.019] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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20
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Di Paolo RE, Gigante B, Esteves MA, Pires N, Santos C, Lameiro MH, Seixas de Melo J, Burrows HD, Maçanita AL. Picosecond Structural Relaxation of Abietic Acid Based Amine End CappedPara-Phenylenevinylene Trimers in Solution. Chemphyschem 2008; 9:2214-20. [DOI: 10.1002/cphc.200800374] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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21
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Feist FA, Basché T. Fluorescence Excitation and Emission Spectroscopy on Single MEH-PPV Chains at Low Temperature. J Phys Chem B 2008; 112:9700-8. [DOI: 10.1021/jp802585m] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Florian A. Feist
- Institut für Physikalische Chemie, Johannes Gutenberg-Universität, 55099 Mainz, Germany
| | - Thomas Basché
- Institut für Physikalische Chemie, Johannes Gutenberg-Universität, 55099 Mainz, Germany
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22
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Lin H, Tabaei SR, Thomsson D, Mirzov O, Larsson PO, Scheblykin IG. Fluorescence Blinking, Exciton Dynamics, and Energy Transfer Domains in Single Conjugated Polymer Chains. J Am Chem Soc 2008; 130:7042-51. [DOI: 10.1021/ja800153d] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Hongzhen Lin
- Chemical Physics and Pure and Applied Biochemistry, Lund University, Box 124, 22100 Lund, Sweden
| | - Seyed R. Tabaei
- Chemical Physics and Pure and Applied Biochemistry, Lund University, Box 124, 22100 Lund, Sweden
| | - Daniel Thomsson
- Chemical Physics and Pure and Applied Biochemistry, Lund University, Box 124, 22100 Lund, Sweden
| | - Oleg Mirzov
- Chemical Physics and Pure and Applied Biochemistry, Lund University, Box 124, 22100 Lund, Sweden
| | - Per-Olof Larsson
- Chemical Physics and Pure and Applied Biochemistry, Lund University, Box 124, 22100 Lund, Sweden
| | - Ivan G. Scheblykin
- Chemical Physics and Pure and Applied Biochemistry, Lund University, Box 124, 22100 Lund, Sweden
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23
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Di Paolo RE, Seixas de Melo J, Pina J, Burrows HD, Morgado J, Maçanita AL. Conformational Relaxation ofp-Phenylenevinylene Trimers in Solution Studied by Picosecond Time-Resolved Fluorescence. Chemphyschem 2007; 8:2657-64. [DOI: 10.1002/cphc.200700548] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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24
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Wang Z, Rothberg LJ. Structure and dynamics of single conjugated polymer chromophores by surface-enhanced Raman spectroscopy. ACS NANO 2007; 1:299-306. [PMID: 19206680 DOI: 10.1021/nn700213t] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Dramatic localization of optical fields by interactions with surface plasmons on nanotextured metal surfaces allows us to record Raman spectra of individual chromophores on single chains of a high-molecular-weight model conjugated polymer, poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene. The data are broadly consistent with two configurations of the chromophore that are characteristic of packed and loose conformations of the backbone. Within these types, fluctuations of the chromophore planarity are observed, and we show how they can be analyzed by studying the temporal correlation of successive spectra. Chromophores exhibit some configurational memory on the time scale of minutes. We also observe substantial spectral fluctuations and associate these mostly with thermally induced motions of the chromophore in the "hot spot". However, we also provide instances of data representing irreversible photochemistry as well as charging and discharging of the chromophore. Finally, we show that single chromophores embedded in the polymer reorganize in response to poor solvents.
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Affiliation(s)
- Zhenjia Wang
- Department of Chemistry, University of Rochester, Rochester, NY 14627, USA
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25
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Sugimoto T, Ebihara Y, Ogino K, Vacha M. Structure-Dependent Photophysics Studied in Single Molecules of Polythiophene Derivatives. Chemphyschem 2007; 8:1623-8. [PMID: 17577905 DOI: 10.1002/cphc.200700277] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We report on the photophysical characterization at the single-molecule level of a graft copolymer consisting of a polythiophene backbone and long polystyrene branches. The presence of the branches prevents the polymer chain from forming a collapsed conformational state. The photophysical properties of the resulting solution-like conformation are studied by measuring single-molecule photobleaching dynamics, emission polarization anisotropy and emission spectra. The results are compared with those obtained on the same polythiophene derivative without the branches. It is found that the presence of the branches is a decisive factor in determining the photophysical properties of the polymers on the single-molecule level.
