1
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Vong D, Maleki F, Novak EC, Daemen LL, Moulé AJ. Measuring Intermolecular Excited State Geometry for Favorable Singlet Fission in Tetracene. J Phys Chem Lett 2024; 15:1188-1194. [PMID: 38270396 DOI: 10.1021/acs.jpclett.3c02343] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2024]
Abstract
Singlet fission (SF) is the process of converting an excited singlet to a pair of excited triplets. Harvesting two charges from a single photon has the potential to increase photovoltaic device efficiencies. Acenes, such as tetracene and pentacene, are model molecules for studying SF. Despite SF being an endoergic process for tetracene and exoergic for pentacene, both acenes exhibit near unity SF quantum efficiencies, raising questions about how tetracene can overcome the energy barrier. Here, we use recently developed instrumentation to measure inelastic neutron scattering (INS) while optically exciting the model molecules using two different excitation energies. The spectroscopic results reveal intermolecular structural relaxation due to the presence of a triplet excited state. The structural dynamics of the combined excited state molecule and surrounding tetracene molecules are further studied using time-dependent density functional theory (TD-DFT), which shows that the singlet and triplet levels shift due to the excited state geometry, reducing the uphill energy barrier for SF to within kT.
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Affiliation(s)
- Daniel Vong
- Department of Materials Science and Engineering, University of California Davis, Davis, California 95616, United States
| | - Farahnaz Maleki
- Department of Chemical Engineering, University of California Davis, Davis, California 95616, United States
| | - Eric C Novak
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, United States
| | - Luke L Daemen
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, United States
| | - Adam J Moulé
- Department of Chemical Engineering, University of California Davis, Davis, California 95616, United States
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2
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Unger F, Lepple D, Asbach M, Craciunescu L, Zeiser C, Kandolf AF, Fišer Z, Hagara J, Hagenlocher J, Hiller S, Haug S, Deutsch M, Grüninger P, Novák J, Bettinger HF, Broch K, Engels B, Schreiber F. Optical Absorption Properties in Pentacene/Tetracene Solid Solutions. J Phys Chem A 2024; 128:747-760. [PMID: 38232326 DOI: 10.1021/acs.jpca.3c06737] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2024]
Abstract
Modifying the optical and electronic properties of crystalline organic thin films is of great interest for improving the performance of modern organic semiconductor devices. Therein, the statistical mixing of molecules to form a solid solution provides an opportunity to fine-tune optical and electronic properties. Unfortunately, the diversity of intermolecular interactions renders mixed organic crystals highly complex, and a holistic picture is still lacking. Here, we report a study of the optical absorption properties in solid solutions of pentacene and tetracene, two prototypical organic semiconductors. In the mixtures, the optical properties can be continuously modified by statistical mixing at the molecular level. Comparison with time-dependent density functional theory calculations on occupationally disordered clusters unravels the electronic origin of the low energy optical transitions. The disorder partially relaxes the selection rules, leading to additional optical transitions that manifest as optical broadening. Furthermore, the contribution of diabatic charge-transfer states is modified in the mixtures, reducing the observed splitting in the 0-0 vibronic transition. Additional comparisons with other blended systems generalize our results and indicate that changes in the polarizability of the molecular environment in organic thin-film blends induce shifts in the absorption spectrum.
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Affiliation(s)
- Frederik Unger
- Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
| | - Daniel Lepple
- Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
| | - Maximilian Asbach
- Julius-Maximilian University Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Luca Craciunescu
- Julius-Maximilian University Würzburg, Am Hubland, 97074 Würzburg, Germany
- Institute of Chemical Sciences, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh, EH14 4AS Scotland, U.K
| | - Clemens Zeiser
- Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
| | - Andreas F Kandolf
- Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
- Institute of Organic Chemistry, University of Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany
| | - Zbyněk Fišer
- Department of Condensed Matter Physics (UFKL), Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic
| | - Jakub Hagara
- Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
| | - Jan Hagenlocher
- Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
| | - Stefan Hiller
- Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
| | - Sara Haug
- Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
| | - Marian Deutsch
- Julius-Maximilian University Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Peter Grüninger
- Institute of Organic Chemistry, University of Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany
| | - Jiří Novák
- Department of Condensed Matter Physics (UFKL), Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic
| | - Holger F Bettinger
- Institute of Organic Chemistry, University of Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany
| | - Katharina Broch
- Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
| | - Bernd Engels
- Julius-Maximilian University Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Frank Schreiber
- Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
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3
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Bhattacharyya A, Sahu A, Patra S, Tiwari V. Low- and high-frequency vibrations synergistically enhance singlet exciton fission through robust vibronic resonances. Proc Natl Acad Sci U S A 2023; 120:e2310124120. [PMID: 38019862 PMCID: PMC10710028 DOI: 10.1073/pnas.2310124120] [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: 06/19/2023] [Accepted: 10/14/2023] [Indexed: 12/01/2023] Open
Abstract
Singlet exciton fission (SEF) is initiated by ultrafast internal conversion of a singlet exciton into a correlated triplet pair [Formula: see text]. The "reaction coordinates" for ultrafast SEF even in archetypal systems such as pentacene thin film remain unclear. Couplings between fast electrons and slow nuclei are ubiquitous across a range of phenomena in chemistry. Accordingly, spectroscopic detection of vibrational coherences in the [Formula: see text] photoproduct motivated investigations into a possible role of vibronic coupling, akin to that reported in several photosynthetic proteins. However, acenes are very different from chlorophylls with 10× larger vibrational displacements upon photoexcitation and low-frequency vibrations modulating intermolecular orbital overlaps. Whether (and if so how) these unique features carry any mechanistic significance for SEF remains a poorly understood question. Accordingly, synthetic design of new molecules aiming to mimic this process across the solar spectrum has broadly relied on tuning electronic couplings. We address this gap and identify previously unrecognized synergistic interplay of vibrations, which in striking contrast to photosynthesis, vitally enhances SEF across a broad, nonselective and, therefore, unavoidable range of vibrational frequencies. We argue that attaching mechanistic significance to spectroscopically observed prominent quantum beats is misleading. Instead, we show that vibronic mixing leads to anisotropic quantum beats and propose readily implementable polarization-based two-dimensional electronic spectroscopy experiments which uniquely distinguish vibrations which drive vibronic mixing and promote SEF, against spectator vibrations simply accompanying ultrafast internal conversion. Our findings introduce crucial ingredients in synthetic design of SEF materials and spectroscopy experiments aiming to decipher mechanistic details from quantum beats.
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Affiliation(s)
- Atandrita Bhattacharyya
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore560012, India
| | - Amitav Sahu
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore560012, India
| | - Sanjoy Patra
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore560012, India
| | - Vivek Tiwari
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore560012, India
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4
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CRUZ CD, STEPHENSON JC, ENGMANN S, BITTLE EG, WAHLSTRAND JK. Pump-probe phase spectroscopy with submilliradian sensitivity and nanosecond time delay using Michelson interferometers. OPTICS EXPRESS 2023; 31:14299-14307. [PMID: 37157297 PMCID: PMC11258875 DOI: 10.1364/oe.483358] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Accepted: 02/15/2023] [Indexed: 05/10/2023]
Abstract
Using two Michelson interferometers, we describe an experimental scheme for sensitive pump-probe spectral interferometry measurements at long time delays. It has practical advantages over the Sagnac interferometer method typically used when long-time delays are required. First, with the Sagnac interferometer, achieving many nanosecond delays requires expanding the size of the interferometer so that the reference pulse arrives before the probe pulse. Because the two pulses still pass through the same region of the sample, long-lived effects can still affect the measurement. In our scheme, the probe and reference pulses are spatially separated at the sample, alleviating the need for a large interferometer. Second, in our scheme, a fixed delay between probe and reference pulses is straightforward to produce and is continuously adjustable while maintaining alignment. Two applications are demonstrated. First, transient phase spectra are presented in a thin tetracene film with up to 5 ns probe delay. Second, impulsive stimulated Raman measurements are presented in Bi4Ge3O12. The signal-to-noise using the double Michelson technique is comparable to previously described methods with the added advantage of arbitrarily long pump-probe time delays.
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Affiliation(s)
- C. D. CRUZ
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
| | - J. C. STEPHENSON
- Associate, Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
| | - S. ENGMANN
- Associate, Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
- Theiss Research, La Jolla, CA 92037, USA
| | - E. G. BITTLE
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
| | - J. K. WAHLSTRAND
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
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5
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Andrusenko I, Hall CL, Mugnaioli E, Potticary J, Hall SR, Schmidt W, Gao S, Zhao K, Marom N, Gemmi M. True molecular conformation and structure determination by three-dimensional electron diffraction of PAH by-products potentially useful for electronic applications. IUCRJ 2023; 10:131-142. [PMID: 36598508 PMCID: PMC9812223 DOI: 10.1107/s205225252201154x] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Accepted: 11/30/2022] [Indexed: 06/17/2023]
Abstract
The true molecular conformation and the crystal structure of benzo[e]dinaphtho[2,3-a;1',2',3',4'-ghi]fluoranthene, 7,14-diphenylnaphtho[1,2,3,4-cde]bisanthene and 7,16-diphenylnaphtho[1,2,3,4-cde]helianthrene were determined ab initio by 3D electron diffraction. All three molecules are remarkable polycyclic aromatic hydrocarbons. The molecular conformation of two of these compounds could not be determined via classical spectroscopic methods due to the large size of the molecule and the occurrence of multiple and reciprocally connected aromatic rings. The molecular structure of the third molecule was previously considered provisional. These compounds were isolated as by-products in the synthesis of similar products and were at the same time nanocrystalline and available only in very limited amounts. 3D electron diffraction data, taken from submicrometric single crystals, allowed for direct ab initio structure solution and the unbiased determination of the internal molecular conformation. Detailed synthetic routes and spectroscopic analyses are also discussed. Based on many-body perturbation theory simulations, benzo[e]dinaphtho[2,3-a;1',2',3',4'-ghi]fluoranthene may be a promising candidate for triplet-triplet annihilation and 7,14-diphenylnaphtho[1,2,3,4-cde]bisanthene may be a promising candidate for intermolecular singlet fission in the solid state.
