1
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Sperlich A, Eckstein KH, Oberndorfer F, Sturdza BK, Auth M, Dyakonov V, Mitric R, Hertel T. Onset of spin entanglement in doped carbon nanotubes studied by EPR. J Chem Phys 2024; 160:234702. [PMID: 38884403 DOI: 10.1063/5.0207502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2024] [Accepted: 05/14/2024] [Indexed: 06/18/2024] Open
Abstract
Nanoscale semiconductors with isolated spin impurities have been touted as promising materials for their potential use at the intersection of quantum, spin, and information technologies. Electron paramagnetic resonance (EPR) studies of spins in semiconducting carbon nanotubes have overwhelmingly focused on spins more strongly localized by sp3-type lattice defects. However, the creation of such impurities is irreversible and requires specific reactions to generate them. Shallow charge impurities, on the other hand, are more readily and widely produced by simple redox chemistry, but have not yet been investigated for their spin properties. Here, we use EPR to study p-doped (6,5) semiconducting single-wall carbon nanotubes (s-SWNTs) and elucidate the role of impurity-impurity interactions in conjunction with exchange and correlation effects for the spin behavior of this material. A quantitative comparison of the EPR signals with phenomenological modeling combined with configuration interaction electronic structure calculations of impurity pairs shows that orbital overlap, combined with exchange and correlation effects, causes the EPR signal to disappear due to spin entanglement for doping levels corresponding to impurity spacings of 14 nm (at 30 K). This transition is predicted to shift to higher doping levels with increasing temperature and to lower levels with increasing screening, providing an opportunity for improved spin control in doped s-SWNTs.
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Affiliation(s)
- Andreas Sperlich
- Experimental Physics 6 and Würzburg-Dresden Cluster of Excellence ct.qmat, Julius-Maximilians-Universität Würzburg, Würzburg, Germany
| | - Klaus H Eckstein
- Institute of Physical and Theoretical Chemistry, Julius-Maximilians-Universität Würzburg, Würzburg, Germany
| | - Florian Oberndorfer
- Institute of Physical and Theoretical Chemistry, Julius-Maximilians-Universität Würzburg, Würzburg, Germany
| | - Bernd K Sturdza
- Experimental Physics 6 and Würzburg-Dresden Cluster of Excellence ct.qmat, Julius-Maximilians-Universität Würzburg, Würzburg, Germany
| | - Michael Auth
- Experimental Physics 6 and Würzburg-Dresden Cluster of Excellence ct.qmat, Julius-Maximilians-Universität Würzburg, Würzburg, Germany
| | - Vladimir Dyakonov
- Experimental Physics 6 and Würzburg-Dresden Cluster of Excellence ct.qmat, Julius-Maximilians-Universität Würzburg, Würzburg, Germany
| | - Roland Mitric
- Institute of Physical and Theoretical Chemistry, Julius-Maximilians-Universität Würzburg, Würzburg, Germany
| | - Tobias Hertel
- Institute of Physical and Theoretical Chemistry, Julius-Maximilians-Universität Würzburg, Würzburg, Germany
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2
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Quill TJ, LeCroy G, Marks A, Hesse SA, Thiburce Q, McCulloch I, Tassone CJ, Takacs CJ, Giovannitti A, Salleo A. Charge Carrier Induced Structural Ordering And Disordering in Organic Mixed Ionic Electronic Conductors. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2310157. [PMID: 38198654 DOI: 10.1002/adma.202310157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2023] [Revised: 12/11/2023] [Indexed: 01/12/2024]
Abstract
Operational stability underpins the successful application of organic mixed ionic-electronic conductors (OMIECs) in a wide range of fields, including biosensing, neuromorphic computing, and wearable electronics. In this work, both the operation and stability of a p-type OMIEC material of various molecular weights are investigated. Electrochemical transistor measurements reveal that device operation is very stable for at least 300 charging/discharging cycles independent of molecular weight, provided the charge density is kept below the threshold where strong charge-charge interactions become likely. When electrochemically charged to higher charge densities, an increase in device hysteresis and a decrease in conductivity due to a drop in the hole mobility arising from long-range microstructural disruptions are observed. By employing operando X-ray scattering techniques, two regimes of polaron-induced structural changes are found: 1) polaron-induced structural ordering at low carrier densities, and 2) irreversible structural disordering that disrupts charge transport at high carrier densities, where charge-charge interactions are significant. These operando measurements also reveal that the transfer curve hysteresis at high carrier densities is accompanied by an analogous structural hysteresis, providing a microstructural basis for such instabilities. This work provides a mechanistic understanding of the structural dynamics and material instabilities of OMIEC materials during device operation.
