1
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Sturm F, Herok C, Fischer I. Non-Radiative Deactivation in Isolated Quinoline. J Phys Chem A 2024; 128:8421-8427. [PMID: 39303210 DOI: 10.1021/acs.jpca.4c04208] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/22/2024]
Abstract
The photophysics of the S2 1(ππ*) state of the polycyclic aromatic nitrogen-containing hydrocarbon (PANH) quinoline is investigated in a free jet using a picosecond laser system. A [1 + 1] multiphoton ionization spectrum yields the S2 origin at around 32 200 cm-1 and reveals several vibronic bands. In time-resolved experiments, quinoline is then excited between 312.2 and 279.7 nm. Probe wavelengths of 351 and 263.5 nm are employed. The dynamics is monitored by time-resolved photoelectron imaging. The images reveal a short-lived band at high electron kinetic energies with a ps lifetime and a band at lower electron kinetic energies that shows an offset at long delay times. In comparison with previous work, the offset is assigned to ionization from the T1 state. Lifetimes decrease from 45 ps at the S2 origin to 11 ps at +3550 cm-1. Most likely, the S2 1(ππ*) state deactivates by internal conversion to the S1 1(nπ*) state, followed by intersystem crossing to the triplet manifold.
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Affiliation(s)
- Floriane Sturm
- Institute of Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Christoph Herok
- Institute of Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Ingo Fischer
- Institute of Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
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2
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Wang L, Zhu R, Pu R, Liu W, Lu Y, Weng TC. Pressure-Promoted Triplet-Pair Separation in Singlet-Fission TIPS-Pentacene Nanofilms Revealed by Ultrafast Spectroscopy. NANOMATERIALS (BASEL, SWITZERLAND) 2024; 14:1487. [PMID: 39330644 PMCID: PMC11434892 DOI: 10.3390/nano14181487] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2024] [Revised: 07/05/2024] [Accepted: 07/15/2024] [Indexed: 09/28/2024]
Abstract
Singlet fission (SF), as an effective way to break through the Shockley-Queisser limit, can dramatically improve energy conversion efficiency in solar cell areas. The formation, separation, and relaxation of triplet-pair excitons directly affect the triplet yield, especially triplet-pair separation; thus, how to enhance the triplet-pair separation rate becomes one of the key points to improve SF efficiency; the decay mechanism where the singlet state is converted into two triplet states is significant for the study of the SF mechanism. Herein, we employ ultrafast transient absorption spectroscopy to study the singlet-fission process of nano-amorphous 6, 13-bis(triisopropylsilylethynyl)-Pentacene (TIPS-pentacene) films in a diamond anvil cell (DAC). A kinetics model related to the structural geometric details, as well as an evaluation of the pressure manipulation impacts, is demonstrated based on the experimental results. The results indicate that pressure manipulation enhanced the triplet-pair separation rates of SF-based materials according to their structural micro-environmental improvement when compressed in DAC, while the triplet-exciton transportation lifetime is prolonged. This work shows that pressure may effectively optimize the structural disorder of SF materials, which were found to improve triplet-pair separation efficiency and potentially offer an effective way to further improve SF efficiency.
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Affiliation(s)
- Lu Wang
- School of Physical Science and Technology, Shanghai Tech University, Shanghai 201210, China
| | - Ruixue Zhu
- Center for Transformative Science, Shanghai Tech University, Shanghai 201210, China
| | - Ruihua Pu
- School of Physical Science and Technology, Shanghai Tech University, Shanghai 201210, China
| | - Weimin Liu
- School of Physical Science and Technology, Shanghai Tech University, Shanghai 201210, China
| | - Yang Lu
- Center for High Pressure Science & Technology Advanced Research, Shanghai 201203, China
- Shanghai Key Laboratory of Material Frontiers Research in Extreme Environments (MFree), Shanghai Advanced Research in Physical Sciences (SHARPS), Shanghai 201203, China
| | - Tsu-Chieu Weng
- School of Physical Science and Technology, Shanghai Tech University, Shanghai 201210, China
- Center for Transformative Science, Shanghai Tech University, Shanghai 201210, China
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3
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Schulz T, Marian CM. Simulating the full spin manifold of triplet-pair states in a series of covalently linked TIPS-pentacenes. J Comput Chem 2024. [PMID: 39139132 DOI: 10.1002/jcc.27475] [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: 05/03/2024] [Revised: 07/17/2024] [Accepted: 07/24/2024] [Indexed: 08/15/2024]
Abstract
Combined density functional theory and multireference configuration interaction methods have been used to elucidate singlet fission (SF) pathways and mechanisms in three regioisomers of side-on linked pentacene dimers. In addition to the optically bright singlets (S1 $$ {}_1 $$ and S2 $$ {}_2 $$ ) and singly excited triplets (T1 $$ {}_1 $$ and T2 $$ {}_2 $$ ), the full spin manifold of multiexcitonic triplet-pair states (1 $$ {}^1 $$ ME,3 $$ {}^3 $$ ME,5 $$ {}^5 $$ ME) has been considered. In the ortho- and para-regioisomers, the1 $$ {}^1 $$ ME and S1 $$ {}_1 $$ potentials intersect upon geometry relaxation of the S1 $$ {}_1 $$ excitation. In the meta-regioisomer, the crossing occurs upon delocalization of the optically bright excitation. The energetic accessibility of these conical intersections and the absence of low-lying charge-transfer states suggests a direct SF mechanism, assisted by charge-resonance effects in the1 $$ {}^1 $$ ME state. While the5 $$ {}^5 $$ ME state does not appear to play a role in the SF mechanism of the ortho- and para-regioisomers, its participation in the disentanglement of the triplet pair is conceivable in the meta-regioisomer.
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Affiliation(s)
- Timo Schulz
- Institute of Theoretical and Computational Chemistry, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Christel M Marian
- Institute of Theoretical and Computational Chemistry, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
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4
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Kefer O, Kolesnichenko PV, Buckup T. Two-dimensional coherent electronic spectrometer with switchable multi-color configurations. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2024; 95:023003. [PMID: 38416044 DOI: 10.1063/5.0186915] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Accepted: 02/05/2024] [Indexed: 02/29/2024]
Abstract
Broadband implementation of two-dimensional electronic spectroscopy (2DES) is a desirable goal for numerous research groups, yet achieving it presents considerable challenges. An effective strategy to mitigate these challenges is the utilization of two-color approaches, effectively broadening the spectral bandwidth accessible with 2DES. Here, we present a simple approach to include multi-color configurations based on adjustable mirror mounts. This enables seamless toggling between single-color, two-color, and transient 2DES within the same spectroscopic apparatus, which is benchmarked on two common laser dyes, Rhodamine 6G and Nile blue. Upon mixing the dyes, single-color 2DES shows overlapping signals, whereas a high selectivity toward Nile blue responses is maintained in two-color and transient 2DES, owing to the fully resonant excitation that is spectrally shifted relative to the detection window. This method is readily implemented in other setups with similar experimental layouts and can be used as a simple solution to overcome existing bandwidth limitations. With the inclusion of transient 2DES, additional insights into excited-state processes can be gained due to its increased sensitivity toward excited-state coherences.
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Affiliation(s)
- Oskar Kefer
- Physikalisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, D-69120 Heidelberg, Germany
| | - Pavel V Kolesnichenko
- Physikalisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, D-69120 Heidelberg, Germany
| | - Tiago Buckup
- Physikalisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, D-69120 Heidelberg, Germany
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5
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Ye L, Zhao Y, Xu R, Li S, Zhang C, Li H, Zhu H. Above 100% Efficiency Photocharge Generation in Monolayer Semiconductors by Singlet Fission Sensitization. J Am Chem Soc 2023; 145:26257-26265. [PMID: 37994880 DOI: 10.1021/jacs.3c09119] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2023]
Abstract
Sensitizing inorganic semiconductors using singlet fission (SF) materials, which produce two excitons from one absorbed photon, can potentially boost their light-to-electricity conversion efficiency. The SF sensitization is particularly exciting for two-dimensional (2D) layered semiconductors with atomically flat surface and high carrier mobility but limited light absorption. However, efficiently harnessing triplet excitons from SF by charge transfer at organic/inorganic interface has been challenging, and the intricate interplay among competing processes remains unresolved. Here, we investigate SF sensitization in high-quality organic/2D bilayer heterostructures featuring TIPS-Pc single crystals. Through transient magneto-optical spectroscopy, we demonstrate that despite an ultrafast SF process in sub-100 fs, a significant fraction of singlet excitons in TIPS-Pc dissociate at the interface before fission, while triplet excitons from SF undergo diffusion-limited charge transfer at the interface in ∼10 ps to ns. Remarkably, the photocharge generation efficiency reaches 126% in heterostructures with optimal thickness, resulting from the competitive interplay between singlet exciton fission, dissociation, and triplet exciton transport. This presents a promising strategy for advancing SF-enhanced 2D optoelectronics beyond the conventional limits.