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Affiliation(s)
- Iryna Andrusenko
- Center for Material Interfaces, Electron Crystallography, Instituto Italiano di Tecnologia, Pontedera 56025, Italy
| | - Charlie L. Hall
- School of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom
| | - Enrico Mugnaioli
- Center for Material Interfaces, Electron Crystallography, Instituto Italiano di Tecnologia, Pontedera 56025, Italy
- Department of Earth Sciences, University of Pisa, Pisa 56126, Italy
| | - Jason Potticary
- School of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom
| | - Simon R. Hall
- School of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom
| | | | - Siyu Gao
- Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
| | - Kaiji Zhao
- Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
| | - Noa Marom
- Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
| | - Mauro Gemmi
- Center for Material Interfaces, Electron Crystallography, Instituto Italiano di Tecnologia, Pontedera 56025, Italy
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6
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Hall CL, Andrusenko I, Potticary J, Gao S, Liu X, Schmidt W, Marom N, Mugnaioli E, Gemmi M, Hall SR. 3D Electron Diffraction Structure Determination of Terrylene, a Promising Candidate for Intermolecular Singlet Fission. Chemphyschem 2021; 22:1631-1637. [PMID: 34117821 PMCID: PMC8457070 DOI: 10.1002/cphc.202100320] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Revised: 06/05/2021] [Indexed: 12/13/2022]
Abstract
Herein we demonstrate the prowess of the 3D electron diffraction approach by unveiling the structure of terrylene, the third member in the series of peri‐condensed naphthalene analogues, which has eluded structure determination for 65 years. The structure was determined by direct methods using electron diffraction data and corroborated by dispersion‐inclusive density functional theory optimizations. Terrylene crystalizes in the monoclinic space group P21/a, arranging in a sandwich‐herringbone packing motif, similar to analogous compounds. Having solved the crystal structure, we use many‐body perturbation theory to evaluate the excited‐state properties of terrylene in the solid‐state. We find that terrylene is a promising candidate for intermolecular singlet fission, comparable to tetracene and rubrene.
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Affiliation(s)
- Charlie L Hall
- School of Chemistry, University of Bristol, Bristol, BS8 1TS, UK
| | - Iryna Andrusenko
- Istituto Italiano di Tecnologia, Center for Nanotechnology Innovation@NEST, Pisa, 56127, Italy
| | - Jason Potticary
- School of Chemistry, University of Bristol, Bristol, BS8 1TS, UK
| | - Siyu Gao
- Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
| | - Xingyu Liu
- Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
| | | | - Noa Marom
- Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
| | - Enrico Mugnaioli
- Istituto Italiano di Tecnologia, Center for Nanotechnology Innovation@NEST, Pisa, 56127, Italy
| | - Mauro Gemmi
- Istituto Italiano di Tecnologia, Center for Nanotechnology Innovation@NEST, Pisa, 56127, Italy
| | - Simon R Hall
- School of Chemistry, University of Bristol, Bristol, BS8 1TS, UK
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7
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Open questions on the photophysics of ultrafast singlet fission. Commun Chem 2021; 4:85. [PMID: 36697779 PMCID: PMC9814646 DOI: 10.1038/s42004-021-00527-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Accepted: 05/07/2021] [Indexed: 01/28/2023] Open
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8
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Deng GH, Qian Y, Li X, Zhang T, Jiang W, Harutyunyan AR, Chen G, Chen H, Rao Y. Singlet Fission Driven by Anisotropic Vibronic Coupling in Single-Crystalline Pentacene. J Phys Chem Lett 2021; 12:3142-3150. [PMID: 33755478 DOI: 10.1021/acs.jpclett.1c00397] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Vibronic coupling is believed to play an important role in siglet fission, wherein a photoexcited singlet exciton is converted into two triplet excitons. In the present study, we examine the role of vibronic coupling in singlet fission using polarized transient absorption microscopy and ab initio simulations on single-crystalline pentacene. It was found that singlet fission in pentacene is greatly facilitated by the vibrational coherence of a 35.0 cm-1 phonon, where anisotropic coherence persists extensively for a few picoseconds. This coherence-preserving phonon that drives the anisotropic singlet fission is made possible by a unique cross-axial charge-transfer intermediate state. In the same fashion, this phonon was also found to predominantly drive the quantum decohence of a correlated triplet pair to form a decoupled triplet dimer. Moreover, our transient kinetic experimental data illustrates notable directional anisotropicity of the singlet fission rate in single-crystalline pentacene.
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Affiliation(s)
- Gang-Hua Deng
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
| | - Yuqin Qian
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
| | - Xia Li
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
| | - Tong Zhang
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
- Beijing National Laboratory for Molecular Sciences and State Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Wei Jiang
- Argonne Leadership Computing Facility, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | | | - Gugang Chen
- Honda Research Institute, USA, Inc., San Jose, California 95134, United States
| | - Hanning Chen
- Department of Chemistry, American University, Washington, D.C. 20016, United States
| | - Yi Rao
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
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9
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Speelman T, Cunha AV, Kathir RK, Havenith RWA. Electronic couplings for singlet fission: Orbital choice and extrapolation to the complete basis set limit. J Comput Chem 2021; 42:326-333. [PMID: 33616968 PMCID: PMC7898305 DOI: 10.1002/jcc.26458] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2020] [Revised: 11/16/2020] [Accepted: 11/17/2020] [Indexed: 11/05/2022]
Abstract
For the search for promising singlet fission candidates, the calculation of the effective electronic coupling, which is required to estimate the singlet fission rate between the initially excited state (S0S1) and the multiexcitonic state (1TT, two triplets on neighboring molecules, coupled into a singlet), should be sufficiently reliable and fast enough to explore the configuration space. We propose here to modify the calculation of the effective electronic coupling using a nonorthogonal configuration interaction approach by: (a) using only one set of orbitals, optimized for the triplet state of the molecules, to describe all molecular electronic states, and (b) only taking the leading configurations into consideration. Furthermore, we also studied the basis set convergence of the electronic coupling, and we found, by comparison to the complete basis set limit obtained using the cc-pVnZ series of basis sets, that both the aug-cc-pVDZ and 6-311++G** basis sets are a good compromise between accuracy and computational feasibility. The proposed approach enables future work on larger clusters of molecules than dimers.
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Affiliation(s)
- Tom Speelman
- Stratingh Institute for ChemistryUniversity of GroningenGroningenThe Netherlands
| | - Ana V. Cunha
- High Performance Computing GroupSURFSaraAmsterdamThe Netherlands
| | - R. K. Kathir
- Zernike Institute for Advanced MaterialsUniversity of GroningenGroningenThe Netherlands
| | - Remco W. A. Havenith
- Stratingh Institute for ChemistryUniversity of GroningenGroningenThe Netherlands
- Zernike Institute for Advanced MaterialsUniversity of GroningenGroningenThe Netherlands
- Department of Inorganic and Physical ChemistryGhent UniversityGhentBelgium
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10
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Cruz CD, Chronister EL, Bardeen CJ. Using temperature dependent fluorescence to evaluate singlet fission pathways in tetracene single crystals. J Chem Phys 2020; 153:234504. [PMID: 33353314 DOI: 10.1063/5.0031458] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The temperature-dependent fluorescence spectrum, decay rate, and spin quantum beats are examined in single tetracene crystals to gain insight into the mechanism of singlet fission. Over the temperature range of 250 K-500 K, the vibronic lineshape of the emission indicates that the singlet exciton becomes localized at 400 K. The fission process is insensitive to this localization and exhibits Arrhenius behavior with an activation energy of 550 ± 50 cm-1. The damping rate of the triplet pair spin quantum beats in the delayed fluorescence also exhibits an Arrhenius temperature dependence with an activation energy of 165 ± 70 cm-1. All the data for T > 250 K are consistent with direct production of a spatially separated 1(T⋯T) state via a thermally activated process, analogous to spontaneous parametric downconversion of photons. For temperatures in the range of 20 K-250 K, the singlet exciton continues to undergo a rapid decay on the order of 200 ps, leaving a red-shifted emission that decays on the order of 100 ns. At very long times (≈1 µs), a delayed fluorescence component corresponding to the original S1 state can still be resolved, unlike in polycrystalline films. A kinetic analysis shows that the redshifted emission seen at lower temperatures cannot be an intermediate in the triplet production. When considered in the context of other results, our data suggest that the production of triplets in tetracene for temperatures below 250 K is a complex process that is sensitive to the presence of structural defects.