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Affiliation(s)
- Tyler J Quill
- Department of Materials Science and Engineering, Stanford University, Stanford, CA, 94305, USA
| | - Garrett LeCroy
- Department of Materials Science and Engineering, Stanford University, Stanford, CA, 94305, USA
| | - Adam Marks
- Department of Materials Science and Engineering, Stanford University, Stanford, CA, 94305, USA
| | - Sarah A Hesse
- Stanford Synchrotron Radiation Lightsource SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA
| | - Quentin Thiburce
- Department of Materials Science and Engineering, Stanford University, Stanford, CA, 94305, USA
| | - Iain McCulloch
- Department of Chemistry University of Oxford, Oxford, OX1 3TA, UK
| | - Christopher J Tassone
- Stanford Synchrotron Radiation Lightsource SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA
| | - Christopher J Takacs
- Stanford Synchrotron Radiation Lightsource SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA
| | - Alexander Giovannitti
- Department of Materials Science and Engineering, Stanford University, Stanford, CA, 94305, USA
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Göteborg, SE-412 96, Sweden
| | - Alberto Salleo
- Department of Materials Science and Engineering, Stanford University, Stanford, CA, 94305, USA
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3
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Uratani H, Nakai H. Nanoscale and Real-Time Nuclear-Electronic Dynamics Simulation Study of Charge Transfer at the Donor-Acceptor Interface in Organic Photovoltaics. J Phys Chem Lett 2023; 14:2292-2300. [PMID: 36827224 DOI: 10.1021/acs.jpclett.2c03808] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Charge-transfer (CT) processes in donor-acceptor interfaces of organic photovoltaics have been challenging targets for computational chemistry owing to their nanoscale and ultrafast nature. Herein, we report real-time nuclear-electronic dynamics simulations of CT processes in a nanometer-scale donor-acceptor interface model composed of a donor poly(3-hexylthiophene-2,5-diyl) crystal and an acceptor [6,6]-phenyl-C61-butyric acid methyl ester aggregate. The simulations were realized using our original reduced-scaling computational technique, namely, patchwork-approximation-based Ehrenfest dynamics. The results illustrated the CT pathway with atomic resolution, thereby rationalizing the observed excitation-energy dependence of the quantity of CT. Further, nuclear motion, which is affected by the electronic dynamics, was observed to play a significant role in the CT process by modulating molecular orbital energies. The present study suggests that microscopic CT processes strongly depend on local structures of disordered donor-acceptor interfaces as well as coupling between nuclear and electronic dynamics.
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Affiliation(s)
- Hiroki Uratani
- Department of Chemistry and Biochemistry, School of Advanced Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan
| | - Hiromi Nakai
- Department of Chemistry and Biochemistry, School of Advanced Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan
- Waseda Research Institute for Science and Engineering (WISE), 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan
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4
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Nagatomo T, Vats AK, Matsuo K, Oyama S, Okamoto N, Suzuki M, Koganezawa T, Fuki M, Masuo S, Ohta K, Yamada H, Kobori Y. Nonpolymer Organic Solar Cells: Microscopic Phonon Control to Suppress Nonradiative Voltage Loss via Charge-Separated State. ACS PHYSICAL CHEMISTRY AU 2022; 3:207-221. [PMID: 36968446 PMCID: PMC10037453 DOI: 10.1021/acsphyschemau.2c00049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Revised: 12/19/2022] [Accepted: 12/20/2022] [Indexed: 12/31/2022]
Abstract
Recent remarkable developments on nonfullerene solar cells have reached a photoelectric conversion efficiency (PCE) of 18% by tuning the band energy levels in small molecular acceptors. In this regard, understanding the impact of small donor molecules on nonpolymer solar cells is essential. Here, we systematically investigated mechanisms of solar cell performance using diketopyrrolopyrrole (DPP)-tetrabenzoporphyrin (BP) conjugates of C4-DPP-H2BP and C4-DPP-ZnBP, where C4 represents the butyl group substituted at the DPP unit as small p-type molecules, while an acceptor of [6,6]-phenyl-C61-buthylic acid methyl ester is employed. We clarified the microscopic origins of the photocarrier caused by phonon-assisted one-dimensional (1D) electron-hole dissociations at the donor-acceptor interface. Using a time-resolved electron paramagnetic resonance, we have characterized controlled charge-recombination by manipulating disorders in π-π donor stacking. This ensures carrier transport through stacking molecular conformations to suppress nonradiative voltage loss capturing specific interfacial radical pairs separated by 1.8 nm in bulk-heterojunction solar cells. We show that, while disordered lattice motions by the π-π stackings via zinc ligation are essential to enhance the entropy for charge dissociations at the interface, too much ordered crystallinity causes the backscattering phonon to reduce the open-circuit voltage by geminate charge-recombination.