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Affiliation(s)
- Lei Ye
- Key Laboratory of Excited-State Materials of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou 310058, China
- ZJU-Hangzhou Global Scientific and Technological Innovation Center, Hangzhou 311215, China
| | - Yujie Zhao
- MOE Key Laboratory of Macromolecular Synthesis and Functionalization, International Research Center for X Polymers, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310058, China
| | - Rong Xu
- National Laboratory of Solid State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210046, China
| | - Shuangshuang Li
- Key Laboratory of Excited-State Materials of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou 310058, China
- ZJU-Hangzhou Global Scientific and Technological Innovation Center, Hangzhou 311215, China
| | - Chunfeng Zhang
- National Laboratory of Solid State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210046, China
| | - Hanying Li
- MOE Key Laboratory of Macromolecular Synthesis and Functionalization, International Research Center for X Polymers, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310058, China
| | - Haiming Zhu
- Key Laboratory of Excited-State Materials of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou 310058, China
- ZJU-Hangzhou Global Scientific and Technological Innovation Center, Hangzhou 311215, China
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6
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Kefer O, Ahrens L, Han J, Wollscheid N, Misselwitz E, Rominger F, Freudenberg J, Dreuw A, Bunz UHF, Buckup T. Efficient Intramolecular Singlet Fission in Spiro-Linked Heterodimers. J Am Chem Soc 2023; 145:17965-17974. [PMID: 37535495 DOI: 10.1021/jacs.3c05518] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/05/2023]
Abstract
We investigate intramolecular singlet fission (iSF) of spiro-linked azaacene heterodimers by time-resolved spectroscopy and quantum chemical calculations. Combining two different azaacenes through a nonconjugated linker using condensation chemistry furnishes azaacene heterodimers. Compared to their homodimers, iSF quantum yields are improved at an extended absorption range. The driving force of iSF, the energy difference ΔEiSF between the S1 state and the correlated triplet pair 1(TT), is tuned by the nature of the heterodimers. iSF is exothermic in all of the herein studied molecules. The overall quantum yield for triplet exciton formation reaches approximately 174%. This novel concept exploits large energy differences between singlet electronic states in combination with spatially fixed chromophores, which achieves efficient heterogeneous iSF, if the through-space interaction between the chromophores is minimal.
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Affiliation(s)
- Oskar Kefer
- Physikalisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, D-69120 Heidelberg, Germany
- Centre for Advanced Materials, Ruprecht-Karls-Universität Heidelberg, D-69120 Heidelberg, Germany
| | - Lukas Ahrens
- Organisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, D-69120 Heidelberg, Germany
| | - Jie Han
- Centre for Advanced Materials, Ruprecht-Karls-Universität Heidelberg, D-69120 Heidelberg, Germany
- Interdisziplinäres Zentrum für Wissenschaftliches Rechnen, Ruprecht-Karls-Universität Heidelberg, D-69120 Heidelberg, Germany
| | - Nikolaus Wollscheid
- Physikalisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, D-69120 Heidelberg, Germany
- Centre for Advanced Materials, Ruprecht-Karls-Universität Heidelberg, D-69120 Heidelberg, Germany
| | - Erik Misselwitz
- Organisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, D-69120 Heidelberg, Germany
| | - Frank Rominger
- Organisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, D-69120 Heidelberg, Germany
| | - Jan Freudenberg
- Organisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, D-69120 Heidelberg, Germany
| | - Andreas Dreuw
- Centre for Advanced Materials, Ruprecht-Karls-Universität Heidelberg, D-69120 Heidelberg, Germany
- Interdisziplinäres Zentrum für Wissenschaftliches Rechnen, Ruprecht-Karls-Universität Heidelberg, D-69120 Heidelberg, Germany
| | - Uwe H F Bunz
- Centre for Advanced Materials, Ruprecht-Karls-Universität Heidelberg, D-69120 Heidelberg, Germany
- Organisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, D-69120 Heidelberg, Germany
| | - Tiago Buckup
- Physikalisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, D-69120 Heidelberg, Germany
- Centre for Advanced Materials, Ruprecht-Karls-Universität Heidelberg, D-69120 Heidelberg, Germany
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7
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Tonami T, Nakano M, Kishi R, Kitagawa Y. Effects of introducing nitrogen atoms into oligoacene skeleton on vibronic coupling and singlet fission dynamics. Chem Phys Lett 2023. [DOI: 10.1016/j.cplett.2023.140311] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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8
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Bai Y, Ni W, Sun K, Chen L, Ma L, Zhao Y, Gurzadyan GG, Gelin MF. Plenty of Room on the Top: Pathways and Spectroscopic Signatures of Singlet Fission from Upper Singlet States. J Phys Chem Lett 2022; 13:11086-11094. [PMID: 36417755 DOI: 10.1021/acs.jpclett.2c03053] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
We investigate dynamic signatures of the singlet fission (SF) process triggered by the excitation of a molecular system to an upper singlet state SN (N > 1) and develop a computational methodology for the simulation of nonlinear spectroscopic signals revealing the SN → TT1 SF in real time. We demonstrate that SF can proceed directly from the upper state SN, bypassing the lowest excited state, S1. We determine the main SN → TT1 reaction pathways and show by computer simulation and spectroscopic measurements that the SN-initiated SF can be faster and more efficient than the traditionally studied S1 → TT1 SF. We claim that the SN → TT1 SF offers novel promising opportunities for engineering SF systems and enhancing SF yields.
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Affiliation(s)
- Yiting Bai
- School of Sciences, Hangzhou Dianzi University, Hangzhou 310018, China
| | - Wenjun Ni
- School of Sciences, Hangzhou Dianzi University, Hangzhou 310018, China
| | - Kewei Sun
- School of Sciences, Hangzhou Dianzi University, Hangzhou 310018, China
| | | | - Lin Ma
- School of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangdong 510006, China
| | - Yang Zhao
- School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
| | - Gagik G Gurzadyan
- State Key Laboratory of Fine Chemicals, Institute of Artificial Photosynthesis, Dalian University of Technology, Dalian 116024, China
| | - Maxim F Gelin
- School of Sciences, Hangzhou Dianzi University, Hangzhou 310018, China
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9
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Huang LY, Ai Q, Risko C. The Role of Crystal Packing on the Optical Response of Trialkyltetrelethynyl Acenes. J Chem Phys 2022; 157:084703. [DOI: 10.1063/5.0097421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The electronic and optical responses of an organic semiconductor (OSC) are dictated by the chemistries of the molecular or polymer building blocks and how these chromophores pack in the solid state. Understanding the physicochemical natures of these responses are not only critical for determining OSC performance for a particular application, but the UV/visible optical response may also be of potential use to determine aspects of the molecular-scale solid-state packing for crystal polymorphs or thin-film morphologies that are difficult to determine otherwise. To probe these relationships, we report the quantum-chemical investigation of a series of trialkyltetrelethynyl acenes (tetrel = silicon or germanium) that adopt the brickwork (BW), slip-stack (SS), or herringbone (HB) packing configurations; the π-conjugated backbones considered here are pentacene (PEN) and anthradithiophene (ADT). For comparison, HB-packed (unsubstituted) pentacene is also included. Density functional theory (DFT) and G0W0 (single-shot GW) electronic band structures, G0W0-BSE (Bethe-Salpeter Equation)-derived optical spectra, polarized ϵ2 spectra, and distributions of both singlet and triplet exciton wave functions are reported. Configurational disorder is also considered. Further, we evaluate the probability of singlet fission in these materials through energy conservation relationships.
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Affiliation(s)
| | - Qianxiang Ai
- Chemistry, Fordham University - Rose Hill Campus, United States of America
| | - Chad Risko
- Chemistry, University of Kentucky, United States of America
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10
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Mathew CM, Varghese A, Sugunan SK, Thomas VI. Rapid Computational Approach Towards Designing Singlet-Fission Chromophores by Tuning the Diradical Character of Heteroatom-Doped Polycyclic Aromatic Hydrocarbons Using the Atom-Specific Fukui Function. J Phys Chem A 2022; 126:1579-1590. [PMID: 35258970 DOI: 10.1021/acs.jpca.1c08094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Singlet fission (SF) is proposed as a promising method to circumvent the Shockley-Queisser threshold of single junction photovoltaics. Progress towards realizing efficient SF-based devices has been impeded by the fact that only a handful of molecules and their derivatives practically exhibit efficient SF. In the present work, we demonstrate a TDDFT-based rapid and cost-effective computational approach for designing SF chromophores by doping various atomic sites (substituting carbon atoms) of polycyclic aromatic hydrocarbons with nitrogen, phosphorus, and silicon. We establish a hitherto unexplored, direct correlation between the atom-specific chemical reactivity parameter─Fukui function─of these molecules with their frontier molecular orbital energies, diradical characters, and vertical singlet and triplet excitation energies. These quantitative correlations show exactly opposite trends for nitrogen-doped molecules and phosphorus- or silicon-doped molecules. The doped derivatives that have the Fukui function falling in a range of 0.03-0.14 possess the required intermediate diradical character and suitable singlet-triplet energies to qualify for SF candidature. Our findings enable one, at reasonable computational times and cost, to easily assess the doping criteria and to develop design rules for SF molecules in particular and for diradicaloids in general.
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Affiliation(s)
- Christina Mariam Mathew
- Department of Chemistry, CMS College Kottayam (Autonomous) (Mahatma Gandhi University), Kottayam 686001, Kerala, India.,Department of Chemistry, Baselius College Kottayam (Mahatma Gandhi University), Kottayam 686001, Kerala, India
| | - Ann Varghese
- Department of Chemistry, CMS College Kottayam (Autonomous) (Mahatma Gandhi University), Kottayam 686001, Kerala, India
| | - Sunish K Sugunan
- Department of Chemistry, CMS College Kottayam (Autonomous) (Mahatma Gandhi University), Kottayam 686001, Kerala, India
| | - Vibin Ipe Thomas
- Department of Chemistry, CMS College Kottayam (Autonomous) (Mahatma Gandhi University), Kottayam 686001, Kerala, India.,Institute for Integrated Programmes and Research in Basic Sciences (IIRBS), Mahatma Gandhi University, Priyadarshini Hills, Kottayam 686560, Kerala, India
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11
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Abstract
Singlet fission (SF) is a photophysical downconversion pathway, in which a singlet excitation transforms into two triplet excited states. As such, it constitutes an exciton multiplication generation process, which is currently at the focal point for future integration into solar energy conversion devices. Beyond this, various other exciting applications were proposed, including quantum cryptography or organic light emitting diodes. Also, the mechanistic understanding evolved rapidly during the last year. Unfortunately, the number of suitable SF-chromophores is still limited. This is per se problematic, considering the wide range of envisaged applicability. With that in mind, we emphasize uncommon SF-scaffolds and outline requirements as well as strategies to expand the chromophore pool of SF-materials.