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Affiliation(s)
- Chad D Cruz
- Department of Chemistry, University of California Riverside, Riverside, California 92521, USA
| | - Eric L Chronister
- Department of Chemistry and Biochemistry, University of Nevada, Las Vegas, 4505 S. Maryland Parkway, Las Vegas, Nevada 89154, USA
| | - Christopher J Bardeen
- Department of Chemistry, University of California Riverside, Riverside, California 92521, USA
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11
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Wang G, Zhang C, Liu Z, Wang R, Ma H, Wang X, Xiao M. Singlet Fission Dynamics in Tetracene Single Crystals Probed by Polarization-Dependent Two-Dimensional Electronic Spectroscopy. J Phys Chem A 2020; 124:10447-10456. [PMID: 33290074 DOI: 10.1021/acs.jpca.0c08440] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The exact mechanism of endothermic singlet fission in crystalline polyacene remains to be clarified. It has been elusive whether the excess energy of vibrational hot states and the upper branch of Davydov splitting is important for the energy compensation. Here, we probe the excited-state specified singlet fission dynamics in tetracene single crystals by polarization-dependent two-dimensional electronic spectroscopy (2DES). While a major spectral transfer with a characteristic lifetime of 86 ps is observed to be largely independent of the excitation energy due to formation of the spatially separated triplet pairs (1(T···T)), the excitation-energy dependent subpicosecond dynamics show marked differences for different states probed, implying the possible involvement of a coherently formed triplet pair state (1(TT)). Analysis of coherent vibrational modes suggests the coupling to high energy modes may offset the energy difference between singlet and triplet pair states. Moreover, the beating map of the low frequency mode indicates a vibrational hot state violating the aggregation behavior of Davydov exciton, which can be explained as a resonance of the 1(TT) state. These results suggest that the coherent vibronic mixing between local excitation and triplet pair states is essential for the singlet fission dynamics in molecule aggregates.
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Affiliation(s)
- Guodong Wang
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center for Advanced Microstructures, Nanjing University, Nanjing 210093, P. R. China
| | - Chunfeng Zhang
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center for Advanced Microstructures, Nanjing University, Nanjing 210093, P. R. China
| | - Zhixing Liu
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center for Advanced Microstructures, Nanjing University, Nanjing 210093, P. R. China
| | - Rui Wang
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center for Advanced Microstructures, Nanjing University, Nanjing 210093, P. R. China
| | - Haibo Ma
- School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, P. R. China
| | - Xiaoyong Wang
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center for Advanced Microstructures, Nanjing University, Nanjing 210093, P. R. China
| | - Min Xiao
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center for Advanced Microstructures, Nanjing University, Nanjing 210093, P. R. China.,Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701, United States
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12
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Korovina NV, Pompetti NF, Johnson JC. Lessons from intramolecular singlet fission with covalently bound chromophores. J Chem Phys 2020; 152:040904. [PMID: 32007061 DOI: 10.1063/1.5135307] [Citation(s) in RCA: 67] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Molecular dimers, oligomers, and polymers are versatile components in photophysical and optoelectronic architectures that could impact a variety of applications. We present a perspective on such systems in the field of singlet fission, which effectively multiplies excitons and produces a unique excited state species, the triplet pair. The choice of chromophore and the nature of the attachment between units, both geometrical and chemical, play a defining role in the dynamical scheme that evolves upon photoexcitation. Specific final outcomes (e.g., separated and uncorrelated triplet pairs) are being sought through rational design of covalently bound chromophore architectures built with guidance from recent fundamental studies that correlate structure with excited state population flow kinetics.
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Affiliation(s)
- Nadezhda V Korovina
- National Renewable Energy Laboratory, 15013 Denver West Pkwy, Golden, Colorado 80401, USA
| | - Nicholas F Pompetti
- National Renewable Energy Laboratory, 15013 Denver West Pkwy, Golden, Colorado 80401, USA
| | - Justin C Johnson
- National Renewable Energy Laboratory, 15013 Denver West Pkwy, Golden, Colorado 80401, USA
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13
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Vibronic coherence evolution in multidimensional ultrafast photochemical processes. Nat Commun 2019; 10:5621. [PMID: 31819052 PMCID: PMC6901526 DOI: 10.1038/s41467-019-13503-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Accepted: 11/07/2019] [Indexed: 12/17/2022] Open
Abstract
The complex choreography of electronic, vibrational, and vibronic couplings used by photoexcited molecules to transfer energy efficiently is remarkable, but an unambiguous description of the temporally evolving vibronic states governing these processes has proven experimentally elusive. We use multidimensional electronic-vibrational spectroscopy to identify specific time-dependent excited state vibronic couplings involving multiple electronic states, high-frequency vibrations, and low-frequency vibrations which participate in ultrafast intersystem crossing and subsequent relaxation of a photoexcited transition metal complex. We discover an excited state vibronic mechanism driving long-lived charge separation consisting of an initial electronically-localized vibrational wavepacket which triggers delocalization onto two charge transfer states after propagating for ~600 femtoseconds. Electronic delocalization consequently occurs through nonadiabatic internal conversion driven by a 50 cm-1 coupling resulting in vibronic coherence transfer lasting for ~1 picosecond. This study showcases the power of multidimensional electronic-vibrational spectroscopy to elucidate complex, non-equilibrium energy and charge transfer mechanisms involving multiple molecular coordinates.
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14
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Wang Z, Zhang C, Wang R, Wang G, Wang X, Xiao M. Weakly coupled triplet pair states probed by quantum beating in delayed fluorescence in tetracene crystals. J Chem Phys 2019; 151:134309. [DOI: 10.1063/1.5110188] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Zhiwei Wang
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Chunfeng Zhang
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Rui Wang
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Guodong Wang
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Xiaoyong Wang
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Min Xiao
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
- Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701, USA
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15
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Aggarwal N, Patnaik A. Dimeric conformation sensitive electronic excited states of tetracene congeners and their unconventional non-fluorescent behaviour. J CHEM SCI 2019. [DOI: 10.1007/s12039-019-1626-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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16
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Sandoval-Salinas ME, Carreras A, Casado J, Casanova D. Singlet fission in spiroconjugated dimers. J Chem Phys 2019; 150:204306. [DOI: 10.1063/1.5097048] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Affiliation(s)
- María E. Sandoval-Salinas
- Departament de Ciència de Materials i Química Física and Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, Martí i Franquès 1-11, Barcelona, 08028 Catalunya, Spain
- Donostia International Physics Center (DIPC), Manuel Lardizabal Pasealekua 4, Donostia, Euskadi 20018, Spain
| | - Abel Carreras
- Donostia International Physics Center (DIPC), Manuel Lardizabal Pasealekua 4, Donostia, Euskadi 20018, Spain
| | - Juan Casado
- Department of Physical Chemistry, University of Málaga, Andalucia-Tech, Campus de Teatinos s/n, 29071 Málaga, Spain
| | - David Casanova
- Donostia International Physics Center (DIPC), Manuel Lardizabal Pasealekua 4, Donostia, Euskadi 20018, Spain
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17
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Ellis SR, Dietze DR, Rangel T, Brown-Altvater F, Neaton JB, Mathies RA. Resonance Raman Characterization of Tetracene Monomer and Nanocrystals: Excited State Lattice Distortions With Implications For Efficient Singlet Fission. J Phys Chem A 2019; 123:3863-3875. [PMID: 30952191 DOI: 10.1021/acs.jpca.9b02986] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The characterization of specific phonon modes and exciton states that lead to efficient singlet fission (SF) may be instrumental in the design of the next generation of high-efficiency photovoltaic devices. To this end, we analyze the absolute resonance Raman (RR) cross sections for tetracene (Tc) both as a monomer in solution and as a crystalline solid in an aqueous suspension of nanocrystals. For both systems, a time-dependent wavepacket model is developed that is consistent with the absolute RR cross sections, the magnitude of the absorption cross sections, and the vibronic line shapes of the fluorescence. In the monomer, the intramolecular reorganization energy is between 1500 and 1800 cm-1 and the solvent reorganization energy is 70 cm-1. In nanocrystals, the total reorganization is diminished to less than 600 cm-1. The lowest energy exciton has an estimated intramolecular reorganization energy between 300 and 500 cm-1 while intermolecular librational phonons have a reorganization energy of about 130 cm-1. The diminished reorganization energy of the nanocrystal is interpreted in the context of the delocalization of the band-edge exciton onto about ∼7 molecules. When electron and electron-hole correlations are included within many-body perturbation theory, the polarized absorption spectra of crystalline Tc are calculated and found to be in agreement with experiment. The low-lying exciton states and optically active phonons that contribute to the polarized crystal absorption are identified. The likely role of coherent exciton phonon evolution in the SF process is discussed.