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Affiliation(s)
- Takaaki Nagatomo
- Department of Chemistry, Graduate School of Science, Kobe University, 1-1, Rokkodai-cho, Nada, Kobe657-8501, Japan
| | - Ajendra K. Vats
- Division of Materials Science, Graduate School of Science and Technology, Nara Institute of Science and Technology, 8916-5, Takayama-cho, Ikoma, Nara630-0192, Japan
| | - Kyohei Matsuo
- Division of Materials Science, Graduate School of Science and Technology, Nara Institute of Science and Technology, 8916-5, Takayama-cho, Ikoma, Nara630-0192, Japan
| | - Shinya Oyama
- Department of Chemistry, Graduate School of Science, Kobe University, 1-1, Rokkodai-cho, Nada, Kobe657-8501, Japan
| | - Naoya Okamoto
- Division of Materials Science, Graduate School of Science and Technology, Nara Institute of Science and Technology, 8916-5, Takayama-cho, Ikoma, Nara630-0192, Japan
| | - Mitsuharu Suzuki
- Division of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka565-0871, Japan
| | - Tomoyuki Koganezawa
- Japan Synchrotron Radiation Research Institute (JASRI), SPring-8, 1-1-1 Kouto, Sayo, Hyogo679-5198, Japan
| | - Masaaki Fuki
- Department of Chemistry, Graduate School of Science, Kobe University, 1-1, Rokkodai-cho, Nada, Kobe657-8501, Japan
- Molecular Photoscience Research Center, Kobe University, 1-1, Rokkodai-cho, Nada, Kobe657-8501, Japan
| | - Sadahiro Masuo
- Department of Applied Chemistry for Environment, Kwansei Gakuin University, 2-1, Gakuen, Sanda, Hyogo669-1337, Japan
| | - Kaoru Ohta
- Molecular Photoscience Research Center, Kobe University, 1-1, Rokkodai-cho, Nada, Kobe657-8501, Japan
| | - Hiroko Yamada
- Division of Materials Science, Graduate School of Science and Technology, Nara Institute of Science and Technology, 8916-5, Takayama-cho, Ikoma, Nara630-0192, Japan
| | - Yasuhiro Kobori
- Department of Chemistry, Graduate School of Science, Kobe University, 1-1, Rokkodai-cho, Nada, Kobe657-8501, Japan
- Molecular Photoscience Research Center, Kobe University, 1-1, Rokkodai-cho, Nada, Kobe657-8501, Japan
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5
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Krajewski M, Piotrowski P, Mech W, Korona KP, Wojtkiewicz J, Pilch M, Kaim A, Drabińska A, Kamińska M. Optical Properties and Light-Induced Charge Transfer in Selected Aromatic C60 Fullerene Derivatives and in Their Bulk Heterojunctions with Poly(3-Hexylthiophene). MATERIALS (BASEL, SWITZERLAND) 2022; 15:6908. [PMID: 36234249 PMCID: PMC9571621 DOI: 10.3390/ma15196908] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 09/26/2022] [Accepted: 09/28/2022] [Indexed: 06/16/2023]
Abstract
Fullerene derivatives offer great scope for modification of the basic molecule, often called a buckyball. In recent years, they have been the subject of numerous studies, in particular in terms of their applications, including in solar cells. Here, the properties of four recently synthesized fullerene C60 derivatives were examined regarding their optical properties and the efficiency of the charge transfer process, both in fullerene derivatives themselves and in their heterojunctions with poly (3-hexylthiophene). Optical absorption, electron spin resonance (ESR), and time-resolved photoluminescence (TRPL) techniques were applied to study the synthesized molecules. It was shown that the absorption processes in fullerene derivatives are dominated by absorption of the fullerene cage and do not significantly depend on the type of the derivative. It was also found by ESR and TRPL studies that asymmetrical, dipole-like derivatives exhibit stronger light-induced charge transfer properties than their symmetrical counterparts. The observed inhomogeneous broadening of the ESR lines indicated a large disorder of all polymer-fullerene derivative blends. The density functional theory was applied to explain the results of the optical absorption experiments.