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Affiliation(s)
- Tobias Ullrich
- Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg, Department für Chemie und Pharmazie, Egerlandstr. 1-3, 91058 Erlangen, Germany.
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12
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Wollscheid N, Lustres JLP, Brosius V, Motzkus M, Bunz UHF, Buckup T. Diffusion-Controlled Singlet Fission in a Chlorinated Phenazinothiadiazole by Broadband Femtosecond Transient Absorption. J Phys Chem B 2020; 124:10186-10194. [PMID: 33118824 DOI: 10.1021/acs.jpcb.0c05056] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Singlet fission (SF) is a process by which one excited singlet state yields two triplet states upon close interaction with a ground-state chromophore of the same kind. This photoreaction was first observed in solid state and has important implications in organic photovoltaics. Singlet fission was also reported in concentrated solutions, where the need for diffusion of the reaction partners slows the dynamics. This helps to single out reaction stages and to identify the involved species. In this work, ultrafast transient absorption spectroscopy and time-correlated single photon counting are applied to the concentration-dependent (from 10-1 to 102 mM) photodynamics of a tetrachlorinated phenazinothiadiazole in toluene. Time-resolved emission shows a monoexponential decay, which is constant across the emission band. The corresponding decay rate depends linearly on the concentration of the phenazinothiadiazole. Femtosecond transient absorption demonstrates that a concentration-dependent singlet-to-triplet conversion hides behind the emission decay which is diffusion controlled. Contrary to previous reports on SF in pentacenes and tetracenes, no indication of intermediate states has been found. Efficient, direct and barrierless SF is concluded. The strong enhancement of the triplet yield at increasingly higher concentrations of the thiadiazole indicates very efficient singlet fission with a triplet yield up to 189 ± 5%.
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Affiliation(s)
- Nikolaus Wollscheid
- Physikalisch-Chemisches Institut, Ruprecht-Karls Universität, D-69120 Heidelberg, Germany.,Centre for Advanced Materials, Ruprecht-Karls Universität, D-69120 Heidelberg, Germany
| | - Jose Luis Pérez Lustres
- Physikalisch-Chemisches Institut, Ruprecht-Karls Universität, D-69120 Heidelberg, Germany.,Centre for Advanced Materials, Ruprecht-Karls Universität, D-69120 Heidelberg, Germany
| | - Victor Brosius
- Centre for Advanced Materials, Ruprecht-Karls Universität, D-69120 Heidelberg, Germany.,Organisch-Chemisches Institut, Ruprecht-Karls Universität, D-69120 Heidelberg, Germany
| | - Marcus Motzkus
- Physikalisch-Chemisches Institut, Ruprecht-Karls Universität, D-69120 Heidelberg, Germany.,Centre for Advanced Materials, Ruprecht-Karls Universität, D-69120 Heidelberg, Germany
| | - Uwe H F Bunz
- Centre for Advanced Materials, Ruprecht-Karls Universität, D-69120 Heidelberg, Germany.,Organisch-Chemisches Institut, Ruprecht-Karls Universität, D-69120 Heidelberg, Germany
| | - Tiago Buckup
- Physikalisch-Chemisches Institut, Ruprecht-Karls Universität, D-69120 Heidelberg, Germany.,Centre for Advanced Materials, Ruprecht-Karls Universität, D-69120 Heidelberg, Germany
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13
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Alagna N, Lustres JLP, Roozbeh A, Han J, Hahn S, Berger FJ, Zaumseil J, Dreuw A, Bunz UHF, Buckup T. Ultrafast Singlet Fission in Rigid Azaarene Dimers with Negligible Orbital Overlap. J Phys Chem B 2020; 124:9163-9174. [DOI: 10.1021/acs.jpcb.0c07096] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Nicolò Alagna
- Physikalisch Chemisches Institut, Universität Heidelberg, D-69120 Heidelberg, Germany
- Centre for Advanced Materials, Universität Heidelberg, D-69120 Heidelberg, Germany
| | - Jose Luis Pérez Lustres
- Physikalisch Chemisches Institut, Universität Heidelberg, D-69120 Heidelberg, Germany
- Centre for Advanced Materials, Universität Heidelberg, D-69120 Heidelberg, Germany
| | - Ashkan Roozbeh
- Physikalisch Chemisches Institut, Universität Heidelberg, D-69120 Heidelberg, Germany
- Centre for Advanced Materials, Universität Heidelberg, D-69120 Heidelberg, Germany
| | - Jie Han
- Interdisziplinäres Zentrum für Wissenschaftliches Rechnen, Universität Heidelberg, D-69120 Heidelberg, Germany
- Centre for Advanced Materials, Universität Heidelberg, D-69120 Heidelberg, Germany
| | - Sebastian Hahn
- Organisch Chemisches Institut, Universität Heidelberg, D-69120 Heidelberg, Germany
| | - Felix J. Berger
- Physikalisch Chemisches Institut, Universität Heidelberg, D-69120 Heidelberg, Germany
- Centre for Advanced Materials, Universität Heidelberg, D-69120 Heidelberg, Germany
| | - Jana Zaumseil
- Physikalisch Chemisches Institut, Universität Heidelberg, D-69120 Heidelberg, Germany
- Centre for Advanced Materials, Universität Heidelberg, D-69120 Heidelberg, Germany
| | - Andreas Dreuw
- Interdisziplinäres Zentrum für Wissenschaftliches Rechnen, Universität Heidelberg, D-69120 Heidelberg, Germany
- Centre for Advanced Materials, Universität Heidelberg, D-69120 Heidelberg, Germany
| | - Uwe H. F. Bunz
- Organisch Chemisches Institut, Universität Heidelberg, D-69120 Heidelberg, Germany
- Centre for Advanced Materials, Universität Heidelberg, D-69120 Heidelberg, Germany
| | - Tiago Buckup
- Physikalisch Chemisches Institut, Universität Heidelberg, D-69120 Heidelberg, Germany
- Centre for Advanced Materials, Universität Heidelberg, D-69120 Heidelberg, Germany
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14
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Han J, Rehn DR, Buckup T, Dreuw A. Evaluation of Single-Reference DFT-Based Approaches for the Calculation of Spectroscopic Signatures of Excited States Involved in Singlet Fission. J Phys Chem A 2020; 124:8446-8460. [DOI: 10.1021/acs.jpca.0c07236] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Affiliation(s)
- Jie Han
- Interdisziplinäres Zentrum für Wissenschaftliches Rechnen, Universität Heidelberg, D-69120 Heidelberg, Germany
| | - Dirk Robert Rehn
- Interdisziplinäres Zentrum für Wissenschaftliches Rechnen, Universität Heidelberg, D-69120 Heidelberg, Germany
| | - Tiago Buckup
- Physikalisch Chemisches Institut, Universität Heidelberg, D-69120 Heidelberg, Germany
- Centre for Advanced Materials, Universität Heidelberg, D-69120 Heidelberg, Germany
| | - Andreas Dreuw
- Interdisziplinäres Zentrum für Wissenschaftliches Rechnen, Universität Heidelberg, D-69120 Heidelberg, Germany
- Centre for Advanced Materials, Universität Heidelberg, D-69120 Heidelberg, Germany
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15
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Wollscheid N, Günther B, Rao VJ, Berger FJ, Lustres JLP, Motzkus M, Zaumseil J, Gade LH, Höfener S, Buckup T. Ultrafast Singlet Fission and Intersystem Crossing in Halogenated Tetraazaperopyrenes. J Phys Chem A 2020; 124:7857-7868. [DOI: 10.1021/acs.jpca.0c04852] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Nikolaus Wollscheid
- Physikalisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 229, D-69120 Heidelberg, Germany
- Centre for Advanced Materials, Universität Heidelberg, Im Neuenheimer Feld 225, D-69120 Heidelberg, Germany
| | - Benjamin Günther
- Anorganisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 270, D-69120 Heidelberg, Germany
| | - Vaishnavi J. Rao
- Physikalisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 229, D-69120 Heidelberg, Germany
- Centre for Advanced Materials, Universität Heidelberg, Im Neuenheimer Feld 225, D-69120 Heidelberg, Germany
| | - Felix J. Berger
- Physikalisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 229, D-69120 Heidelberg, Germany
- Centre for Advanced Materials, Universität Heidelberg, Im Neuenheimer Feld 225, D-69120 Heidelberg, Germany
| | - J. Luis Pérez Lustres
- Physikalisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 229, D-69120 Heidelberg, Germany
- Centre for Advanced Materials, Universität Heidelberg, Im Neuenheimer Feld 225, D-69120 Heidelberg, Germany
| | - Marcus Motzkus
- Physikalisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 229, D-69120 Heidelberg, Germany
- Centre for Advanced Materials, Universität Heidelberg, Im Neuenheimer Feld 225, D-69120 Heidelberg, Germany
| | - Jana Zaumseil
- Physikalisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 229, D-69120 Heidelberg, Germany
- Centre for Advanced Materials, Universität Heidelberg, Im Neuenheimer Feld 225, D-69120 Heidelberg, Germany
| | - Lutz H. Gade
- Anorganisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 270, D-69120 Heidelberg, Germany
| | - Sebastian Höfener
- Institute of Physical Chemistry, Karlsruhe Institute of Technology (KIT), P.O. Box 6980, D-76131 Karlsruhe, Germany
| | - Tiago Buckup
- Physikalisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 229, D-69120 Heidelberg, Germany
- Centre for Advanced Materials, Universität Heidelberg, Im Neuenheimer Feld 225, D-69120 Heidelberg, Germany
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16
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Sardar S. Effects of site-specific substitution to hexacene and its effect towards singlet fission. J Mol Graph Model 2020; 98:107608. [DOI: 10.1016/j.jmgm.2020.107608] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2019] [Revised: 03/25/2020] [Accepted: 03/25/2020] [Indexed: 01/08/2023]
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17
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Kwang SY, Frontiera RR. Spatially Offset Femtosecond Stimulated Raman Spectroscopy: Observing Exciton Transport through a Vibrational Lens. J Phys Chem Lett 2020; 11:4337-4344. [PMID: 32427490 DOI: 10.1021/acs.jpclett.0c01114] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
To design better molecular electronic devices, we need a strong understanding of how charges or excitons propagate, as many efficiency losses arise during transport. Exciton transport has been difficult to study because excitons tend to be short-lived, have short diffusion lengths, and can easily recombine. Here, we debut spatially offset femtosecond stimulated Raman spectroscopy (SO-FSRS), a three-pulse ultrafast microscopy technique. By offsetting the photoexcitation beam, we can monitor Raman spectral changes as a function of both time and position. We used SO-FSRS on 6,13-bis(triisopropylsilylethynyl) pentacene, a well-studied organic semiconductor used in photovoltaics and field-effect transistors. We demonstrated that the fast exciton and free charge carrier transport axes are identical and observed that exciton transport is less anisotropic by a factor of ∼3. SO-FSRS is the first technique that directly tracks molecular structural evolution during exciton transport, which can provide roadmaps for tailor-making molecules for specific electronic devices.
