1
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Lin LC, Dill RD, Thorley KJ, Parkin SR, Anthony JE, Johnson JC, Damrauer NH. Revealing the Singlet Fission Mechanism for a Silane-Bridged Thienotetracene Dimer. J Phys Chem A 2024; 128:3982-3992. [PMID: 38717589 PMCID: PMC11129308 DOI: 10.1021/acs.jpca.4c01463] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2024] [Revised: 04/25/2024] [Accepted: 04/26/2024] [Indexed: 05/24/2024]
Abstract
Tetraceno[2,3-b]thiophene is regarded as a strong candidate for singlet fission-based solar cell applications due to its mixed characteristics of tetracene and pentacene that balance exothermicity and triplet energy. An electronically weakly coupled tetraceno[2,3-b]thiophene dimer (Et2Si(TIPSTT)2) with a single silicon atom bridge has been synthesized, providing a new platform to investigate the singlet fission mechanism involving the two acene chromophores. We study the excited state dynamics of Et2Si(TIPSTT)2 by monitoring the evolution of multiexciton coupled triplet states, 1TT to 5TT to 3TT to T1 + S0, upon photoexcitation with transient absorption, temperature-dependent transient absorption, and transient/pulsed electron paramagnetic resonance spectroscopies. We find that the photoexcited singlet lifetime is 107 ps, with 90% evolving to form the TT state, and the complicated evolution between the multiexciton states is unraveled, which can be an important reference for future efforts toward tetraceno[2,3-b]thiophene-based singlet fission solar cells.
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Affiliation(s)
- Liang-Chun Lin
- Department
of Chemistry, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Ryan D. Dill
- Department
of Chemistry, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Karl J. Thorley
- Department
of Chemistry & Center for Applied Energy Research, University of Kentucky, Lexington, Kentucky 40506-0055, United States
| | - Sean R. Parkin
- Department
of Chemistry & Center for Applied Energy Research, University of Kentucky, Lexington, Kentucky 40506-0055, United States
| | - John E. Anthony
- Department
of Chemistry & Center for Applied Energy Research, University of Kentucky, Lexington, Kentucky 40506-0055, United States
| | - Justin C. Johnson
- National
Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States
- Renewable
and Sustainable Energy Institute (RASEI), University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Niels H. Damrauer
- Department
of Chemistry, University of Colorado Boulder, Boulder, Colorado 80309, United States
- Renewable
and Sustainable Energy Institute (RASEI), University of Colorado Boulder, Boulder, Colorado 80309, United States
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2
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Hou Y, Papadopoulos I, Bo Y, Wollny AS, Ferguson MJ, Mai LA, Tykwinski RR, Guldi DM. Catalyzing Singlet Fission by Transition Metals: Second versus Third Row Effects. PRECISION CHEMISTRY 2023; 1:555-564. [PMID: 38037593 PMCID: PMC10685717 DOI: 10.1021/prechem.3c00082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/20/2023] [Revised: 10/02/2023] [Accepted: 10/04/2023] [Indexed: 12/02/2023]
Abstract
The synthesis and characterization of platinum(II) and palladium(II) complexes bearing two (dimers Pt(Lpc)2Cl2 and Pd(Lpc)2Cl2), one (monomers Pt(Lpc)(Lref)Cl2 and Pd(Lpc)(Lref)Cl2), or no (reference compounds Pt(Lref)2Cl2 and Pd(Lref)2Cl2) pentacene-based pyridyl ligands are presented. Photophysical properties of the dimers are probed by means of steady-state and time-resolved transient absorption measurements in comparison to the monomer and model compounds. Our results document that despite enhanced spin-orbit coupling from the presence of heavy atoms, intramolecular singlet fission (iSF) is not challenged by intersystem crossing. iSF thus yields correlated triplet pairs and even uncorrelated triplet excited states upon decoherence. Importantly, significant separation of the two pentacenyl groups facilitates decoupling of the two chromophores. Furthermore, the mechanism of iSF is altered depending on the respective metal center, that is, Pt(II) versus Pd(II). The dimer based on Pt(II), Pt(Lpc)2Cl2, exhibits a direct pathway for the iSF and forms a correlated triplet pair with singlet-quintet spin-mixing within 10 ns in variable solvents. On the other hand, the dimer based on Pd(II), Pd(Lpc)2Cl2, leads to charge transfer mixing during the population of the correlated triplet pair that is dependent on solvent polarity. Moreover, Pd(Lpc)2Cl2 gives rise to a stable equilibrium between singlet and quintet correlated triplet pairs with lifetimes of up to 170 ns. Inherent differences in the size and polarizability, when contrasting platinum(II) with palladium(II), are the most likely rationale for the underlying trends.