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Affiliation(s)
- Toshikazu Sugimoto
- Department of Organic and Polymeric Materials, Tokyo Institute of Technology, Ookayama 2-12-1-S8, Meguro-ku, Tokyo 152-8552, Japan
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26
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Zhang L, Aite S, Yu Z. Unique laser-scanning optical microscope for low-temperature imaging and spectroscopy. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2007; 78:083701. [PMID: 17764323 DOI: 10.1063/1.2768924] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Low-temperature optical characterization of single quantum nanostructures can reveal detailed information on structure-dependent properties of these materials. We describe the development of a unique laser-scanning optical microscope capable of low-temperature single molecule/particle imaging and spectroscopy. Making use of the magnification of a microscope objective, the laser- scanning scheme of the present microscope allows for high-repeatability imaging over large sample areas. The microscope is utilized to measure the low-temperature Raman scattering spectra of individual single-walled carbon nanotubes and single molecule fluorescence spectra of conjugated polymers. The developed low-temperature microscope can be applied to study a wide array of nanomaterials at a single particle level.
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Affiliation(s)
- Li Zhang
- Department of Chemistry, City College of New York, New York, NY 10031, USA
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27
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Scheblykin IG, Yartsev A, Pullerits T, Gulbinas V, Sundström V. Excited State and Charge Photogeneration Dynamics in Conjugated Polymers. J Phys Chem B 2007; 111:6303-21. [PMID: 17521181 DOI: 10.1021/jp068864f] [Citation(s) in RCA: 217] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Conjugated polymers are becoming interesting materials for a range of optoelectronic applications. However, their often complex electronic and structural properties prevent establishment of straightforward property-function relationships. In this paper, we summarize recent results on the photophysics and excited state dynamics of conjugated polymers, in order to paint a picture of exciton formation, quenching, and generation of charge carriers.
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Affiliation(s)
- Ivan G Scheblykin
- Department of Chemical Physics, Lund University, Box 124, 221 00 Lund, Sweden
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28
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Feist FA, Tommaseo G, Basché T. Observation of very narrow linewidths in the fluorescence excitation spectra of single conjugated polymer chains at 1.2 K. PHYSICAL REVIEW LETTERS 2007; 98:208301. [PMID: 17677744 DOI: 10.1103/physrevlett.98.208301] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2007] [Indexed: 05/16/2023]
Abstract
Fluorescence emission and excitation spectra of single poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] polymer molecules embedded in poly(methylmethacrylate) have been recorded at 1.2 K. The ubiquitous spectral diffusion causes large variations in the spectral shape and apparent linewidth in the emission spectra. Nevertheless, we find very narrow (approximately 0.1 cm(-1)) purely electronic zero-phonon lines in the excitation spectra, which are 2 orders of magnitude smaller than previous estimates of the homogeneous linewidth. These results complement the molecular description of the low energy transitions in conjugated polymers.
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Affiliation(s)
- Florian A Feist
- Institut für Physikalische Chemie, Johannes Gutenberg-Universität, 55099 Mainz, Germany
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29
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Forster M, Thomsson D, Hania PR, Scheblykin IG. Redistribution of emitting state population in conjugated polymers probed by single-molecule fluorescence polarization spectroscopy. Phys Chem Chem Phys 2007; 9:761-6. [PMID: 17268689 DOI: 10.1039/b615596k] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Fluctuations in the fluorescence polarization degree and direction are reported for the first time for single conjugated polymer molecules embedded in a polystyrene matrix at room temperature. The polymer molecule, a polythiophene derivative, clearly emits as a multi-chromophore ensemble showing that the energy does not funnel to any specific low-energy trap. The fluorescence instead originates from thermally populated exciton states with different relative orientations of the transition dipole moments. The fluctuations in the fluorescence polarization are explained in terms of changes in the relative contributions of the different exciton states to the signal due to conformational fluctuations of the molecule or selective exciton quenching by triplet states.