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Affiliation(s)
- Siu Yi Kwang
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Renee R Frontiera
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
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18
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The Photophysical Properties of Triisopropylsilyl-ethynylpentacene—A Molecule with an Unusually Large Singlet-Triplet Energy Gap—In Solution and Solid Phases. CHEMISTRY-SWITZERLAND 2020. [DOI: 10.3390/chemistry2020033] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The process of singlet-exciton fission (SEF) has attracted much attention of late. One of the most popular SEF compounds is TIPS-pentacene (TIPS-P, where TIPS = triisopropylsilylethynyl) but, despite its extensive use as both a reference and building block, its photophysical properties are not so well established. In particular, the triplet state excitation energy remains uncertain. Here, we report quantitative data and spectral characterization for excited-singlet and -triplet states in dilute solution. The triplet energy is determined to be 7940 ± 1200 cm−1 on the basis of sensitization studies using time-resolved photoacoustic calorimetry. The triplet quantum yield at the limit of low concentration and low laser intensity is only ca. 1%. Self-quenching occurs at high solute concentration where the fluorescence yield and lifetime decrease markedly relative to dilute solution but we were unable to detect excimer emission by steady-state spectroscopy. Short-lived fluorescence, free from excimer emission or phosphorescence, occurs for crystals of TIPS-P, most likely from amorphous domains.
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19
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Zukun W, Wu R, Chen Z, Ye L, Li H, Zhu H. Ultrafast Electron Transfer Before Singlet Fission and Slow Triplet State Electron Transfer in Pentacene Single Crystal/C 60 Heterostructure. J Phys Chem A 2020; 124:4185-4192. [PMID: 32353232 DOI: 10.1021/acs.jpca.0c01791] [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 singlet fission (SF) process converts one high-energy singlet exciton to two low-energy triplet excitons after absorbing one photon. Organic photovoltaic devices based on the SF process have shown great potential in solar energy conversion to exceed Shockley-Queisser limit. The key to SF photovoltaic devices requires efficient electron transfer (ET) from triplet exciton after SF, which is yet to be thoroughly investigated. Here, we performed thorough photophysical studies in 6,13-Bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene)/C60 heterostructures using TIPS-pentacene microsize single crystal as a well-defined model system. We show the SF process in TIPS-pentacene single crystal occurs by a two-step process, with triplet pair intermediates forming in 75 fs and then dissociating to non-interacting triplets in 1.6 ps. The SF process in single crystal is comparable to that in polycrystalline film. Importantly, we observe a considerable fraction of singlet excitons is quenched by ultrafast (<75 fs) interfacial ET prior to fission and no ET from triplet excitons in 1.5 ns time window. We confirm that the absence of ET is not limited by exciton diffusion but due to very slow (≫1.5 ns) interfacial ET from triplet exciton. The observations contradict expected singlet and triplet ET behaviors based on a simple two-state Marcus ET model and suggest long-range interfacial ET from delocalized photoexcitation. The ultrafast ET from singlet exciton before SF and slow ET from triplet exciton call for reconsideration and careful design of efficient SF photovoltaic devices.
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Affiliation(s)
- Wang Zukun
- Centre for Chemistry of High-Performance & Novel Materials, Department of Chemistry, Zhejiang University, Hangzhou 310027, Zhejiang, China
| | - Ruihan Wu
- MOE Key Laboratory of Macromolecule Synthesis and Functionalization, State Key Laboratory of Silicon Materials, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027, P. R. China
| | - Zeng Chen
- Centre for Chemistry of High-Performance & Novel Materials, Department of Chemistry, Zhejiang University, Hangzhou 310027, Zhejiang, China
| | - Lei Ye
- Centre for Chemistry of High-Performance & Novel Materials, Department of Chemistry, Zhejiang University, Hangzhou 310027, Zhejiang, China
| | - Hanying Li
- MOE Key Laboratory of Macromolecule Synthesis and Functionalization, State Key Laboratory of Silicon Materials, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027, P. R. China
| | - Haiming Zhu
- Centre for Chemistry of High-Performance & Novel Materials, Department of Chemistry, Zhejiang University, Hangzhou 310027, Zhejiang, China
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20
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Matsuda S, Oyama S, Kobori Y. Electron spin polarization generated by transport of singlet and quintet multiexcitons to spin-correlated triplet pairs during singlet fissions. Chem Sci 2020; 11:2934-2942. [PMID: 34122794 PMCID: PMC8157521 DOI: 10.1039/c9sc04949e] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Singlet fission (SF) is expected to exceed the Shockley–Queisser theoretical limit of efficiency of organic solar cells. Transport of spin-entanglement in the triplet–triplet pair state via one singlet exciton is a promising phenomenon for several energy conversion applications including quantum information science. However, direct observation of electron spin polarization by transport of entangled spin-states has not been presented. In this study, time-resolved electron paramagnetic resonance has been utilized to observe the transportation of singlet and quintet characters generating correlated triplet–triplet (T + T) exciton-pair states by probing the electron spin polarization (ESP) generated in thin films of 6,13-bis(triisopropylsilylethynyl)pentacene. We have clearly demonstrated that the ESP detected at the resonance field positions of individual triplet excitons is dependent on the morphology and on the detection delay time after laser flash to cause SF. ESP was clearly explained by quantum superposition of singlet–triplet–quintet wavefunctions via picosecond triplet-exciton dissociation as the electron spin polarization transfer from strongly exchange-coupled singlet and quintet TT states to weakly-coupled spin-correlated triplet pair states. Although the coherent superposition of spin eigenstates was not directly detected, the present interpretation of the spin correlation of the separated T + T exciton pair may pave new avenues not only for elucidating the vibronic role in the de-coupling between two excitons but also for scalable quantum information processing using quick T + T dissociation via one-photon excitation. Singlet fission (SF) is expected to exceed the Shockley–Queisser theoretical limit of efficiency of organic solar cells.![]()
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Affiliation(s)
- Saki Matsuda
- Department of Chemistry, Graduate School of Science, Kobe University 1-1 Rokkodai-cho, Nada-ku Kobe 657-8501 Japan
| | - Shinya Oyama
- Department of Chemistry, Graduate School of Science, Kobe University 1-1 Rokkodai-cho, Nada-ku Kobe 657-8501 Japan
| | - Yasuhiro Kobori
- Department of Chemistry, Graduate School of Science, Kobe University 1-1 Rokkodai-cho, Nada-ku Kobe 657-8501 Japan .,Molecular Photoscience Research Center, Kobe University 1-1 Rokkodai-cho, Nada-ku Kobe 657-8501 Japan
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21
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Han J, Xie Q, Luo J, Deng GH, Qian Y, Sun D, Harutyunyan AR, Chen G, Rao Y. Anisotropic Geminate and Non-Geminate Recombination of Triplet Excitons in Singlet Fission of Single Crystalline Hexacene. J Phys Chem Lett 2020; 11:1261-1267. [PMID: 31971388 DOI: 10.1021/acs.jpclett.9b03800] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Singlet fission is believed to improve the efficiency of solar energy conversion by breaking up the Shockley-Queisser thermodynamic limit. Understanding of triplet excitons generated by singlet fission is essential for solar energy exploitation. Here we employed transient absorption microscopy to examine dynamical behaviors of triplet excitons. We observed anisotropic recombination of triplet excitons in hexacene single crystals. The triplet exciton relaxations from singlet fission proceed in both geminate and non-geminate recombination. For the geminate recombination, the different rates were attributed to the significant difference in their related energy change based on the Redfield quantum dissipation theory. The process is mainly governed by the electron-phonon interaction in hexacene. On the other hand, the non-geminate recombination is of bimolecular origin through energy transfer. In the triplet-triplet bimolecular process, the rates along the two different optical axes in the a-b crystalline plane differ by a factor of 4. This anisotropy in the triplet-triplet recombination rates was attributed to the interference in the coupling probability of dipole-dipole interactions in the different geometric configurations of hexacene single crystals. Our experimental findings provide new insight into future design of singlet fission materials with desirable triplet exciton exploitations.