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Affiliation(s)
- Yuxuan Hou
- Department
of Chemistry, University of Alberta, 11227 Saskatchewan Drive, Edmonton, Alberta T6G 2G2, Canada
| | - Ilias Papadopoulos
- Department
of Chemistry and Pharmacy & Interdisciplinary Center for Molecular
Materials (ICMM), Friedrich-Alexander-University
Erlangen-Nuremberg, Egerlandstraße 3, 91058 Erlangen, Germany
| | - Yifan Bo
- Department
of Chemistry and Pharmacy & Interdisciplinary Center for Molecular
Materials (ICMM), Friedrich-Alexander-University
Erlangen-Nuremberg, Egerlandstraße 3, 91058 Erlangen, Germany
| | - Anna-Sophie Wollny
- Department
of Chemistry and Pharmacy & Interdisciplinary Center for Molecular
Materials (ICMM), Friedrich-Alexander-University
Erlangen-Nuremberg, Egerlandstraße 3, 91058 Erlangen, Germany
| | - Michael J. Ferguson
- Department
of Chemistry, University of Alberta, 11227 Saskatchewan Drive, Edmonton, Alberta T6G 2G2, Canada
| | - Lukas A. Mai
- Department
of Chemistry and Pharmacy & Interdisciplinary Center for Molecular
Materials (ICMM), Friedrich-Alexander-University
Erlangen-Nuremberg, Egerlandstraße 3, 91058 Erlangen, Germany
| | - Rik R. Tykwinski
- Department
of Chemistry, University of Alberta, 11227 Saskatchewan Drive, Edmonton, Alberta T6G 2G2, Canada
| | - Dirk M. Guldi
- Department
of Chemistry and Pharmacy & Interdisciplinary Center for Molecular
Materials (ICMM), Friedrich-Alexander-University
Erlangen-Nuremberg, Egerlandstraße 3, 91058 Erlangen, Germany
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3
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He G, Parenti KR, Budden PJ, Niklas J, Macdonald T, Kumarasamy E, Chen X, Yin X, McCamey DR, Poluektov OG, Campos LM, Sfeir MY. Unraveling Triplet Formation Mechanisms in Acenothiophene Chromophores. J Am Chem Soc 2023; 145:22058-22068. [PMID: 37787467 DOI: 10.1021/jacs.3c07082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/04/2023]
Abstract
The evolution of molecular platforms for singlet fission (SF) chromophores has fueled the quest for new compounds capable of generating triplets quantitatively at fast time scales. As the exploration of molecular motifs for SF has diversified, a key challenge has emerged in identifying when the criteria for SF have been satisfied. Here, we show how covalently bound molecular dimers uniquely provide a set of characteristic optical markers that can be used to distinguish triplet pair formation from processes that generate an individual triplet. These markers are contained within (i) triplet charge-transfer excited state absorption features, (ii) kinetic signatures of triplet-triplet annihilation processes, and (iii) the modulation of triplet formation rates using bridging moieties between chromophores. Our assignments are verified by time-resolved electron paramagnetic resonance (EPR) measurements, which directly identify triplet pairs by their electron spin and polarization patterns. We apply these diagnostic criteria to dimers of acenothiophene derivatives in solution that were recently reported to undergo efficient intermolecular SF in condensed media. While the electronic structure of these heteroatom-containing chromophores can be broadly tuned, the effect of their enhanced spin-orbit coupling and low-energy nonbonding orbitals on their SF dynamics has not been fully determined. We find that SF is fast and efficient in tetracenothiophene but that anthradithiophene exhibits fast intersystem crossing due to modifications of the singlet and triplet excited state energies upon functionalization of the heterocycle. We conclude that it is not sufficient to assign SF based on comparisons of the triplet formation kinetics between monomer and multichromophore systems.