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Affiliation(s)
- Scott R Ellis
- Department of Chemistry, MC 1460 , University of California at Berkeley , Berkeley , California 94720 , United States
| | - Daniel R Dietze
- Department of Chemistry, MC 1460 , University of California at Berkeley , Berkeley , California 94720 , United States
| | - Tonatiuh Rangel
- Department of Physics, MC 7300 , University of California at Berkeley , Berkeley , California 94720 , United States
| | - Florian Brown-Altvater
- Department of Physics, MC 7300 , University of California at Berkeley , Berkeley , California 94720 , United States
| | - Jeffrey B Neaton
- Department of Physics, MC 7300 , University of California at Berkeley , Berkeley , California 94720 , United States
| | - Richard A Mathies
- Department of Chemistry, MC 1460 , University of California at Berkeley , Berkeley , California 94720 , United States
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18
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Abstract
This account aims at providing an understanding of singlet fission, i.e., the photophysical process of a singlet state ( S1) splitting into two triplet states (2 × T1) in molecular chromophores. Since its discovery 50 years ago, the field of singlet fission has enjoyed rapid expansion in the past 8 years. However, there have been lingering confusion and debates on the nature of the all-important triplet pair intermediate states and the definition of singlet fission rates. Here we clarify the confusion from both theoretical and experimental perspectives. We distinguish the triplet pair state that maintains electronic coherence between the two constituent triplets, 1(TT), from one which does not, 1(T···T). Only the rate of formation of 1(T···T) is defined as that of singlet fission. We present distinct experimental evidence for 1(TT), whose formation may occur via incoherent and/or vibronic coherent mechanisms. We discuss the challenges in treating singlet fission beyond the dimer approximation, in understanding the often neglected roles of delocalization on singlet fission rates, and in realizing the much lauded goal of increasing solar energy conversion efficiencies with singlet fission chromophores.
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Affiliation(s)
- Kiyoshi Miyata
- Department of Chemistry , Columbia University , New York , New York 10027 , United States.,Department of Chemistry , Kyushu University , Fukuoka 819-0395 , Japan
| | - Felisa S Conrad-Burton
- Department of Chemistry , Columbia University , New York , New York 10027 , United States
| | - Florian L Geyer
- Department of Chemistry , Columbia University , New York , New York 10027 , United States
| | - X-Y Zhu
- Department of Chemistry , Columbia University , New York , New York 10027 , United States
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19
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Wan Y, Wiederrecht GP, Schaller RD, Johnson JC, Huang L. Transport of Spin-Entangled Triplet Excitons Generated by Singlet Fission. J Phys Chem Lett 2018; 9:6731-6738. [PMID: 30403874 DOI: 10.1021/acs.jpclett.8b02944] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Singlet fission provides a promising route for overcoming the Shockley-Queisser limit in solar cells using organic materials. Despite singlet fission dynamics having been extensively investigated, the transport of the various intermediates in relation to the singlet and triplet states is largely unknown. Here we employ temperature-dependent ultrafast transient absorption microscopy to image the transport of singlet fission intermediates in single crystals of tetracene. These measurements suggest a mobile singlet fission intermediate state at low temperatures, with a diffusion constant of 36 cm2s-1 at 5 K, approaching that for the free singlet excitons, which we attribute to the spin-entangled correlated triplet pair state 1[TT]. These results indicate that 1[TT] could transport with a similar mechanism as the bright singlet excitons, which has important implications in designing materials for singlet fission and spintronic applications.
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Affiliation(s)
- Yan Wan
- College of Chemistry , Beijing Normal University , Beijing 100875 , China
- Department of Chemistry , Purdue University , West Lafayette , Indiana 47907 , United States
| | - Gary P Wiederrecht
- Center for Nanoscale Materials , Argonne National Laboratory , Argonne , Illinois 60439 , United States
| | - Richard D Schaller
- Center for Nanoscale Materials , Argonne National Laboratory , Argonne , Illinois 60439 , United States
- Department of Chemistry , Northwestern University , Evanston , Illinois 60208 , United States
| | - Justin C Johnson
- National Renewable Energy Laboratory , 15013 Denver West Pkwy , Golden , Colorado 80401 , United States
| | - Libai Huang
- Department of Chemistry , Purdue University , West Lafayette , Indiana 47907 , United States
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20
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Zhu T, Huang L. Exciton Transport in Singlet Fission Materials: A New Hare and Tortoise Story. J Phys Chem Lett 2018; 9:6502-6510. [PMID: 30358404 DOI: 10.1021/acs.jpclett.8b02181] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Singlet fission is promising for redistributing the solar spectrum to overcome the Shockley-Queisser limit for single-junction solar cells using molecular materials. Despite recent experimental and theoretical advances in understanding the underlying mechanisms, how exciton transport is coupled to singlet fission dynamics is much less explored. In this Perspective, we examine exciton transport in singlet fission materials, highlighting the use of transient absorption microscopy (TAM) to track the population of different states in both spatial and temporal domains. In contrast to the conventional picture where singlet and triplet excitons migrate independently, TAM measurements of acene single crystals reveal cooperative transport between fast-moving singlet and slow-moving triplet excitons. Such cooperative transport is unique to singlet fission materials and allows hundreds of nanometers triplet migration on the nanosecond time scale, beneficial for solar cell applications. The transport of triplet pair intermediates and general criteria for achieving cooperative singlet-triplet transport are also discussed.
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Affiliation(s)
- Tong Zhu
- Department of Chemistry , Purdue University , West Lafayette , Indiana 47907 , United States
| | - Libai Huang
- Department of Chemistry , Purdue University , West Lafayette , Indiana 47907 , United States
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21
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Pensack RD, Tilley AJ, Grieco C, Purdum GE, Ostroumov EE, Granger DB, Oblinsky DG, Dean JC, Doucette GS, Asbury JB, Loo YL, Seferos DS, Anthony JE, Scholes GD. Striking the right balance of intermolecular coupling for high-efficiency singlet fission. Chem Sci 2018; 9:6240-6259. [PMID: 30090312 PMCID: PMC6062843 DOI: 10.1039/c8sc00293b] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Accepted: 05/31/2018] [Indexed: 12/02/2022] Open
Abstract
Singlet fission is a process that splits collective excitations, or excitons, into two with unity efficiency. This exciton splitting process, unique to molecular photophysics, has the potential to considerably improve the efficiency of optoelectronic devices through more efficient light harvesting. While the first step of singlet fission has been characterized in great detail, subsequent steps critical to achieving overall highly-efficient singlet-to-triplet conversion are only just beginning to become well understood. One of the most elementary suggestions, which has yet to be tested, is that an appropriately balanced coupling is necessary to ensure overall highly efficient singlet fission; that is, the coupling needs to be strong enough so that the first step is fast and efficient, yet weak enough to ensure the independent behavior of the resultant triplets. In this work, we show how high overall singlet-to-triplet conversion efficiencies can be achieved in singlet fission by ensuring that the triplets comprising the triplet pair behave as independently as possible. We show that side chain sterics govern local packing in amorphous pentacene derivative nanoparticles, and that this in turn controls both the rate at which triplet pairs form and the rate at which they decay. We show how compact side chains and stronger couplings promote a triplet pair that effectively couples to the ground state, whereas bulkier side chains promote a triplet pair that appears more like two independent and long-lived triplet excitations. Our results show that the triplet pair is not emissive, that its decay is best viewed as internal conversion rather than triplet-triplet annihilation, and perhaps most critically that, in contrast to a number of recent suggestions, the triplets comprising the initially formed triplet pair cannot be considered independently. This work represents a significant step toward better understanding intermediates in singlet fission, and how molecular packing and couplings govern overall triplet yields.
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Affiliation(s)
- Ryan D Pensack
- Department of Chemistry , Princeton University , Princeton , New Jersey 08544 , USA .
| | - Andrew J Tilley
- Department of Chemistry , University of Toronto , Toronto , Ontario M5S 3H6 , Canada
| | - Christopher Grieco
- Department of Chemistry , The Pennsylvania State University , University Park , Pennsylvania 16802 , USA
| | - Geoffrey E Purdum
- Department of Chemical and Biological Engineering , Princeton University , Princeton , New Jersey 08544 , USA
| | - Evgeny E Ostroumov
- Department of Chemistry , Princeton University , Princeton , New Jersey 08544 , USA .
| | - Devin B Granger
- Department of Chemistry , University of Kentucky , Lexington , Kentucky 40506 , USA .
| | - Daniel G Oblinsky
- Department of Chemistry , Princeton University , Princeton , New Jersey 08544 , USA .
| | - Jacob C Dean
- Department of Chemistry , Princeton University , Princeton , New Jersey 08544 , USA .
| | - Grayson S Doucette
- Department of Chemistry , The Pennsylvania State University , University Park , Pennsylvania 16802 , USA
| | - John B Asbury
- Department of Chemistry , The Pennsylvania State University , University Park , Pennsylvania 16802 , USA
| | - Yueh-Lin Loo
- Department of Chemical and Biological Engineering , Princeton University , Princeton , New Jersey 08544 , USA
- Andlinger Center for Energy and the Environment , Princeton University , Princeton , New Jersey 08544 , USA
| | - Dwight S Seferos
- Department of Chemistry , University of Toronto , Toronto , Ontario M5S 3H6 , Canada
- Department of Chemical Engineering and Applied Chemistry , University of Toronto , Toronto , Ontario M5S 3E5 , Canada
| | - John E Anthony
- Department of Chemistry , University of Kentucky , Lexington , Kentucky 40506 , USA .
| | - Gregory D Scholes
- Department of Chemistry , Princeton University , Princeton , New Jersey 08544 , USA .