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Affiliation(s)
- Jian Han
- School of Chemical Engineering , Nanjing University of Science and Technology , Nanjing 210094 , China
- Department of Chemistry and Biochemistry , Utah State University , Logan , Utah 84322 , United States
| | - Qing Xie
- Department of Chemistry and Biochemistry , Utah State University , Logan , Utah 84322 , United States
| | - Jun Luo
- School of Chemical Engineering , Nanjing University of Science and Technology , Nanjing 210094 , China
| | - 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
| | - Dezheng Sun
- Department of Physics , Columbia University , New York , New York 10027 , United States
| | - Avetik R Harutyunyan
- Honda Research Institute, USA, Inc. , San Jose , California 95134 , United States
| | - Gugang Chen
- Honda Research Institute, USA, Inc. , San Jose , California 95134 , United States
| | - Yi Rao
- Department of Chemistry and Biochemistry , Utah State University , Logan , Utah 84322 , United States
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22
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Hudson RJ, de la Perrelle JM, Pensack RD, Kudisch B, Scholes GD, Huang DM, Kee TW. Organizing Crystalline Functionalized Pentacene Using Periodicity of Poly(Vinyl Alcohol). J Phys Chem Lett 2020; 11:516-523. [PMID: 31884794 DOI: 10.1021/acs.jpclett.9b03373] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Nanoparticles of acenes exhibit highly efficient intermolecular singlet fission (SF). Recent reports indicate that altering the morphology of 6,13-bis-(triisopropylsilylethynyl)pentacene (TIPS-Pn) nanoparticles has a profound influence on their SF dynamics. Here, we show that poly(vinyl alcohol) (PVA) induces a phase transition in preformed TIPS-Pn nanoparticles. These nanoparticles are amorphous when initially formed but crystalline after addition of PVA. Surface characterization indicates that a diffuse PVA layer surrounds the nanoparticles. We propose that a periodic interaction between the hydroxyl groups of PVA and TIPS groups of TIPS-Pn on the nanoparticle surface induces a large-scale structural rearrangement to yield crystalline TIPS-Pn. Such reorganization in preformed organic nanoparticles is unprecedented, and we believe that this is the first report of such an effect induced by polymer adsorption. Transient absorption spectroscopic results reveal that SF within these nanoparticles is accelerated by an order of magnitude upon structural rearrangement.
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Affiliation(s)
- Rohan J Hudson
- Department of Chemistry , The University of Adelaide , Adelaide , South Australia 5005 , Australia
| | - Jessica M de la Perrelle
- Department of Chemistry , The University of Adelaide , Adelaide , South Australia 5005 , Australia
| | - Ryan D Pensack
- Department of Chemistry , Princeton University , Princeton , New Jersey 08544 , United States
| | - Bryan Kudisch
- Department of Chemistry , Princeton University , Princeton , New Jersey 08544 , United States
| | - Gregory D Scholes
- Department of Chemistry , Princeton University , Princeton , New Jersey 08544 , United States
| | - David M Huang
- Department of Chemistry , The University of Adelaide , Adelaide , South Australia 5005 , Australia
| | - Tak W Kee
- Department of Chemistry , The University of Adelaide , Adelaide , South Australia 5005 , Australia
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23
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Mora‐Fuentes JP, Papadopoulos I, Thiel D, Álvarez‐Boto R, Cortizo‐Lacalle D, Clark T, Melle‐Franco M, Guldi DM, Mateo‐Alonso A. Singlet Fission in Pyrene‐Fused Azaacene Dimers. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.201911529] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Juan P. Mora‐Fuentes
- POLYMAT University of the Basque Country UPV/EHU Avenida de Tolosa 72 20018 Donostia-San Sebastian Spain
| | - Ilias Papadopoulos
- Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials Friedrich-Alexander-Universität Erlangen-Nürnberg Egerlandstr. 3 91058 Erlangen Germany
| | - Dominik Thiel
- Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials Friedrich-Alexander-Universität Erlangen-Nürnberg Egerlandstr. 3 91058 Erlangen Germany
| | - Roberto Álvarez‐Boto
- CICECO—Aveiro Institute of Materials Department of Chemistry University of Aveiro 3810-193 Aveiro Portugal
| | - Diego Cortizo‐Lacalle
- POLYMAT University of the Basque Country UPV/EHU Avenida de Tolosa 72 20018 Donostia-San Sebastian Spain
| | - Timothy Clark
- Computer-Chemistry Centre Department of Chemistry and Pharmacy Friedrich-Alexander-Universität Erlangen-Nürnberg Naegelsbachstr. 25 91052 Erlangen Germany
| | - Manuel Melle‐Franco
- CICECO—Aveiro Institute of Materials Department of Chemistry University of Aveiro 3810-193 Aveiro Portugal
| | - Dirk M. Guldi
- Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials Friedrich-Alexander-Universität Erlangen-Nürnberg Egerlandstr. 3 91058 Erlangen Germany
| | - Aurelio Mateo‐Alonso
- POLYMAT University of the Basque Country UPV/EHU Avenida de Tolosa 72 20018 Donostia-San Sebastian Spain
- Ikerbasque Basque Foundation for Science Bilbao Spain
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24
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Mora‐Fuentes JP, Papadopoulos I, Thiel D, Álvarez‐Boto R, Cortizo‐Lacalle D, Clark T, Melle‐Franco M, Guldi DM, Mateo‐Alonso A. Singlet Fission in Pyrene-Fused Azaacene Dimers. Angew Chem Int Ed Engl 2020; 59:1113-1117. [PMID: 31647593 PMCID: PMC7687256 DOI: 10.1002/anie.201911529] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Indexed: 02/02/2023]
Abstract
Singlet fission has emerged as a promising strategy to avoid the loss of extra energy through thermalization in solar cells. A family of dimers consisting of nitrogen-doped pyrene-fused acenes that undergo singlet fission with triplet quantum yields as high as 125 % are presented. They provide new perspectives for nitrogenated polycyclic aromatic hydrocarbons and for the design of new materials for singlet fission.
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Affiliation(s)
- Juan P. Mora‐Fuentes
- POLYMATUniversity of the Basque Country UPV/EHUAvenida de Tolosa 7220018Donostia-San SebastianSpain
| | - Ilias Papadopoulos
- Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular MaterialsFriedrich-Alexander-Universität Erlangen-NürnbergEgerlandstr. 391058ErlangenGermany
| | - Dominik Thiel
- Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular MaterialsFriedrich-Alexander-Universität Erlangen-NürnbergEgerlandstr. 391058ErlangenGermany
| | - Roberto Álvarez‐Boto
- CICECO—Aveiro Institute of MaterialsDepartment of ChemistryUniversity of Aveiro3810-193AveiroPortugal
| | - Diego Cortizo‐Lacalle
- POLYMATUniversity of the Basque Country UPV/EHUAvenida de Tolosa 7220018Donostia-San SebastianSpain
| | - Timothy Clark
- Computer-Chemistry CentreDepartment of Chemistry and PharmacyFriedrich-Alexander-Universität Erlangen-NürnbergNaegelsbachstr. 2591052ErlangenGermany
| | - Manuel Melle‐Franco
- CICECO—Aveiro Institute of MaterialsDepartment of ChemistryUniversity of Aveiro3810-193AveiroPortugal
| | - Dirk M. Guldi
- Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular MaterialsFriedrich-Alexander-Universität Erlangen-NürnbergEgerlandstr. 391058ErlangenGermany
| | - Aurelio Mateo‐Alonso
- POLYMATUniversity of the Basque Country UPV/EHUAvenida de Tolosa 7220018Donostia-San SebastianSpain
- IkerbasqueBasque Foundation for ScienceBilbaoSpain
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25
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Jones AC, Kearns NM, Ho JJ, Flach JT, Zanni MT. Impact of non-equilibrium molecular packings on singlet fission in microcrystals observed using 2D white-light microscopy. Nat Chem 2019; 12:40-47. [PMID: 31792384 DOI: 10.1038/s41557-019-0368-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Accepted: 10/08/2019] [Indexed: 11/09/2022]
Abstract
Singlet fission, the process of splitting a singlet exciton into two triplet excitons, has been proposed as a mechanism for improving the efficiency of future photovoltaic devices. In organic semiconductors exhibiting singlet fission, the geometric relationship between molecules plays an important role by setting the intermolecular couplings that determine the system energetics. Here, we spatially image TIPS-pentacene microcrystals using ultrafast two-dimensional white-light microscopy and discover a low-energy singlet state sparsely distributed throughout the microcrystals, with higher concentrations at edges and morphological defects. The spectra of these singlet states are consistent with slip-stacked molecular geometries and increased charge-transfer couplings. The picosecond-timescale kinetics of these low-energy singlet states matches that of the correlated triplet-pair state, which we attribute to singlet/triplet-pair interconversion at these sites. Our observations support the conclusion that small populations of geometries with favourable energetics can play outsized roles in singlet fission processes.
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Affiliation(s)
- Andrew C Jones
- Department of Chemistry, University of Wisconsin, Madison, WI, USA
| | | | - Jia-Jung Ho
- Department of Chemistry, University of Wisconsin, Madison, WI, USA
| | - Jessica T Flach
- Department of Chemistry, University of Wisconsin, Madison, WI, USA
| | - Martin T Zanni
- Department of Chemistry, University of Wisconsin, Madison, WI, USA.