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Affiliation(s)
- Guiying He
- Department of Physics, Graduate Center, City University of New York, New York, New York 10016, United States
- Photonics Initiative, Advanced Science Research Center, City University of New York, New York, New York 10031, United States
| | - Kaia R Parenti
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Peter J Budden
- Department of Physics, Graduate Center, City University of New York, New York, New York 10016, United States
- Photonics Initiative, Advanced Science Research Center, City University of New York, New York, New York 10031, United States
| | - Jens Niklas
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Thomas Macdonald
- ARC Centre of Excellence in Exciton Science, School of Physics, UNSW Sydney, Sydney, 2052 NSW, Australia
| | - Elango Kumarasamy
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Xing Chen
- Key Laboratory of Cluster Science, Ministry of Education of China, Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 102488, P. R. China
| | - Xiaodong Yin
- Key Laboratory of Cluster Science, Ministry of Education of China, Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 102488, P. R. China
| | - Dane R McCamey
- ARC Centre of Excellence in Exciton Science, School of Physics, UNSW Sydney, Sydney, 2052 NSW, Australia
| | - Oleg G Poluektov
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Luis M Campos
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Matthew Y Sfeir
- Department of Physics, Graduate Center, City University of New York, New York, New York 10016, United States
- Photonics Initiative, Advanced Science Research Center, City University of New York, New York, New York 10031, United States
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4
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Sutherland GA, Pidgeon JP, Lee HKH, Proctor MS, Hitchcock A, Wang S, Chekulaev D, Tsoi WC, Johnson MP, Hunter CN, Clark J. Twisted Carotenoids Do Not Support Efficient Intramolecular Singlet Fission in the Orange Carotenoid Protein. J Phys Chem Lett 2023:6135-6142. [PMID: 37364284 DOI: 10.1021/acs.jpclett.3c01139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/28/2023]
Abstract
Singlet exciton fission is the spin-allowed generation of two triplet electronic excited states from a singlet state. Intramolecular singlet fission has been suggested to occur on individual carotenoid molecules within protein complexes provided that the conjugated backbone is twisted out of plane. However, this hypothesis has been forwarded only in protein complexes containing multiple carotenoids and bacteriochlorophylls in close contact. To test the hypothesis on twisted carotenoids in a "minimal" one-carotenoid system, we study the orange carotenoid protein (OCP). OCP exists in two forms: in its orange form (OCPo), the single bound carotenoid is twisted, whereas in its red form (OCPr), the carotenoid is planar. To enable room-temperature spectroscopy on canthaxanthin-binding OCPo and OCPr without laser-induced photoconversion, we trap them in a trehalose glass. Using transient absorption spectroscopy, we show that there is no evidence of long-lived triplet generation through intramolecular singlet fission despite the canthaxanthin twist in OCPo.