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Affiliation(s)
- M Forster
- Department of Chemical Physics, Lund University, Box 124, 22100, Lund, Sweden
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30
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Hania PR, Thomsson D, Scheblykin IG. Host Matrix Dependent Fluorescence Intensity Modulation by an Electric Field in Single Conjugated Polymer Chains. J Phys Chem B 2006; 110:25895-900. [PMID: 17181237 DOI: 10.1021/jp0653252] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
An electric field oscillating at a frequency approximately 1 Hz is found to induce strong modulation of the fluorescence intensity of single poly[2-methoxy,5-(2'-ethyl-hexyloxy)-p-phenylene vinylene] (MEH-PPV) molecules (MW approximately 10(6)) embedded in a poly(methyl methacrylate) (PMMA) matrix. The MEH-PPV polymer chains are carefully isolated from the electrodes to avoid effects of injection. In a polystyrene matrix, fluorescence intensity modulations are on average much less pronounced. The difference in average modulation depth can be explained in terms of lower field-induced exciton dissociation rates in the MEH-PPV/polystyrene system compared to MEH-PPV/PMMA because of a lack of suitable acceptor sites. The observed electric field dependence of single-molecule fluorescence strongly suggests that energy transfer from singlet or even triplet excitons to long-living on-chain hole polarons contributes to the observed modulations. The observed large qualitative differences between the responses of different molecules probably reflect differences in chain topology and strongly anisotropic distributions of acceptor sites, while the hysteretic response of some molecules indicates conformational switching.
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Affiliation(s)
- P Ralph Hania
- Department of Chemical Physics, University of Lund, Box 124, SE-22100 Sweden
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31
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Grey JK, Kim DY, Norris BC, Miller WL, Barbara PF. Size-Dependent Spectroscopic Properties of Conjugated Polymer Nanoparticles. J Phys Chem B 2006; 110:25568-72. [PMID: 17181186 DOI: 10.1021/jp065990a] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
This paper is focused on how the spectroscopic properties of conjugated polymers evolve in the size range between single polymer chains and the bulk material. The measurements used single-particle spectroscopy techniques and include both static and dynamic measurements. The main observation of this work is that the spectroscopic properties of MEH-PPV evolve rapidly as a function of nanoparticle size and achieve bulk-like properties for nanoparticles greater than 10 nm in size. Nanoparticles were assembled by a reprecipitation technique and characterized by fluorescence emission spectroscopy. The physical origin of the size-dependent spectroscopic properties is assigned to the distance dependence of four main processes: electronic energy transfer between blue and red sites, triplet-triplet annihilation, singlet exciton quenching by triplets, and singlet exciton quenching by hole polarons.
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Affiliation(s)
- John K Grey
- Center for Nano- and Molecular Science and Technology and Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712, USA
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32
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Mirzov O, Scheblykin IG. Photoluminescence spectra of a conjugated polymer: from films and solutions to single molecules. Phys Chem Chem Phys 2006; 8:5569-76. [PMID: 17136272 DOI: 10.1039/b612073c] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The purpose of this work is to address the issue of applicability of single-molecule spectroscopy (SMS) results for conjugated polymers to "bulk" samples, e.g. conjugated polymer films. Also, some apparent inconsistencies in the literature on SMS regarding the photoluminescence spectral position of conjugated polymers are discussed. We present a series of photoluminescence spectra of thin films of the conjugated polymer poly(2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene-vinylene) (MEH-PPV) with a wide range of varying thickness. The thickness was varied from approximately 20 nm to the value corresponding to well-separated single molecules (SMS sample). The thickness variation resulted in a strong ( approximately 2000 cm(-1)) blue-shift and broadening of the spectrum. The result was reproduced on isolated molecules embedded into a PMMA matrix. This effect cannot be explained by a decrease in energy transfer "freedom" alone. We performed a comprehensive comparison of presented and elsewhere published spectra of MEH-PPV polymer and oligomers in different samples: films, solutions, isolated-molecule coatings and standard SMS samples. The comparison allows that the main reason behind the blue shift is conformational disorder, which is largely dependent on the sample. We also discuss some experimental aspects of SMS, such as representativeness of detected molecules, spectral sensitivity of a setup and temperature. Together with differences in sample preparation method, these issues can explain the existing inconsistencies in the literature.