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26
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Alagna N, Pérez Lustres JL, Wollscheid N, Luo Q, Han J, Dreuw A, Geyer FL, Brosius V, Bunz UHF, Buckup T, Motzkus M. Singlet Fission in Tetraaza-TIPS-Pentacene Oligomers: From fs Excitation to μs Triplet Decay via the Biexcitonic State. J Phys Chem B 2019; 123:10780-10793. [DOI: 10.1021/acs.jpcb.9b08031] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Nicolò Alagna
- Centre for Advanced Materials, University of Heidelberg, D-69120 Heidelberg, Germany
| | - J. Luis Pérez Lustres
- Centre for Advanced Materials, University of Heidelberg, D-69120 Heidelberg, Germany
| | - Nikolaus Wollscheid
- Centre for Advanced Materials, University of Heidelberg, D-69120 Heidelberg, Germany
| | | | | | - Andreas Dreuw
- Centre for Advanced Materials, University of Heidelberg, D-69120 Heidelberg, Germany
| | | | | | - Uwe H. F. Bunz
- Centre for Advanced Materials, University of Heidelberg, D-69120 Heidelberg, Germany
| | - Tiago Buckup
- Centre for Advanced Materials, University of Heidelberg, D-69120 Heidelberg, Germany
| | - Marcus Motzkus
- Centre for Advanced Materials, University of Heidelberg, D-69120 Heidelberg, Germany
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27
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Abstract
Singlet fission is the photoinduced conversion of a singlet exciton into two triplet states of half-energy. This multiplication mechanism has been successfully applied to improve the efficiency of single-junction solar cells in the visible spectral range. Here we show that singlet fission may also occur via a sequential mechanism, where the two triplet states are generated consecutively by exploiting oxygen as a catalyst. This sequential formation of carriers is demonstrated for two acene-like molecules in solution. First, energy transfer from the excited acene to triplet oxygen yields one triplet acene and singlet oxygen. In the second stage, singlet oxygen combines with a ground-state acene to complete singlet fission. This yields a second triplet molecule. The sequential mechanism accounts for approximately 40% of the triplet quantum yield in the studied molecules; this process occurs in dilute solutions and under atmospheric conditions, where the single-step SF mechanism is inactive.
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28
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Hoffmann M, Mewes SA, Wieland S, Popp C, Dreuw A. Electron-Hole Correlation as Unambiguous and Universal Classification for the Nature of Low-Lying ππ* States of Nitrogen Heterocycles. J Phys Chem Lett 2019; 10:6112-6117. [PMID: 31573203 DOI: 10.1021/acs.jpclett.9b02522] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The 1La and 1Lb classification of electronically excited states of cata-condensed hydrocarbons proposed by Platt in 1949 ( Platt , J. R. J. Chem. Phys. 1949 , 17 , 484 ) is challenged by investigating a series of N-heteronaphthalenes and comparison of their low-lying ππ* excited states to those of naphthalene. The breakdown of Platt's classification scheme for N-heterocycles is highlighted, and a reliable and versatile alternative using exciton analyses is presented. The strength of electron-hole correlation turns out to be the most reliable distinguishing feature, and thus, an alternative nomenclature of 1Lw (weakly correlated) and 1Ls (strongly correlated) is proposed. Furthermore, fundamental guidelines for their property modulation through N-atom substitution patterns are discussed.
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Affiliation(s)
- Marvin Hoffmann
- Interdisciplinary Center for Scientific Computing , Ruprecht-Karls University , Im Neuenheimer Feld 205A , D-69120 Heidelberg , Germany
| | - Stefanie A Mewes
- Centre for Theoretical Chemistry and Physics, New Zealand Institute for Advanced Studies , Massey University Albany , Private Bag 102904, Auckland 0632 , New Zealand
| | - Sonja Wieland
- Interdisciplinary Center for Scientific Computing , Ruprecht-Karls University , Im Neuenheimer Feld 205A , D-69120 Heidelberg , Germany
| | - Christoph Popp
- Interdisciplinary Center for Scientific Computing , Ruprecht-Karls University , Im Neuenheimer Feld 205A , D-69120 Heidelberg , Germany
| | - Andreas Dreuw
- Interdisciplinary Center for Scientific Computing , Ruprecht-Karls University , Im Neuenheimer Feld 205A , D-69120 Heidelberg , Germany
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29
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Fallon KJ, Budden P, Salvadori E, Ganose AM, Savory CN, Eyre L, Dowland S, Ai Q, Goodlett S, Risko C, Scanlon DO, Kay CWM, Rao A, Friend RH, Musser AJ, Bronstein H. Exploiting Excited-State Aromaticity To Design Highly Stable Singlet Fission Materials. J Am Chem Soc 2019; 141:13867-13876. [PMID: 31381323 DOI: 10.1021/jacs.9b06346] [Citation(s) in RCA: 68] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Singlet fission, the process of forming two triplet excitons from one singlet exciton, is a characteristic reserved for only a handful of organic molecules due to the atypical energetic requirement for low energy excited triplet states. The predominant strategy for achieving such a trait is by increasing ground state diradical character; however, this greatly reduces ambient stability. Herein, we exploit Baird's rule of excited state aromaticity to manipulate the singlet-triplet energy gap and create novel singlet fission candidates. We achieve this through the inclusion of a [4n] 5-membered heterocycle, whose electronic resonance promotes aromaticity in the triplet state, stabilizing its energy relative to the singlet excited state. Using this theory, we design a family of derivatives of indolonaphthyridine thiophene (INDT) with highly tunable excited state energies. Not only do we access novel singlet fission materials, they also exhibit excellent ambient stability, imparted due to the delocalized nature of the triplet excited state. Spin-coated films retained up to 85% activity after several weeks of exposure to oxygen and light, while analogous films of TIPS-pentacene showed full degradation after 4 days, showcasing the excellent stability of this class of singlet fission scaffold. Extension of our theoretical analysis to almost ten thousand candidates reveals an unprecedented degree of tunability and several thousand potential fission-capable candidates, while clearly demonstrating the relationship between triplet aromaticity and singlet-triplet energy gap, confirming this novel strategy for manipulating the exchange energy in organic materials.
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Affiliation(s)
- Kealan J Fallon
- Department of Chemistry , University of Cambridge , Cambridge CB2 1EW , U.K
| | - Peter Budden
- Cavendish Laboratory , University of Cambridge , Cambridge CB3 0HE , U.K
| | - Enrico Salvadori
- Department of Chemistry , University of Turin , Via Pietro Giuria 7 , 10125 Torino , Italy.,London Centre for Nanotechnology , University College London , 17-19 Gordon Street , London WC1H 0AH , U.K
| | - Alex M Ganose
- Kathleen Lonsdale Materials Chemistry, Department of Chemistry , University College London , 20 Gordon Street , London WC1H 0AJ , U.K.,Thomas Young Centre , University College London , Gower Street , London WC1E 6BT , U.K.,Diamond Light Source Ltd., Diamond House , Harwell Science and Innovation Campus , Oxfordshire OX11 0DE , U.K
| | - Christopher N Savory
- Kathleen Lonsdale Materials Chemistry, Department of Chemistry , University College London , 20 Gordon Street , London WC1H 0AJ , U.K.,Thomas Young Centre , University College London , Gower Street , London WC1E 6BT , U.K
| | - Lissa Eyre
- Cavendish Laboratory , University of Cambridge , Cambridge CB3 0HE , U.K
| | - Simon Dowland
- Cavendish Laboratory , University of Cambridge , Cambridge CB3 0HE , U.K
| | - Qianxiang Ai
- Department of Chemistry and Center for Applied Energy Research , University of Kentucky , Lexington , Kentucky 40506 , United States
| | - Stephen Goodlett
- Department of Chemistry and Center for Applied Energy Research , University of Kentucky , Lexington , Kentucky 40506 , United States
| | - Chad Risko
- Department of Chemistry and Center for Applied Energy Research , University of Kentucky , Lexington , Kentucky 40506 , United States
| | - David O Scanlon
- Kathleen Lonsdale Materials Chemistry, Department of Chemistry , University College London , 20 Gordon Street , London WC1H 0AJ , U.K.,Thomas Young Centre , University College London , Gower Street , London WC1E 6BT , U.K.,Diamond Light Source Ltd., Diamond House , Harwell Science and Innovation Campus , Oxfordshire OX11 0DE , U.K
| | - Christopher W M Kay
- London Centre for Nanotechnology , University College London , 17-19 Gordon Street , London WC1H 0AH , U.K.,Department of Chemistry , University of Saarland , 66123 Saarbrücken , Germany
| | - Akshay Rao
- Cavendish Laboratory , University of Cambridge , Cambridge CB3 0HE , U.K
| | - Richard H Friend
- Cavendish Laboratory , University of Cambridge , Cambridge CB3 0HE , U.K
| | - Andrew J Musser
- Department of Physics and Astronomy , University of Sheffield , Hicks Building, Hounsfield Road , Sheffield S3 7RH , U.K
| | - Hugo Bronstein
- Department of Chemistry , University of Cambridge , Cambridge CB2 1EW , U.K.,Cavendish Laboratory , University of Cambridge , Cambridge CB3 0HE , U.K
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30
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Abstract
Entanglement of states is one of the most surprising and counterintuitive consequences of quantum mechanics, with potent applications in cryptography and computing. In organic semiconductor materials, one particularly significant manifestation is the spin-entangled triplet-pair state, which consists of a pair of localized triplet excitons coupled into an overall spin-0, -1, or -2 configuration. The most widely analyzed of these is the spin-0 pair, denoted 1(TT), which was initially invoked in the 1960s to explain delayed fluorescence in acene films. It is considered an essential gateway state for triplet-triplet annihilation and the reverse process, singlet fission, enabling interconversion between one singlet and two triplet excitons without any change in overall spin. This state has returned to the forefront of organic materials research in recent years, thanks both to its central role in the resurgent field of singlet fission and to its implication in a host of exotic new photophysical behaviors. Here we review the properties of triplet-pair states, from first principles to recent experimental results.