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Affiliation(s)
- George A Sutherland
- Plants, Photosynthesis and Soil, School of Biosciences, University of Sheffield, Sheffield S10 2TN, U.K
| | - James P Pidgeon
- Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, U.K
| | - Harrison Ka Hin Lee
- SPECIFIC, Faculty of Science and Engineering, Swansea University, Swansea SA1 8EN, U.K
| | - Matthew S Proctor
- Plants, Photosynthesis and Soil, School of Biosciences, University of Sheffield, Sheffield S10 2TN, U.K
| | - Andrew Hitchcock
- Plants, Photosynthesis and Soil, School of Biosciences, University of Sheffield, Sheffield S10 2TN, U.K
| | - Shuangqing Wang
- Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, U.K
| | - Dimitri Chekulaev
- Department of Chemistry, University of Sheffield, Sheffield S3 7HF, U.K
| | - Wing Chung Tsoi
- SPECIFIC, Faculty of Science and Engineering, Swansea University, Swansea SA1 8EN, U.K
| | - Matthew P Johnson
- Plants, Photosynthesis and Soil, School of Biosciences, University of Sheffield, Sheffield S10 2TN, U.K
| | - C Neil Hunter
- Plants, Photosynthesis and Soil, School of Biosciences, University of Sheffield, Sheffield S10 2TN, U.K
| | - Jenny Clark
- Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, U.K
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5
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Quantum interference effects elucidate triplet-pair formation dynamics in intramolecular singlet-fission molecules. Nat Chem 2023; 15:339-346. [PMID: 36585444 DOI: 10.1038/s41557-022-01107-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Accepted: 11/03/2022] [Indexed: 12/31/2022]
Abstract
Quantum interference (QI)-the constructive or destructive interference of conduction pathways through molecular orbitals-plays a fundamental role in enhancing or suppressing charge and spin transport in organic molecular electronics. Graphical models were developed to predict constructive versus destructive interference in polyaromatic hydrocarbons and have successfully estimated the large conductivity differences observed in single-molecule transport measurements. A major challenge lies in extending these models to excitonic (photoexcited) processes, which typically involve distinct orbitals with different symmetries. Here we investigate how QI models can be applied as bridging moieties in intramolecular singlet-fission compounds to predict relative rates of triplet pair formation. In a series of bridged intramolecular singlet-fission dimers, we found that destructive QI always leads to a slower triplet pair formation across different bridge lengths and geometries. A combined experimental and theoretical approach reveals the critical considerations of bridge topology and frontier molecular orbital energies in applying QI conductance principles to predict rates of multiexciton generation.
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6
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Shi Y, Bao XY. QSPR Modeling for the Prediction of the Triplet Yield of Singlet Fission Materials. JOURNAL OF SAUDI CHEMICAL SOCIETY 2023. [DOI: 10.1016/j.jscs.2023.101614] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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7
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Influence of core-twisted structure on singlet fission in perylenediimide film. J Photochem Photobiol A Chem 2022. [DOI: 10.1016/j.jphotochem.2022.114473] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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8
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He G, Parenti KR, Campos LM, Sfeir MY. Direct Exciton Harvesting from a Bound Triplet Pair. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2203974. [PMID: 35973675 DOI: 10.1002/adma.202203974] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Revised: 07/11/2022] [Indexed: 06/15/2023]
Abstract
Singlet fission is commonly defined as the generation of two triplet excitons from a single absorbed photon. However, ambiguities within this definition arise due to the complexity of the various double triplet states that exist in SF chromophores and the corresponding interconversion processes. To clarify this process, singlet fission is frequently depicted as sequential two-step conversion in which a singlet exciton decays into a bound triplet-pair biexciton state that dissociates into two "free" triplet excitons. However, this model discounts the potential for direct harvesting from the coupled biexciton state. Here, it is demonstrated that individual triplet excitons can be extracted directly from a bound triplet pair. It is demonstrated that due to the requirement for geminate triplet-triplet annihilation in intramolecular singlet fission compounds, unique spectral and kinetic signatures can be used to quantify triplet-pair harvesting yields. An internal quantum efficiency for triplet exciton transfer from the triplet pair of >50%, limited only by the solubility of the compounds is achieved. The harvesting process is not dependent on the net multiplicity of the triplet-pair state, suggesting that an explicit, independent dissociation step is not a requirement for using triplet pairs to do chemical or electrical work.