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22
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Chen L, Zhao Y. Finite temperature dynamics of a Holstein polaron: The thermo-field dynamics approach. J Chem Phys 2018; 147:214102. [PMID: 29221386 DOI: 10.1063/1.5000823] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Combining the multiple Davydov D2 Ansatz with the method of thermo-field dynamics, we study finite temperature dynamics of a Holstein polaron on a lattice. It has been demonstrated, using the hierarchy equations of motion method as a benchmark, that our approach provides an efficient, robust description of finite temperature dynamics of the Holstein polaron in the simultaneous presence of diagonal and off-diagonal exciton-phonon coupling. The method of thermo-field dynamics handles temperature effects in the Hilbert space with key numerical advantages over other treatments of finite-temperature dynamics based on quantum master equations in the Liouville space or wave function propagation with Monte Carlo importance sampling. While for weak to moderate diagonal coupling temperature increases inhibit polaron mobility, it is found that off-diagonal coupling induces phonon-assisted transport that dominates at high temperatures. Results on the mean square displacements show that band-like transport features dominate the diagonal coupling cases, and there exists a crossover from band-like to hopping transport with increasing temperature when including off-diagonal coupling. As a proof of concept, our theory provides a unified treatment of coherent and incoherent transport in molecular crystals and is applicable to any temperature.
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Affiliation(s)
- Lipeng Chen
- Division of Materials Science, Nanyang Technological University, Singapore 639798, Singapore
| | - Yang Zhao
- Division of Materials Science, Nanyang Technological University, Singapore 639798, Singapore
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23
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Abstract
Singlet fission is a photophysical reaction in which a singlet excited electronic state splits into two spin-triplet states. Singlet fission was discovered more than 50 years ago, but the interest in this process has gained a lot of momentum in the past decade due to its potential as a way to boost solar cell efficiencies. This review presents and discusses the most recent advances with respect to the theoretical and computational studies on the singlet fission phenomenon. The work revisits important aspects regarding electronic states involved in the process, the evaluation of fission rates and interstate couplings, the study of the excited state dynamics in singlet fission, and the advances in the design and characterization of singlet fission compounds and materials such as molecular dimers, polymers, or extended structures. Finally, the review tries to pinpoint some aspects that need further improvement and proposes future lines of research for theoretical and computational chemists and physicists in order to further push the understanding and applicability of singlet fission.
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Affiliation(s)
- David Casanova
- Kimika Fakultatea , Euskal Herriko Unibertsitatea (UPV/EHU) and Donostia International Physics Center (DIPC) , P.K. 1072, 20080 Donostia , Euskadi, Spain.,IKERBASQUE, Basque, Foundation for Science , 48013 Bilbao , Euskadi, Spain
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24
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Refaely-Abramson S, da Jornada FH, Louie SG, Neaton JB. Origins of Singlet Fission in Solid Pentacene from an ab initio Green's Function Approach. PHYSICAL REVIEW LETTERS 2017; 119:267401. [PMID: 29328724 DOI: 10.1103/physrevlett.119.267401] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Indexed: 05/24/2023]
Abstract
We develop a new first-principles approach to predict and understand rates of singlet fission with an ab initio Green's-function formalism based on many-body perturbation theory. Starting with singlet and triplet excitons computed from a GW plus Bethe-Salpeter equation approach, we calculate the exciton-biexciton coupling to lowest order in the Coulomb interaction, assuming a final state consisting of two noninteracting spin-correlated triplets with finite center-of-mass momentum. For crystalline pentacene, symmetries dictate that the only purely Coulombic fission decay process from a bright singlet state requires a final state consisting of two inequivalent nearly degenerate triplets of nonzero, equal and opposite, center-of-mass momenta. For such a process, we predict a singlet lifetime of 30-70 fs, in very good agreement with experimental data, indicating that this process can dominate singlet fission in crystalline pentacene. Our approach is general and provides a framework for predicting and understanding multiexciton interactions in solids.
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Affiliation(s)
- Sivan Refaely-Abramson
- Department of Physics, University of California Berkeley, Berkeley, California 94720, USA
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Felipe H da Jornada
- Department of Physics, University of California Berkeley, Berkeley, California 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Steven G Louie
- Department of Physics, University of California Berkeley, Berkeley, California 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Jeffrey B Neaton
- Department of Physics, University of California Berkeley, Berkeley, California 94720, USA
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
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25
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Sun KW, Yao Y. Beating maps of singlet fission: Simulation of coherent two-dimensional electronic spectroscopy by Davydov ansatz in organic molecules. J Chem Phys 2017; 147:224905. [DOI: 10.1063/1.5005564] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- Ke-Wei Sun
- School of Science, Hangzhou Dianzi University, Hangzhou 310018, China
| | - Yao Yao
- Department of Physics, South China University of Technology, Guangzhou 510640, China
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26
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Cook JD, Carey TJ, Arias DH, Johnson JC, Damrauer NH. Solvent-Controlled Branching of Localized versus Delocalized Singlet Exciton States and Equilibration with Charge Transfer in a Structurally Well-Defined Tetracene Dimer. J Phys Chem A 2017; 121:9229-9242. [DOI: 10.1021/acs.jpca.7b09458] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jasper D. Cook
- Department
of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, United States
| | - Thomas J. Carey
- Department
of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, United States
| | - Dylan H. Arias
- National Renewable Energy Laboratory, Golden, Colorado 80401, United States
| | - Justin C. Johnson
- National Renewable Energy Laboratory, Golden, Colorado 80401, United States
| | - Niels H. Damrauer
- Department
of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, United States
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27
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Miyata K, Kurashige Y, Watanabe K, Sugimoto T, Takahashi S, Tanaka S, Takeya J, Yanai T, Matsumoto Y. Coherent singlet fission activated by symmetry breaking. Nat Chem 2017; 9:983-989. [PMID: 28937675 DOI: 10.1038/nchem.2784] [Citation(s) in RCA: 124] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Accepted: 04/21/2017] [Indexed: 12/20/2022]
Abstract
Singlet fission, in which a singlet exciton is converted to two triplet excitons, is a process that could be beneficial in photovoltaic applications. A full understanding of the dynamics of singlet fission in molecular systems requires detailed knowledge of the relevant potential energy surfaces and their (conical) intersections. However, obtaining such information is a nontrivial task, particularly for molecular aggregates. Here we investigate singlet fission in rubrene crystals using transient absorption spectroscopy and state-of-the-art quantum chemical calculations. We observe a coherent and ultrafast singlet-fission channel as well as the well-known and conventional thermally assisted incoherent channel. This coherent channel is accessible because the conical intersection for singlet fission on the excited-state potential energy surface is located very close to the equilibrium position of the ground-state potential energy surface and also because of the excitation of an intermolecular symmetry-breaking mode, which activates the electronic coupling necessary for singlet fission.
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Affiliation(s)
- Kiyoshi Miyata
- Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Yuki Kurashige
- Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.,Institute for Molecular Science, Okazaki 444-8585, Japan.,PRESTO, Japan Science and Technology Agency (JST), Honcho 4-1-8, Kawaguchi, Saitama 332-0012, Japan
| | - Kazuya Watanabe
- Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Toshiki Sugimoto
- Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.,PRESTO, Japan Science and Technology Agency (JST), Honcho 4-1-8, Kawaguchi, Saitama 332-0012, Japan
| | - Shota Takahashi
- Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Shunsuke Tanaka
- Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Jun Takeya
- Department of Advanced Materials Science, Graduate School of Frontier Sciences, The University of Tokyo, Chiba 277-8561, Japan
| | - Takeshi Yanai
- Institute for Molecular Science, Okazaki 444-8585, Japan
| | - Yoshiyasu Matsumoto
- Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
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28
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Carey TJ, Snyder JL, Miller EG, Sammakia T, Damrauer NH. Synthesis of Geometrically Well-Defined Covalent Acene Dimers for Mechanistic Exploration of Singlet Fission. J Org Chem 2017; 82:4866-4874. [DOI: 10.1021/acs.joc.7b00602] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Thomas J. Carey
- Department of Chemistry and
Biochemistry, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Jamie L. Snyder
- Department of Chemistry and
Biochemistry, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Ethan G. Miller
- Department of Chemistry and
Biochemistry, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Tarek Sammakia
- Department of Chemistry and
Biochemistry, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Niels H. Damrauer
- Department of Chemistry and
Biochemistry, University of Colorado Boulder, Boulder, Colorado 80309, United States
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29
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Pithan L, Beyer P, Bogula L, Zykov A, Schäfer P, Rawle J, Nicklin C, Opitz A, Kowarik S. Direct Photoalignment and Optical Patterning of Molecular Thin Films. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2017; 29:1604382. [PMID: 27906475 DOI: 10.1002/adma.201604382] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2016] [Revised: 10/02/2016] [Indexed: 06/06/2023]
Abstract
A novel strategy for direct photoalignment of molecular materials using optothermal re-orientation is introduced. Photoalignment for molecular materials such as the organic semiconductor tetracene is shown, without relying on additional photoreactive dopants or alignment layers. Patterning and polarized light emission, e.g., for polarized organic light emitting diodes is demonstrated.