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Affiliation(s)
- Andrew J Musser
- Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, United Kingdom; ,
| | - Jenny Clark
- Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, United Kingdom; ,
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31
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Alagna N, Han J, Wollscheid N, Perez Lustres JL, Herz J, Hahn S, Koser S, Paulus F, Bunz UHF, Dreuw A, Buckup T, Motzkus M. Tailoring Ultrafast Singlet Fission by the Chemical Modification of Phenazinothiadiazoles. J Am Chem Soc 2019; 141:8834-8845. [DOI: 10.1021/jacs.9b01079] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Nicolò Alagna
- Centre for Advanced Materials
, Im Neuenheimer Feld 225, D-69120 Heidelberg, Germany
| | | | - Nikolaus Wollscheid
- Centre for Advanced Materials
, Im Neuenheimer Feld 225, D-69120 Heidelberg, Germany
| | - J. Luis Perez Lustres
- Centre for Advanced Materials
, Im Neuenheimer Feld 225, D-69120 Heidelberg, Germany
| | | | | | | | | | - Uwe H. F. Bunz
- Centre for Advanced Materials
, Im Neuenheimer Feld 225, D-69120 Heidelberg, Germany
| | - Andreas Dreuw
- Centre for Advanced Materials
, Im Neuenheimer Feld 225, D-69120 Heidelberg, Germany
| | - Tiago Buckup
- Centre for Advanced Materials
, Im Neuenheimer Feld 225, D-69120 Heidelberg, Germany
| | - Marcus Motzkus
- Centre for Advanced Materials
, Im Neuenheimer Feld 225, D-69120 Heidelberg, Germany
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32
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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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33
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Alagna N, Han J, Herz J, Perez Lustres JL, Hahn S, Koser S, Geyer FL, Hahn S, Bunz U, Dreuw A, Buckup T, Motzkus M. Tailoring ultrafast singlet fission by structural modification of phenazinothiadiazoles. EPJ WEB OF CONFERENCES 2019. [DOI: 10.1051/epjconf/201920509013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Ultrafast transient absorption and quantum chemistry calculations are combined to demonstrate singlet fission in newly functionalized TIPS-Tetracenes. The coupling strength (but not the energy gap) between Si and ’(TT) states gauges singlet fission efficiency and rate.
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34
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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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35
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Abstract
Building efficient triplet-harvesting layers for photovoltaic applications requires a deep understanding of the microscopic properties of the components involved and their dynamics. Singlet fission is a particularly appealing mechanism as it generates two excitons from a single photon. However, the pathways of the coupled triplets into free species, and their dependence on the intermolecular geometry, has not been fully explored. In this work, we produce highly ordered dilute pentacene films with distinct parallel and herringbone dimers and aggregates. Using electron paramagnetic resonance spectroscopy, we provide compelling evidence for the formation of distinct quintet excitons in ambient conditions, with intrinsically distinctive electronic and kinetic properties. We find that the ability of quintets to separate into free triplets is promoted in the parallel dimers and this provides molecular design rules to control the triplets, favouring either enhanced photovoltaic efficiency (parallel) or strongly bound pairs that could be exploited for logic applications (herringbone). Singlet fission results in the formation of a pair of triplets, known as a quintet. Here, the authors identify long-lived quintets in dilute pentacene films at room temperature, with lifetimes influenced by intermolecular geometry having implications for the design of triplet-harvesting films.
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36
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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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37
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Thampi A, Stern HL, Cheminal A, Tayebjee MJY, Petty AJ, Anthony JE, Rao A. Elucidation of Excitation Energy Dependent Correlated Triplet Pair Formation Pathways in an Endothermic Singlet Fission System. J Am Chem Soc 2018; 140:4613-4622. [PMID: 29275626 DOI: 10.1021/jacs.7b06274] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Singlet fission is the spin-allowed conversion of a photogenerated singlet exciton into two triplet excitons in organic semiconductors, which could enable single-junction photovoltaic cells to break the Shockley-Queisser limit. The conversion of singlets to free triplets is mediated by an intermediate correlated triplet pair (TT) state, but an understanding of how the formation and dissociation of these states depend on energetics and morphology is lacking. In this study, we probe the dynamics of TT states in a model endothermic fission system, TIPS-Tc nanoparticles, which show a mixture of crystalline and disordered regions. We observe the formation of different TT states, with varying yield and different rates of singlet decay, depending on the excitation energy. An emissive TT state is observed to grow in over 1 ns when excited at 480 nm, in contrast to excitation at lower energies where this emissive TT state is not observed. This suggests that the pathway for singlet fission in these nanoparticles is strongly influenced by the initial sub-100 fs relaxation of the photoexcited state away from the Franck-Condon point, with multiple possible TT states. On nanosecond time scales, the TT states are converted to free triplets, which suggests that TT states might diffuse into the disordered regions of the nanoparticles where their breakup to free triplets is favored. The free triplets then decay on μs time scales, despite the confined nature of the system. Our results provide important insights into the mechanism of endothermic singlet fission and the design of nanostructures to harness singlet fission.
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Affiliation(s)
- Arya Thampi
- Cavendish Laboratory , University of Cambridge , Cambridge CB3 0HE , U.K
| | - Hannah L Stern
- Cavendish Laboratory , University of Cambridge , Cambridge CB3 0HE , U.K
| | - Alexandre Cheminal
- Cavendish Laboratory , University of Cambridge , Cambridge CB3 0HE , U.K
| | - Murad J Y Tayebjee
- Cavendish Laboratory , University of Cambridge , Cambridge CB3 0HE , U.K
| | - Anthony J Petty
- University of Kentucky , Lexington , Kentucky 40506 , United States
| | - John E Anthony
- University of Kentucky , Lexington , Kentucky 40506 , United States
| | - Akshay Rao
- Cavendish Laboratory , University of Cambridge , Cambridge CB3 0HE , U.K
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38
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Grieco C, Kennehan ER, Rimshaw A, Payne MM, Anthony JE, Asbury JB. Harnessing Molecular Vibrations to Probe Triplet Dynamics During Singlet Fission. J Phys Chem Lett 2017; 8:5700-5706. [PMID: 29112418 DOI: 10.1021/acs.jpclett.7b02434] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Ultrafast vibrational spectroscopy in the mid-infrared spectral range provides the opportunity to probe the dynamics of electronic states involved in all stages of the singlet fission reaction through their unique vibrational frequencies. This capability is demonstrated using a model singlet fission chromophore, 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-Pn). The alkyne groups of the TIPS side chains are coupled to the conjugated framework of the pentacene cores, enabling direct examination of the dynamics of triplet excitons that have successfully separated from correlated triplet pair states in crystalline films of TIPS-Pn. Relaxation processes during the separation of triplet excitons and triplet-triplet annihilation after their separation result in the formation of hot ground state molecules that also exhibit unique vibrational frequencies. Because all organic molecules possess native vibrational modes, ultrafast vibrational spectroscopy offers a new approach to examine the dynamics of electronic intermediates that may inform ongoing efforts to utilize singlet fission to overcome thermalization losses in photovoltaic applications.
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Affiliation(s)
- Christopher Grieco
- Department of Chemistry, The Pennsylvania State University , State College, Pennsylvania 16801, United States
| | - Eric R Kennehan
- Department of Chemistry, The Pennsylvania State University , State College, Pennsylvania 16801, United States
| | - Adam Rimshaw
- Department of Chemistry, The Pennsylvania State University , State College, Pennsylvania 16801, United States
| | - Marcia M Payne
- Department of Chemistry, University of Kentucky , Lexington, Kentucky 40506, United States
| | - John E Anthony
- Department of Chemistry, University of Kentucky , Lexington, Kentucky 40506, United States
| | - John B Asbury
- Department of Chemistry, The Pennsylvania State University , State College, Pennsylvania 16801, United States
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39
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Khan S, Mazumdar S. Theory of Transient Excited State Absorptions in Pentacene and Derivatives: Triplet-Triplet Biexciton versus Free Triplets. J Phys Chem Lett 2017; 8:5943-5948. [PMID: 29164900 DOI: 10.1021/acs.jpclett.7b02748] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Recent experiments in several singlet-fission materials have found that the triplet-triplet biexciton either is the primary product of photoexcitation or has a much longer lifetime than believed until now. It thus becomes essential to determine the difference in the spectroscopic signatures of the bound triplet-triplet and free triplets to distinguish between them optically. We report calculations of excited state absorptions (ESAs) from the singlet and triplet excitons and from the triplet-triplet biexciton for a pentacene crystal with the herringbone structure and for nanocrystals of bis(triisopropylsilylethynyl) (TIPS)-pentacene. The triplet-triplet biexciton absorbs in both the visible and the near-infrared (NIR), while the monomer free triplet absorbs only in the visible. The intensity of the NIR absorption depends on the extent of intermolecular coupling, in agreement with observations in TIPS-pentacene nanocrystals. We predict additional weak ESA from the triplet-triplet but not from the triplet, at still lower energy.
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Affiliation(s)
- Souratosh Khan
- Department of Physics, University of Arizona , Tucson, Arizona 85721, United States
| | - Sumit Mazumdar
- Department of Physics, University of Arizona , Tucson, Arizona 85721, United States
- Department of Chemistry and Biochemistry, University of Arizona , Tucson, Arizona 85721, United States
- College of Optical Sciences, University of Arizona , Tucson, Arizona 85721, United States
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40
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Khan S, Mazumdar S. Diagrammatic Exciton Basis Theory of the Photophysics of Pentacene Dimers. J Phys Chem Lett 2017; 8:4468-4478. [PMID: 28853895 DOI: 10.1021/acs.jpclett.7b01829] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Covalently linked acene dimers are of interest as candidates for intramolecular singlet fission. We report many-electron calculations of the energies and wave functions of the optical singlets, the lowest triplet exciton, and the triplet-triplet biexciton, as well as the final states of excited state absorptions from these states in a family of phenyl-linked pentacene dimers. While it is difficult to distinguish the triplet and the triplet-triplet from their transient absorptions in the 500-600 nm region, by comparing theoretical transient absorption spectra against earlier and very recent experimental transient absorptions in the near- and mid-infrared, we conclude that the end product of photoexcitation in these particular bipentacenes is the bound triplet-triplet and not free triplets. We predict additional transient absorptions at even longer wavelengths, beyond 1500 nm, to the equivalent of the classic 21Ag- in linear polyenes.