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Affiliation(s)
- Guiying He
- Department of Physics, Graduate Center, City University of New York, New York, NY, 10016, USA
- Photonics Initiative, Advanced Science Research Center, City University of New York, New York, NY, 10031, USA
| | - Kaia R Parenti
- Department of Chemistry, Columbia University, New York, NY, 10027, USA
| | - Luis M Campos
- Department of Chemistry, Columbia University, New York, NY, 10027, USA
| | - Matthew Y Sfeir
- Department of Physics, Graduate Center, City University of New York, New York, NY, 10016, USA
- Photonics Initiative, Advanced Science Research Center, City University of New York, New York, NY, 10031, USA
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9
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Pensack RD, Purdum GE, Mazza SM, Grieco C, Asbury JB, Anthony JE, Loo YL, Scholes GD. Excited-State Dynamics of 5,14- vs 6,13-Bis(trialkylsilylethynyl)-Substituted Pentacenes: Implications for Singlet Fission. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2022; 126:9784-9793. [PMID: 35756579 PMCID: PMC9210346 DOI: 10.1021/acs.jpcc.2c00897] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2022] [Revised: 05/20/2022] [Indexed: 05/16/2023]
Abstract
Singlet fission is a process in conjugated organic materials that has the potential to considerably improve the performance of devices in many applications, including solar energy conversion. In any application involving singlet fission, efficient triplet harvesting is essential. At present, not much is known about molecular packing arrangements detrimental to singlet fission. In this work, we report a molecular packing arrangement in crystalline films of 5,14-bis(triisopropylsilylethynyl)-substituted pentacene, specifically a local (pairwise) packing arrangement, responsible for complete quenching of triplet pairs generated via singlet fission. We first demonstrate that the energetic condition necessary for singlet fission is satisfied in amorphous films of the 5,14-substituted pentacene derivative. However, while triplet pairs form highly efficiently in the amorphous films, only a modest yield of independent triplets is observed. In crystalline films, triplet pairs also form highly efficiently, although independent triplets are not observed because triplet pairs decay rapidly and are quenched completely. We assign the quenching to a rapid nonadiabatic transition directly to the ground state. Detrimental quenching is observed in crystalline films of two additional 5,14-bis(trialkylsilylethynyl)-substituted pentacenes with either ethyl or isobutyl substituents. Developing a better understanding of the losses identified in this work, and associated molecular packing, may benefit overcoming losses in solids of other singlet fission materials.
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Affiliation(s)
- Ryan D. Pensack
- Department
of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Geoffrey E. Purdum
- Department
of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | - Samuel M. Mazza
- Department
of Chemistry, University of Kentucky, Lexington, Kentucky 40506, United States
| | - Christopher Grieco
- Department
of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - John B. Asbury
- Department
of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - John E. Anthony
- Department
of Chemistry, University of Kentucky, Lexington, Kentucky 40506, United States
| | - Yueh-Lin Loo
- Department
of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States
- Andlinger
Center for Energy and the Environment, Princeton
University, Princeton, New Jersey 08544, United States
| | - Gregory D. Scholes
- Department
of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
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10
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Fumanal M, Corminboeuf C. Optimizing the Thermodynamics and Kinetics of the Triplet-Pair Dissociation in Donor-Acceptor Copolymers for Intramolecular Singlet Fission. CHEMISTRY OF MATERIALS : A PUBLICATION OF THE AMERICAN CHEMICAL SOCIETY 2022; 34:4115-4121. [PMID: 35573105 PMCID: PMC9097278 DOI: 10.1021/acs.chemmater.2c00367] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Revised: 03/09/2022] [Indexed: 06/15/2023]
Abstract
Singlet fission (SF) is a two-step process in which a singlet splits into two triplets throughout the so-called correlated triplet-pair (1TT) state. Intramolecular SF (iSF) materials, in particular, have attracted growing interest as they can be easily implemented in single-junction solar cells and boost their power conversion efficiency. Still, the potential of iSF materials such as polymers and oligomers for photovoltaic applications has been partially hindered by their ability to go beyond the 1TT intermediate and generate free triplets, whose mechanism remains poorly understood. In this work, the main aspects governing the 1TT dissociation in donor-acceptor copolymers and the key features that optimize this process are exposed. First, we show that both thermodynamics and kinetics play a crucial role in the intramolecular triplet-pair separation and second, we uncover the inherent flexibility of the donor unit as the fundamental ingredient to optimize them simultaneously. Overall, these results provide a better understanding of the intramolecular 1TT dissociation process and establish a new paradigm for the development of novel iSF active materials.