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Affiliation(s)
- Linus Pithan
- Institut für Physik, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489, Berlin, Germany
| | - Paul Beyer
- Institut für Physik, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489, Berlin, Germany
| | - Laura Bogula
- Institut für Physik, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489, Berlin, Germany
| | - Anton Zykov
- Institut für Physik, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489, Berlin, Germany
| | - Peter Schäfer
- Institut für Physik, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489, Berlin, Germany
| | - Jonathan Rawle
- Diamond Light Source Ltd, Harwell Science & Innovation Campus, Didcot, Oxfordshire, OX11 0DE, UK
| | - Chris Nicklin
- Diamond Light Source Ltd, Harwell Science & Innovation Campus, Didcot, Oxfordshire, OX11 0DE, UK
| | - Andreas Opitz
- Institut für Physik, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489, Berlin, Germany
| | - Stefan Kowarik
- Institut für Physik, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489, Berlin, Germany
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30
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Cook JD, Carey TJ, Damrauer NH. Solution-Phase Singlet Fission in a Structurally Well-Defined Norbornyl-Bridged Tetracene Dimer. J Phys Chem A 2016; 120:4473-81. [PMID: 27291516 DOI: 10.1021/acs.jpca.6b04367] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The photophysics of a norbornyl-bridged covalent tetracene (Tc) dimer BT1 and a monomer analogue Tc-e were studied in room-temperature nonpolar solvents. Notably in BT1, a Davydov-split band is observed in UV absorption, heralding interchromophore electronic interactions. Emission spectra indicate an acene-like vibronic progression mirroring the lowest-energy visible absorption. For BT1, this argues against excited-state excimer formation. Evidence of intramolecular singlet fission (SF) comes from a comparison of time-resolved emission decay signals collected for BT1 versus Tc-e in toluene. In BT1, the multiexcitonic (1)TT state is produced in 70 ns in 6% yield. A ratio of fission versus fusion rate constants provides an experimental measure of the SF reaction free energy at 52 meV in good agreement with previous calculations. The low SF yield corroborates our expectations that orbital symmetry effects on diabatic coupling for SF are important for dimers that cannot rely on more favorable thermodynamics.
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Affiliation(s)
- Jasper D Cook
- Department of Chemistry and Biochemistry, University of Colorado , Boulder Colorado 80309, United States
| | - Thomas J Carey
- Department of Chemistry and Biochemistry, University of Colorado , Boulder Colorado 80309, United States
| | - Niels H Damrauer
- Department of Chemistry and Biochemistry, University of Colorado , Boulder Colorado 80309, United States
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31
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Korovina NV, Das S, Nett Z, Feng X, Joy J, Haiges R, Krylov AI, Bradforth SE, Thompson ME. Singlet Fission in a Covalently Linked Cofacial Alkynyltetracene Dimer. J Am Chem Soc 2016; 138:617-27. [PMID: 26693957 DOI: 10.1021/jacs.5b10550] [Citation(s) in RCA: 185] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Singlet fission is a process in which a singlet exciton converts into two triplet excitons. To investigate this phenomenon, we synthesized two covalently linked 5-ethynyl-tetracene (ET) dimers with differing degrees of intertetracene overlap: BET-X, with large, cofacial overlap of tetracene π-orbitals, and BET-B, with twisted arrangement between tetracenes exhibits less overlap between the tetracene π-orbitals. The two compounds were crystallographically characterized and studied by absorption and emission spectroscopy in solution, in PMMA and neat thin films. The results show that singlet fission occurs within 1 ps in an amorphous thin film of BET-B with high efficiency (triplet yield: 154%). In solution and the PMMA matrix the S1 of BET-B relaxes to a correlated triplet pair (1)(T1T1) on a time scale of 2 ps, which decays to the ground state without forming separated triplets, suggesting that triplet energy transfer from (1)(T1T1) to a nearby chromophore is essential for producing free triplets. In support of this hypothesis, selective excitation of BET-B doped into a thin film of diphenyltetracene (DPT) leads to formation of the (1)(T1T1) state of BET-B, followed by generation of both DPT and BET-B triplets. For the structurally cofacial BET-X, an intermediate forms in <180 fs and returns to the ground state more rapidly than BET-B. First-principles calculations predict a 2 orders of magnitude faster rate of singlet fission to the (1)(T1T1) state in BET-B relative to that of crystalline tetracene, attributing the rate increase to greater coupling between the S1 and (1)(T1T1) states and favorable energetics for formation of the separated triplets.
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Affiliation(s)
- Nadezhda V Korovina
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
| | - Saptaparna Das
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
| | - Zachary Nett
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
| | - Xintian Feng
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
| | - Jimmy Joy
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
| | - Ralf Haiges
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
| | - Anna I Krylov
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
| | - Stephen E Bradforth
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
| | - Mark E Thompson
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
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32
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Damrauer NH, Snyder JL. Symmetry-directed control of electronic coupling for singlet fission in covalent bis-acene dimers. J Phys Chem Lett 2015; 6:4456-4462. [PMID: 26505732 DOI: 10.1021/acs.jpclett.5b02186] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
While singlet fission (SF) has developed in recent years within material settings, much less is known about its control in covalent dimers. Such platforms are of fundamental importance and may also find practical use in next-generation dye-sensitized solar cell applications or for seeding SF at interfaces following exciton transport. Here, facile theoretical tools based on Boys localization methods are used to predict diabatic coupling for SF via determination of one-electron orbital coupling matrix elements. The results expose important design rules that are rooted in point group symmetry. For Cs-symmetric dimers, pathways for SF that are mediated by virtual charge transfer excited states destructively interfere with negative impact on the magnitude of diabatic coupling for SF. When dimers have C2 symmetry, constructive interference is enabled for certain readily achievable interchromophore orientations. Three sets of dimers exploiting these ideas are explored: a bis-tetracene pair and two sets of aza-substituted tetracene dimers. Remarkable control is shown. In one aza-substituted set, symmetry has no impact on SF reaction thermodynamics but leads to a 16-fold manipulation in SF diabatic coupling. This translates to a difference of nearly 300 in kSF with the faster of the two dimers (C2) being predicted to undergo the process on a nearly ultrafast 1.5 ps time scale.
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Affiliation(s)
- Niels H Damrauer
- Department of Chemistry and Biochemistry, University of Colorado , Boulder, Colorado 80309, United States
| | - Jamie L Snyder
- Department of Chemistry and Biochemistry, University of Colorado , Boulder, Colorado 80309, United States
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33
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Teichen PE, Eaves JD. Collective aspects of singlet fission in molecular crystals. J Chem Phys 2015; 143:044118. [PMID: 26233118 DOI: 10.1063/1.4922644] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
We present a model to describe collective features of singlet fission in molecular crystals and analyze it using many-body theory. The model we develop allows excitonic states to delocalize over several chromophores which is consistent with the character of the excited states in many molecular crystals, such as the acenes, where singlet fission occurs. As singlet states become more delocalized and triplet states more localized, the rate of singlet fission increases. We also determine the conditions under which the two triplets resulting from fission are correlated. Using the Bethe Ansatz and an entanglement measure for indistinguishable bipartite systems, we calculate the triplet-triplet entanglement as a function of the biexciton interaction strength. The biexciton interaction can produce bound biexciton states and provides a source of entanglement between the two triplets even when the triplets are spatially well separated. Significant entanglement between the triplet pair occurs well below the threshold for bound pair formation. Our results paint a dynamical picture that helps to explain why fission has been observed to be more efficient in molecular crystals than in their covalent dimer analogues and have consequences for photovoltaic efficiency models that assume that the two triplets can be extracted independently.
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Affiliation(s)
- Paul E Teichen
- Department of Chemistry and Biochemistry, The University of Colorado at Boulder, Boulder, Colorado 80309, USA
| | - Joel D Eaves
- Department of Chemistry and Biochemistry, The University of Colorado at Boulder, Boulder, Colorado 80309, USA
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34
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Arias DH, Ryerson JL, Cook JD, Damrauer NH, Johnson JC. Polymorphism influences singlet fission rates in tetracene thin films. Chem Sci 2015; 7:1185-1191. [PMID: 29910873 PMCID: PMC5975788 DOI: 10.1039/c5sc03535j] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Accepted: 11/05/2015] [Indexed: 12/21/2022] Open
Abstract
We report the effect of crystal structure and crystallite grain size on singlet fission (SF) in polycrystalline tetracene, one of the most widely studied SF and organic semiconductor materials. SF has been comprehensively studied in one polymoprh (Tc I), but not in the other, less stable polymorph (Tc II). Using carefully controlled thermal evaporation deposition conditions and high sensitivity ultrafast transient absorption spectroscopy, we found that for large crystallite size samples, SF in nearly pure Tc II films is significantly faster than SF in Tc I films. We also discovered that crystallite size has a minimal impact on the SF rate in Tc II films, but a significant influence in Tc I films. Large crystallites exhibit SF times of 125 ps and 22 ps in Tc I and Tc II, respectively, whereas small crystallites have SF times of 31 ps and 33 ps. Our results demonstrate first, that attention must be paid to polymorphism in obtaining a self-consistent rate picture for SF in tetracene and second, that control of polymorphism can play a significant role towards achieving a mechanistic understanding of SF in polycrystalline systems. In this latter context we show that conventional theory based on non-covalent tetracene couplings is insufficient, thus highlighting the need for models that capture the delocalized and highly mobile nature of excited states in elucidating the full photophysical picture.