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Affiliation(s)
- Souratosh Khan
- Department of Physics, ‡Department of Chemistry and Biochemistry, and §College of Optical Sciences, University of Arizona , Tucson, Arizona 85721, United States
| | - Sumit Mazumdar
- Department of Physics, ‡Department of Chemistry and Biochemistry, and §College of Optical Sciences, University of Arizona , Tucson, Arizona 85721, United States
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41
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(Electro)chemical Oxidation of 6,13-Bis[tri(isopropyl)silylethynyl]pentacene to its Radical Cation and Dication. Chemphyschem 2017; 18:2266-2278. [DOI: 10.1002/cphc.201700435] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2017] [Revised: 06/04/2017] [Indexed: 11/07/2022]
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42
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Yong CK, Musser AJ, Bayliss SL, Lukman S, Tamura H, Bubnova O, Hallani RK, Meneau A, Resel R, Maruyama M, Hotta S, Herz LM, Beljonne D, Anthony JE, Clark J, Sirringhaus H. The entangled triplet pair state in acene and heteroacene materials. Nat Commun 2017; 8:15953. [PMID: 28699637 PMCID: PMC5510179 DOI: 10.1038/ncomms15953] [Citation(s) in RCA: 108] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Accepted: 05/17/2017] [Indexed: 12/18/2022] Open
Abstract
Entanglement of states is one of the most surprising and counter-intuitive consequences of quantum mechanics, with potent applications in cryptography and computing. In organic materials, one particularly significant manifestation is the spin-entangled triplet-pair state, which mediates the spin-conserving fission of one spin-0 singlet exciton into two spin-1 triplet excitons. Despite long theoretical and experimental exploration, the nature of the triplet-pair state and inter-triplet interactions have proved elusive. Here we use a range of organic semiconductors that undergo singlet exciton fission to reveal the photophysical properties of entangled triplet-pair states. We find that the triplet pair is bound with respect to free triplets with an energy that is largely material independent (∼30 meV). During its lifetime, the component triplets behave cooperatively as a singlet and emit light through a Herzberg-Teller-type mechanism, resulting in vibronically structured photoluminescence. In photovoltaic blends, charge transfer can occur from the bound triplet pairs with >100% photon-to-charge conversion efficiency.
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Affiliation(s)
- Chaw Keong Yong
- Cavendish Laboratory, Optoelectronics Group, University of Cambridge, Madingley Road, J.J. Thomson Avenue, Cambridge CB3 0HE, UK.,Department of Physics, University of California, Berkeley, California 94720, USA
| | - Andrew J Musser
- Cavendish Laboratory, Optoelectronics Group, University of Cambridge, Madingley Road, J.J. Thomson Avenue, Cambridge CB3 0HE, UK.,Department of Physics and Astronomy, The University of Sheffield, Hicks Buildling, Hounsfield Road, Sheffield S3 7RH, UK
| | - Sam L Bayliss
- Cavendish Laboratory, Optoelectronics Group, University of Cambridge, Madingley Road, J.J. Thomson Avenue, Cambridge CB3 0HE, UK
| | - Steven Lukman
- Cavendish Laboratory, Optoelectronics Group, University of Cambridge, Madingley Road, J.J. Thomson Avenue, Cambridge CB3 0HE, UK
| | - Hiroyuki Tamura
- Department of Chemical System Engineering, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Olga Bubnova
- Cavendish Laboratory, Optoelectronics Group, University of Cambridge, Madingley Road, J.J. Thomson Avenue, Cambridge CB3 0HE, UK
| | - Rawad K Hallani
- Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506-0055, USA
| | - Aurélie Meneau
- Cavendish Laboratory, Optoelectronics Group, University of Cambridge, Madingley Road, J.J. Thomson Avenue, Cambridge CB3 0HE, UK
| | - Roland Resel
- Institute of Solid State Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria
| | - Munetaka Maruyama
- Faculty of Materials Science and Engineering, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan
| | - Shu Hotta
- Faculty of Materials Science and Engineering, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan
| | - Laura M Herz
- Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, UK
| | - David Beljonne
- Laboratory for Chemistry of Novel Materials, University of Mons, Place du Parc 20, B-7000 Mons, Belgium
| | - John E Anthony
- Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506-0055, USA
| | - Jenny Clark
- Department of Physics and Astronomy, The University of Sheffield, Hicks Buildling, Hounsfield Road, Sheffield S3 7RH, UK
| | - Henning Sirringhaus
- Cavendish Laboratory, Optoelectronics Group, University of Cambridge, Madingley Road, J.J. Thomson Avenue, Cambridge CB3 0HE, UK
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43
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Sardar S. Monitoring of the energy levels by heteroatom substitution to hexacene and controlling over singlet fission and photo-oxidative resistance. J Mol Graph Model 2017; 74:24-37. [DOI: 10.1016/j.jmgm.2017.01.020] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Revised: 01/26/2017] [Accepted: 01/27/2017] [Indexed: 10/20/2022]
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44
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Synthesis, computational, and photophysical characterization of diaza-embedded [4]helicenes and pseudo[4]helicenes and their pyridinium and viologen homologues. Tetrahedron 2017. [DOI: 10.1016/j.tet.2016.12.032] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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45
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Ito S, Nagami T, Nakano M. Rational design of doubly-bridged chromophores for singlet fission and triplet–triplet annihilation. RSC Adv 2017. [DOI: 10.1039/c7ra06032g] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
A novel multiple-bridging realizes rational molecular design for efficient singlet fission and triplet–triplet annihilation.
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Affiliation(s)
- S. Ito
- Department of Materials Engineering Science
- Graduate School of Engineering Science
- Osaka University
- Toyonaka
- Japan
| | - T. Nagami
- Department of Materials Engineering Science
- Graduate School of Engineering Science
- Osaka University
- Toyonaka
- Japan
| | - M. Nakano
- Department of Materials Engineering Science
- Graduate School of Engineering Science
- Osaka University
- Toyonaka
- Japan
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46
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Pensack RD, Ostroumov EE, Tilley AJ, Mazza S, Grieco C, Thorley KJ, Asbury JB, Seferos DS, Anthony JE, Scholes GD. Observation of Two Triplet-Pair Intermediates in Singlet Exciton Fission. J Phys Chem Lett 2016; 7:2370-5. [PMID: 27281713 DOI: 10.1021/acs.jpclett.6b00947] [Citation(s) in RCA: 131] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Singlet fission is an excitation multiplication process in molecular systems that can circumvent energy losses and significantly boost solar cell efficiencies; however, the nature of a critical intermediate that enables singlet fission and details of its evolution into multiple product excitations remain obscure. We resolve the initial sequence of events comprising the fission of a singlet exciton in solids of pentacene derivatives using femtosecond transient absorption spectroscopy. We propose a three-step model of singlet fission that includes two triplet-pair intermediates and show how transient spectroscopy can distinguish initially interacting triplet pairs from those that are spatially separated and noninteracting. We find that the interconversion of these two triplet-pair intermediates is limited by the rate of triplet transfer. These results clearly highlight the classical kinetic model of singlet fission and expose subtle details that promise to aid in resolving problems associated with triplet extraction.
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Affiliation(s)
- Ryan D Pensack
- Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States
| | - Evgeny E Ostroumov
- Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States
| | - Andrew J Tilley
- Department of Chemistry, University of Toronto , Toronto, Ontario M5S 3H6, Canada
| | - Samuel Mazza
- Department of Chemistry, University of Kentucky , Lexington, Kentucky 40506, United States
| | - Christopher Grieco
- Department of Chemistry, The Pennsylvania State University , University Park, Pennsylvania 16802, United States
| | - Karl J Thorley
- Department of Chemistry, University of Kentucky , Lexington, Kentucky 40506, United States
| | - John B Asbury
- Department of Chemistry, The Pennsylvania State University , University Park, Pennsylvania 16802, United States
| | - Dwight S Seferos
- Department of Chemistry, University of Toronto , Toronto, Ontario M5S 3H6, Canada
| | - John E Anthony
- Department of Chemistry, University of Kentucky , Lexington, Kentucky 40506, United States
| | - Gregory D Scholes
- Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States
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47
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Hoff JJ, Zhu L, Dong Y, Albers T, Steel PJ, Cui X, Wen Y, Lebedyeva I, Miao S. Diazapentacene derivatives: synthesis, properties, and structures. RSC Adv 2016. [DOI: 10.1039/c6ra15359c] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Two soluble and stable diazapentacene derivatives were synthesized. DFT calculations and their chemical properties indicate that both compounds have potential application as ambipolar semiconductors.
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Affiliation(s)
- John J. Hoff
- Department of Chemistry and Physics
- Augusta University
- Augusta
- USA
| | - Lei Zhu
- College of Chemistry and Chemical Engineering
- Hunan University
- Changsha
- P. R. China
| | - Yutong Dong
- Department of Chemistry and Physics
- Augusta University
- Augusta
- USA
| | - Thomas Albers
- Department of Chemistry and Physics
- Augusta University
- Augusta
- USA
| | - Peter J. Steel
- Chemistry Department
- University of Canterbury
- Christchurch
- New Zealand
| | - Xianwei Cui
- College of Chemistry and Chemical Engineering
- Hunan University
- Changsha
- P. R. China
| | - Ying Wen
- College of Chemistry and Chemical Engineering
- Hunan University
- Changsha
- P. R. China
| | - Iryna Lebedyeva
- Department of Chemistry and Physics
- Augusta University
- Augusta
- USA
| | - Shaobin Miao
- Department of Chemistry and Physics
- Augusta University
- Augusta
- USA
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48
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Geyer FL, Brosius V, Bunz UHF. 2-Bromotetraazapentacene and Its Functionalization by Pd(0)-Chemistry. J Org Chem 2015; 80:12166-76. [DOI: 10.1021/acs.joc.5b02115] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Florian L. Geyer
- Organisch-Chemisches
Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer
Feld 270, 69120 Heidelberg, Germany
| | - Victor Brosius
- Organisch-Chemisches
Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer
Feld 270, 69120 Heidelberg, Germany
| | - Uwe H. F. Bunz
- Organisch-Chemisches
Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer
Feld 270, 69120 Heidelberg, Germany
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49
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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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