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Affiliation(s)
- O Mirzov
- Chemical Physics, Lund University, P.O. Box 124, 22100 Lund, Sweden
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Lee YJ, Kim DY, Barbara PF. Effect of Sample Preparation and Excitation Conditions on the Single Molecule Spectroscopy of Conjugated Polymers. J Phys Chem B 2006; 110:9739-42. [PMID: 16706417 DOI: 10.1021/jp056727x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Extensive new single molecule spectroscopy (SMS) data on the conjugated polymer MEH-PPV at low temperature were obtained. In particular, the combined effects of sample preparation and excitation condition were explored in detail. The data confirm previous observations from this laboratory that (i) the distribution of emission maxima of single MEH-PPV molecules has a bimodal distribution and (ii) the single molecule emission spectrum of MEH-PPV exhibits few time-dependent fluctuations of the emission intensity, band shape, or spectral maxima. These data also help explain the discrepancy among the various published SMS data on this compound and suggest that environmental impurities, long irradiation times, nearby interfaces, and incomplete data sampling may account for some of the discrepancies among the published data.
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Affiliation(s)
- Young Jong Lee
- Center for Nano- and Molecular Science and Technology and Department of Chemistry and Biochemistry, University of Texas at Austin, 78712, USA
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Becker K, Lupton JM. Efficient Light Harvesting in Dye-Endcapped Conjugated Polymers Probed by Single Molecule Spectroscopy. J Am Chem Soc 2006; 128:6468-79. [PMID: 16683812 DOI: 10.1021/ja0609405] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The development of sophisticated microscopic models of energy transfer in linear multichromophoric systems such as conjugated polymers is rarely matched by suitable experimental studies on the microscopic level. To assess the roles of structural, temporal, and energetic disorder in energy transfer, single molecule spectroscopic investigations of the elementary processes leading to energetic relaxation in conjugated polymers are desirable. We present a detailed study of energy transfer processes occurring in dye-endcapped conjugated polymer molecules on the single molecule level. These processes are mostly masked in ensemble investigations. Highly efficient intramolecular energy transfer along a single polyindenofluorene chain to a perylene endcap occurs in many instances and is resolved in real time. We further consider the spectral emission characteristics of the single molecule, the polarization anisotropy which reveals the chain conformation, the fluorescence intermittency, and the temperature dependence and conclude that the efficiency of energy transfer in the ensemble is controlled by the statistics of the individual molecules. The weak thermal activation of energy transfer indicates the involvement of vibrational modes in interchromophoric coupling. Whereas backbone-endcap coupling is strong, the rate-limiting step for intramolecular energy transfer is the migration along the backbone. The results are particularly relevant to understanding undesired exciton trapping on fluorenone defects in polyfluorenes.
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Affiliation(s)
- Klaus Becker
- Photonics and Optoelectronics Group, Physics Department and CeNS, Ludwig-Maximilians-Universität, Amalienstrasse 54, 80799 München, Germany
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36
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Schindler F, Lupton JM, Müller J, Feldmann J, Scherf U. How single conjugated polymer molecules respond to electric fields. NATURE MATERIALS 2006; 5:141-6. [PMID: 16400331 DOI: 10.1038/nmat1549] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2005] [Accepted: 11/10/2005] [Indexed: 05/06/2023]
Abstract
Conjugated polymers find applications in a range of devices such as light-emitting diodes, field-effect transistors and solar cells. The elementary electronic response of these semiconductors to electric fields is understood in terms of nanoscale perturbations of charge density. We demonstrate a general breaking of spatial charge symmetry by considering the linear Stark effect in the emission of single chromophores on individual chains. Spectral shifts of several nanometres occur due to effective dipoles exceeding 10 D. Although the electric field does not ionize the exciton, some molecules exhibit field-induced intensity modulations. This quenching illustrates the equivalence of charge symmetry breaking and polaron-pair or charge-transfer-state formation, and provides a microscopic picture of permanent charging, which leads to doping and exciton dissociation in actual devices. In addition to using this tuneable emission in single-photon electro-optic modulators, hysteresis in the Stark shift suggests a route to designing nanoscale memory elements such as molecular switches.
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Affiliation(s)
- Florian Schindler
- Photonics and Optoelectronics Group, Physics Department and Center for NanoScience, Ludwig-Maximilians-Universität, Amalienstrasse 54, 80799 Munich, Germany
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