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Affiliation(s)
- Dylan H Arias
- National Renewable Energy Laboratory , Golden , Colorado 80401 , USA . .,Department of Chemistry and Biochemistry , University of Colorado , Boulder , Colorado 80309 , USA .
| | - Joseph L Ryerson
- National Renewable Energy Laboratory , Golden , Colorado 80401 , USA . .,Department of Chemistry and Biochemistry , University of Colorado , Boulder , Colorado 80309 , USA .
| | - Jasper D Cook
- Department of Chemistry and Biochemistry , University of Colorado , Boulder , Colorado 80309 , USA .
| | - Niels H Damrauer
- Department of Chemistry and Biochemistry , University of Colorado , Boulder , Colorado 80309 , USA .
| | - Justin C Johnson
- National Renewable Energy Laboratory , Golden , Colorado 80401 , USA .
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35
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Dong S, Trivedi D, Chakrabortty S, Kobayashi T, Chan Y, Prezhdo OV, Loh ZH. Observation of an Excitonic Quantum Coherence in CdSe Nanocrystals. NANO LETTERS 2015; 15:6875-82. [PMID: 26359970 DOI: 10.1021/acs.nanolett.5b02786] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Recent observations of excitonic coherences within photosynthetic complexes suggest that quantum coherences could enhance biological light harvesting efficiencies. Here, we employ optical pump-probe spectroscopy with few-femtosecond pulses to observe an excitonic quantum coherence in CdSe nanocrystals, a prototypical artificial light harvesting system. This coherence, which encodes the high-speed migration of charge over nanometer length scales, is also found to markedly alter the displacement amplitudes of phonons, signaling dynamics in the non-Born-Oppenheimer regime.
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Affiliation(s)
- Shuo Dong
- Division of Chemistry and Biological Chemistry, and Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University , 21 Nanyang Link, Singapore 637371, Singapore
| | - Dhara Trivedi
- Department of Physics and Astronomy, University of Rochester , Rochester, New York 14627, United States
| | - Sabyasachi Chakrabortty
- Department of Chemistry, National University of Singapore , 3 Science Drive 3, Singapore 117543, Singapore
| | - Takayoshi Kobayashi
- Advanced Ultrafast Laser Research Center, The University of Electro-Communications , 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585, Japan
- JST, CREST, K'Gobancho , 7 Gobancho, Chiyoda-ku, Tokyo 102-0076, Japan
- Department of Electrophysics, National Chiao-Tung University , Hsinchu 300, Taiwan
- Institute of Laser Engineering, Osaka University , 2-6 Yamada-oka, Suita, Osaka 565-0971, Japan
| | - Yinthai Chan
- Department of Chemistry, National University of Singapore , 3 Science Drive 3, Singapore 117543, Singapore
- Institute of Materials Research & Engineering, A*STAR , 3 Research Link, Singapore 117602, Singapore
| | - Oleg V Prezhdo
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
| | - Zhi-Heng Loh
- Division of Chemistry and Biological Chemistry, and Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University , 21 Nanyang Link, Singapore 637371, Singapore
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36
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Wang R, Zhang C, Zhang B, Liu Y, Wang X, Xiao M. Magnetic dipolar interaction between correlated triplets created by singlet fission in tetracene crystals. Nat Commun 2015; 6:8602. [PMID: 26456368 PMCID: PMC4633952 DOI: 10.1038/ncomms9602] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Accepted: 09/09/2015] [Indexed: 01/15/2023] Open
Abstract
Singlet fission can potentially break the Shockley–Queisser efficiency limit in single-junction solar cells by splitting one photoexcited singlet exciton (S1) into two triplets (2T1) in organic semiconductors. A dark multiexciton state has been proposed as the intermediate connecting S1 to 2T1. However, the exact nature of this multiexciton state, especially how the doubly excited triplets interact, remains elusive. Here we report a quantitative study on the magnetic dipolar interaction between singlet-fission-induced correlated triplets in tetracene crystals by monitoring quantum beats relevant to the multiexciton sublevels at room temperature. The resonances of multiexciton sublevels approached by tuning an external magnetic field are observed to be avoided, which agrees well with the theoretical predictions considering a magnetic dipolar interaction of ∼0.008 GHz. Our work quantifies the magnetic dipolar interaction in certain organic materials and marks an important step towards understanding the underlying physics of the multiexciton state in singlet fission. The exact mechanism of singlet fission remains unresolved. Here, Wang et al. report a quantitative measurement of the interaction between singlet-fission-induced correlated triplets in tetracene crystals with quantum beat spectroscopy, indicating the role played by exciton delocalization in singlet fission.
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Affiliation(s)
- Rui Wang
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China
| | - Chunfeng Zhang
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China.,Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Bo Zhang
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China.,Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Yunlong Liu
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China.,Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Xiaoyong Wang
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China.,Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Min Xiao
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China.,Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.,Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701, USA
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37
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Wan Y, Guo Z, Zhu T, Yan S, Johnson J, Huang L. Cooperative singlet and triplet exciton transport in tetracene crystals visualized by ultrafast microscopy. Nat Chem 2015; 7:785-92. [DOI: 10.1038/nchem.2348] [Citation(s) in RCA: 163] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Accepted: 09/14/2015] [Indexed: 12/22/2022]
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38
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Abstract
The dependence of exciton dynamics on the crystalline morphology of tetracene is investigated using time-resolved photoluminescence. Single crystals exhibit relatively slow singlet decays with times that range from 130 to 300 ps depending on the sample. This decay has an activation energy of ∼450 cm(-1) over the temperature range of 200-400 K. Single-crystal samples also exhibit more pronounced quantum beats due to the triplet pair spin coherences. Polycrystalline thin films grown by thermal evaporation have singlet decay times on the order of 70-90 ps with a much weaker temperature dependence. Many thin-film samples also exhibit a red-shifted excimer-like emission. When a polycrystalline thin film is thermally annealed to produce larger crystal domains, single-crystal behavior is recovered. We hypothesize that the different dynamics arise from the ability of singlet excitons in the thin films to sample regions with defects or packing motifs that accelerate singlet fission.
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Affiliation(s)
- Geoffrey B Piland
- Department of Chemistry, University of California, Riverside, Riverside, California 92506, United States
| | - Christopher J Bardeen
- Department of Chemistry, University of California, Riverside, Riverside, California 92506, United States
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39
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Eaton SW, Miller SA, Margulies EA, Shoer LE, Schaller RD, Wasielewski MR. Singlet exciton fission in thin films of tert-butyl-substituted terrylenes. J Phys Chem A 2015; 119:4151-61. [PMID: 25856414 DOI: 10.1021/acs.jpca.5b02719] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Two terrylene chromophores, 2,5,10,13-tetra(tert-butyl)terrylene (1) and 2,5-di(tert-butyl)terrylene (2), were synthesized and studied to determine their singlet exciton fission (SF) efficiencies. Compound 1 crystallizes in one-dimensional stacks, whereas 2 packs in a slip-stacked, herringbone pattern of dimers motif. Strongly quenched fluorescence and rapid singlet exciton decay dynamics are observed in vapor-deposited thin films of 1 and 2. Phosphorescence measurements on thin films of 1 and 2 show that SF is only 70 meV endoergic for these chromophores. Femtosecond transient absorption experiments using low laser fluences on these films reveal rapid triplet exciton formation for both 1 (τ = 120 ± 10 ps) and 2 (τ = 320 ± 20 ps) that depends strongly on film crystallinity. The transient absorption data are consistent with formation of an excimer state prior to SF. Triplet exciton yield measurements indicate nearly quantitative SF in thin films of both chromophores in highly crystalline solvent-vapor-annealed films: 170 ± 20% for 1 and 200 ± 30% for 2. These results show that significantly different crystal morphologies of the same chromophore can both result in high-efficiency SF provided that the energetics are favorable.
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Affiliation(s)
| | | | | | | | - Richard D Schaller
- §Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois 60439-4803, United States
| | - Michael R Wasielewski
- §Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois 60439-4803, United States
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40
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Alguire EC, Subotnik JE, Damrauer NH. Exploring Non-Condon Effects in a Covalent Tetracene Dimer: How Important Are Vibrations in Determining the Electronic Coupling for Singlet Fission? J Phys Chem A 2014; 119:299-311. [DOI: 10.1021/jp510777c] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- Ethan C. Alguire
- Department
of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, Pennsylvania 19104-6323, United States
| | - Joseph E. Subotnik
- Department
of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, Pennsylvania 19104-6323, United States
| | - Niels H. Damrauer
- Department
of Chemistry and Biochemistry, University of Colorado at Boulder, Boulder, Colorado 80309, United States
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41
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Zhang B, Zhang C, Xu Y, Wang R, He B, Liu Y, Zhang S, Wang X, Xiao M. Polarization-dependent exciton dynamics in tetracene single crystals. J Chem Phys 2014; 141:244303. [DOI: 10.1063/1.4904385] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Affiliation(s)
- Bo Zhang
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Chunfeng Zhang
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Yanqing Xu
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Rui Wang
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Bin He
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Yunlong Liu
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Shimeng Zhang
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Xiaoyong Wang
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Min Xiao
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
- Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701, USA
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42
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Birech Z, Schwoerer M, Schmeiler T, Pflaum J, Schwoerer H. Ultrafast dynamics of excitons in tetracene single crystals. J Chem Phys 2014; 140:114501. [PMID: 24655187 DOI: 10.1063/1.4867696] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Ultrafast exciton dynamics in free standing 200 nm thin tetracene single crystals were studied at room temperature by femtosecond transient absorption spectroscopy in the visible spectral range. The complex spectrally overlapping transient absorption traces of single crystals were systematically deconvoluted. From this, the ultrafast dynamics of the ground, excited, and transition states were identified including singlet exciton fission into two triplet excitons. Fission is generated through both, direct fission of higher singlet states S(n) on a sub-picosecond timescale, and thermally activated fission of the singlet exciton S1 on a 40 ps timescale. The high energy Davydov component of the S1 exciton is proposed to undergo fission on a sub-picoseconds timescale. At high density of triplet excitons their mutual annihilation (triplet-triplet annihilation) occurs on a <10 ps timescale.