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Affiliation(s)
- Maria Fumanal
- Laboratory for Computational Molecular
Design, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne
(EPFL), CH-1015 Lausanne, Switzerland
| | - Clémence Corminboeuf
- Laboratory for Computational Molecular
Design, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne
(EPFL), CH-1015 Lausanne, Switzerland
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11
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Ringström R, Edhborg F, Schroeder ZW, Chen L, Ferguson MJ, Tykwinski RR, Albinsson B. Molecular rotational conformation controls the rate of singlet fission and triplet decay in pentacene dimers. Chem Sci 2022; 13:4944-4954. [PMID: 35655894 PMCID: PMC9067590 DOI: 10.1039/d1sc06285a] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Accepted: 04/03/2022] [Indexed: 12/02/2022] Open
Abstract
Three pentacene dimers have been synthesized to investigate the effect of molecular rotation and rotational conformations on singlet fission (SF). In all three dimers, the pentacene units are linked by a 1,4-diethynylphenylene spacer that provides almost unimpeded rotational freedom between the pentacene- and phenylene-subunits in the parent dimer. Substituents on the phenylene spacer add varying degrees of steric hindrance that restricts both the rotation and the equilibrium distribution of different conformers; the less restricted conformers exhibit faster SF and more rapid subsequent triplet-pair recombination. Furthermore, the rotational conformers have small shifts in their absorption spectra and this feature has been used to selectively excite different conformers and study the resulting SF. Femtosecond transient absorption studies at 100 K reveal that the same dimer can have orders of magnitude faster SF in a strongly coupled conformer compared to a more weakly coupled one. Measurements in polystyrene further show that the SF rate is nearly independent of viscosity whereas the triplet pair lifetime is considerably longer in a high viscosity medium. The results provide insight into design criteria for maintaining high initial SF rate while suppressing triplet recombination in intramolecular singlet fission.
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Affiliation(s)
- Rasmus Ringström
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology Kemigården 4 SE-412 96 Göteborg Sweden
| | - Fredrik Edhborg
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology Kemigården 4 SE-412 96 Göteborg Sweden
| | - Zachary W Schroeder
- Department of Chemistry, University of Alberta Edmonton Alberta T6G 2G2 Canada
| | - Lan Chen
- Department of Chemistry, University of Alberta Edmonton Alberta T6G 2G2 Canada
| | - Michael J Ferguson
- Department of Chemistry, University of Alberta Edmonton Alberta T6G 2G2 Canada
| | - Rik R Tykwinski
- Department of Chemistry, University of Alberta Edmonton Alberta T6G 2G2 Canada
| | - Bo Albinsson
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology Kemigården 4 SE-412 96 Göteborg Sweden
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12
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Miyazaki K, Ananth N. Singularity-free internal conversion golden-rule rate with application to correlated triplet pair recombination in bipentacenes. J Chem Phys 2022; 156:044111. [DOI: 10.1063/5.0076717] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Ken Miyazaki
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA
| | - Nandini Ananth
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA
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