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Affiliation(s)
- Zephania Birech
- Laser Research Institute, Stellenbosch University, Stellenbosch 7600, South Africa
| | - Markus Schwoerer
- Department of Physics, University of Bayreuth, Bayreuth, Germany
| | - Teresa Schmeiler
- Experimental Physics VI, University of Würzburg and Bavarian Center for Applied Energy Research, Würzburg, Germany
| | - Jens Pflaum
- Experimental Physics VI, University of Würzburg and Bavarian Center for Applied Energy Research, Würzburg, Germany
| | - Heinrich Schwoerer
- Laser Research Institute, Stellenbosch University, Stellenbosch 7600, South Africa
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43
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Wilson MWB, Rao A, Johnson K, Gélinas S, di Pietro R, Clark J, Friend RH. Temperature-independent singlet exciton fission in tetracene. J Am Chem Soc 2014; 135:16680-8. [PMID: 24148017 DOI: 10.1021/ja408854u] [Citation(s) in RCA: 126] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We use transient absorption spectroscopy to demonstrate that the dynamics of singlet exciton fission in tetracene are independent of temperature (10–270 K). Low-intensity, broad-band measurements allow the identification of spectral features while minimizing bimolecular recombination. Hence, by directly observing both species, we find that the time constant for the conversion of singlets to triplet pairs is ~90 ps. However, in contrast to pentacene, where fission is effectively unidirectional, we confirm that the emissive singlet in tetracene is readily regenerated from spin-correlated "geminate" triplets following fission, leading to equilibrium dynamics. Although free triplets are efficiently generated at room temperature, the interplay of superradiance and frustrated triplet diffusion contributes to a nearly 20-fold increase in the steady-state fluorescence as the sample is cooled. Together, these results require that singlets and triplet pairs in tetracene are effectively degenerate in energy, and begin to reconcile the temperature dependence of many macroscopic observables with a fission process which does not require thermal activation.
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44
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Zhang B, Zhang C, Wang R, Tan Z, Liu Y, Guo W, Zhai X, Cao Y, Wang X, Xiao M. Nonlinear Density Dependence of Singlet Fission Rate in Tetracene Films. J Phys Chem Lett 2014; 5:3462-3467. [PMID: 26278594 DOI: 10.1021/jz501736y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Singlet fission holds the potential to dramatically improve the efficiency of solar energy conversion by creating two triplet excitons from one photoexcited singlet exciton in organic semiconductors. It is generally assumed that the singlet-fission rate is linearly dependent on the exciton density. Here we experimentally show that the rate of singlet fission has a nonlinear dependence on the density of photoexcited singlet excitons in tetracene films with small crystalline grains. We disentangle the spectrotemporal features of singlet and triplet dynamics from ultrafast spectroscopic data with the algorithm of singular value decomposition. The correlation between their temporal dynamics indicates a superlinear dependence of fission rate on the density of singlet excitons, which may arise from excitonic interactions.
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Affiliation(s)
| | | | | | - Zhanao Tan
- ‡New and Renewable Energy of Beijing Key Laboratory, School of Renewable Energy, North China Electric Power University, Beijing 102206, China
| | | | | | | | | | | | - Min Xiao
- §Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701, United States
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45
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Kee TW. Femtosecond Pump-Push-Probe and Pump-Dump-Probe Spectroscopy of Conjugated Polymers: New Insight and Opportunities. J Phys Chem Lett 2014; 5:3231-40. [PMID: 26276338 DOI: 10.1021/jz501549h] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Conjugated polymers are an important class of soft materials that exhibit a wide range of applications. The excited states of conjugated polymers, often referred to as excitons, can either deactivate to yield the ground state or dissociate in the presence of an electron acceptor to form charge carriers. These interesting properties give rise to their luminescence and the photovoltaic effect. Femtosecond spectroscopy is a crucial tool for studying conjugated polymers. Recently, more elaborate experimental configurations utilizing three optical pulses, namely, pump-push-probe and pump-dump-probe, have been employed to investigate the properties of excitons and charge-transfer states of conjugated polymers. These studies have revealed new insight into femtosecond torsional relaxation and detrapping of bound charge pairs of conjugated polymers. This Perspective highlights (1) the recent achievements by several research groups in using pump-push-probe and pump-dump-probe spectroscopy to study conjugated polymers and (2) future opportunities and potential challenges of these techniques.
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Affiliation(s)
- Tak W Kee
- Department of Chemistry, The University of Adelaide, Adelaide, South Australia 5005, Australia
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46
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Affiliation(s)
- Hanning Chen
- Department
of Chemistry, The George Washington University, 725 21st Street, Northwest, Washington, District of Columbia 20052, United States
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Koch M, Perumal K, Blacque O, Garg JA, Saiganesh R, Kabilan S, Balasubramanian KK, Venkatesan K. Metal‐Free Triplet Phosphors with High Emission Efficiency and High Tunability. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201402199] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Michael Koch
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH‐8057 Zurich (Switzerland)
| | - Karthikeyan Perumal
- Shasun Research Centre, 27 Vandaloor‐Kelambakkam Road, Keelakottaiyur, Chennai‐600048 (India)
- Department of Chemistry, Annamalai University, Annamalai Nagar, Chidambaram‐600002 (India)
| | - Olivier Blacque
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH‐8057 Zurich (Switzerland)
| | - Jai Anand Garg
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH‐8057 Zurich (Switzerland)
| | - Ramanathan Saiganesh
- Shasun Research Centre, 27 Vandaloor‐Kelambakkam Road, Keelakottaiyur, Chennai‐600048 (India)
| | | | | | - Koushik Venkatesan
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH‐8057 Zurich (Switzerland)
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Koch M, Perumal K, Blacque O, Garg JA, Saiganesh R, Kabilan S, Balasubramanian KK, Venkatesan K. Metal‐Free Triplet Phosphors with High Emission Efficiency and High Tunability. Angew Chem Int Ed Engl 2014; 53:6378-82. [DOI: 10.1002/anie.201402199] [Citation(s) in RCA: 91] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Indexed: 11/05/2022]
Affiliation(s)
- Michael Koch
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH‐8057 Zurich (Switzerland)
| | - Karthikeyan Perumal
- Shasun Research Centre, 27 Vandaloor‐Kelambakkam Road, Keelakottaiyur, Chennai‐600048 (India)
- Department of Chemistry, Annamalai University, Annamalai Nagar, Chidambaram‐600002 (India)
| | - Olivier Blacque
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH‐8057 Zurich (Switzerland)
| | - Jai Anand Garg
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH‐8057 Zurich (Switzerland)
| | - Ramanathan Saiganesh
- Shasun Research Centre, 27 Vandaloor‐Kelambakkam Road, Keelakottaiyur, Chennai‐600048 (India)
| | | | | | - Koushik Venkatesan
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH‐8057 Zurich (Switzerland)
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Schrauben JN, Ryerson JL, Michl J, Johnson JC. Mechanism of singlet fission in thin films of 1,3-diphenylisobenzofuran. J Am Chem Soc 2014; 136:7363-73. [PMID: 24735403 DOI: 10.1021/ja501337b] [Citation(s) in RCA: 112] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
In order to elucidate the mechanism of singlet fission in thin films of 1,3-diphenylisobenzofuran (1) we have performed ultrafast transient absorption spectroscopy as a function of sample temperature and excitation fluence on polycrystalline thin films composed of two polymorphs. Our earlier investigations revealed that films enriched in a particular polymorph of 1 displayed near 200% efficiency for triplet formation at 77 K, while films composed primarily of a second polymorph had a very low triplet quantum yield. Present data confirm the triplet yield disparities in the two polymorphs and demonstrate the distinct fates of the initially prepared singlets in films of different structure. Singlet fission is inhibited in the more stable polymorph due to rapid excimer formation and trapping. The less stable polymorph undergoes highly efficient singlet fission with a dominant time constant of 10-30 ps and without strong thermal activation. Transient absorption measurements with varying excitation fluence indicate that singlet-singlet annihilation is a primary competitor of singlet fission at higher fluence and that fission from higher-lying states can also contribute to the triplet formation process. Measurements employing different excitation energies and sample temperatures reveal the role that trapping processes play in attenuating the triplet quantum yield to produce the complex temperature dependence of the singlet fission yield. The rate constants for singlet fission itself are essentially temperature independent.
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Affiliation(s)
- Joel N Schrauben
- National Renewable Energy Laboratory, Golden, Colorado 80401, United States
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Piland GB, Burdett JJ, Hung TY, Chen PH, Lin CF, Chiu TL, Lee JH, Bardeen CJ. Dynamics of molecular excitons near a semiconductor surface studied by fluorescence quenching of polycrystalline tetracene on silicon. Chem Phys Lett 2014. [DOI: 10.1016/j.cplett.2014.03.075] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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