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Affiliation(s)
- Maciej Krajewski
- Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
| | - Piotr Piotrowski
- Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland
| | - Wojciech Mech
- Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
| | | | - Jacek Wojtkiewicz
- Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
| | - Marek Pilch
- Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
| | - Andrzej Kaim
- Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland
| | - Aneta Drabińska
- Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
| | - Maria Kamińska
- Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
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6
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Dexter Tam TL, Moudgil A, Teh WJ, Wong ZM, Handoko AD, Chien SW, Yang SW, Yeo BS, Leong WL, Xu J. Polaron Delocalization Dependence of the Conductivity and the Seebeck Coefficient in Doped Conjugated Polymers. J Phys Chem B 2022; 126:2073-2085. [PMID: 35200014 DOI: 10.1021/acs.jpcb.2c00303] [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
Conjugated polymers are promising materials for thermoelectrics as they offer good performances at near ambient temperatures. The current focus on polymer thermoelectric research mainly targets a higher power factor (PF; a product of the conductivity and square of the Seebeck coefficient) through improving the charge mobility. This is usually accomplished via structural modification in conjugated polymers using different processing techniques and doping. As a result, the structure-charge transport relationship in conjugated polymers is generally well-established. In contrast, the relationship between the structure and the Seebeck coefficient is poorly understood due to its complex nature. A theoretical framework by David Emin (Phys. Rev. B, 1999, 59, 6205-6210) suggests that the Seebeck coefficient can be enhanced via carrier-induced vibrational softening, whose magnitude is governed by the size of the polaron. In this work, we seek to unravel this relationship in conjugated polymers using a series of highly identical pro-quinoid polymers. These polymers are ideal to test Emin's framework experimentally as the quinoid character and polaron delocalization in these polymers can be well controlled even by small atomic differences (<10 at. % per repeating unit). By increasing the polaron delocalization, that is, the polaron size, we demonstrate that both the conductivity and the Seebeck coefficient (and hence PF) can be increased simultaneously, and the latter is due to the increase in the polaron's vibrational entropy. By using literature data, we also show that this phenomenon can be observed in two closely related diketopyrrolopyrrole-conjugated polymers as well as in p-doped P3HT and PANI systems with an increasing molecular order.
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Affiliation(s)
- Teck Lip Dexter Tam
- Institute of Materials Research and Engineering (IMRE), Agency of Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis, Singapore 138634, Singapore
| | - Akshay Moudgil
- School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
| | - Wei Jie Teh
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
| | - Zicong Marvin Wong
- Institute of High Performance Computing (IHPC), Agency for Science, Technology and Research (A*STAR), 1 Fusionopolis Way, Connexis, Singapore 138632, Singapore
| | - Albertus Denny Handoko
- Institute of Materials Research and Engineering (IMRE), Agency of Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis, Singapore 138634, Singapore
| | - Sheau Wei Chien
- Institute of Materials Research and Engineering (IMRE), Agency of Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis, Singapore 138634, Singapore
| | - Shuo-Wang Yang
- Institute of High Performance Computing (IHPC), Agency for Science, Technology and Research (A*STAR), 1 Fusionopolis Way, Connexis, Singapore 138632, Singapore
| | - Boon Siang Yeo
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
| | - Wei Lin Leong
- School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.,School of Chemical and Biomedical Engineering, Nanyang Technological University, 50 Nanyang Drive, Singapore 637459, Singapore
| | - Jianwei Xu
- Institute of Materials Research and Engineering (IMRE), Agency of Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis, Singapore 138634, Singapore.,Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
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7
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Liu Q, Huang W, Liu B, Wang PC, Chen HB. Experimental and Theoretical Study of Gamma Radiolysis and Dose Rate Effect of o-Cresol Formaldehyde Epoxy Composites. ACS APPLIED MATERIALS & INTERFACES 2022; 14:5959-5972. [PMID: 35049269 DOI: 10.1021/acsami.1c19609] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Gamma radiolysis behaviors and mechanisms of silica-filled o-cresol formaldehyde epoxy are studied at 2.20 × 10-5 to 1.95 × 10-1 Gy/s. The radiolysis-induced changes in chemical structures do not severely affect its thermostability. The slightly deteriorated mechanical strength at temperature exceeding 100 °C is accompanied by the declining glass transition temperature (from 185.9 to 172.2 °C) and enhanced damping ability. The gas yields of hydrogen, methane, and carbon dioxide manifest a remarkable dose rate effect. Based on the Schwarzschild law, their yields at an extremely low dose rate are accurately predicted by the established master curves. Besides, the latent radiolysis of gas products and postradiation effect are found with caution. The radiation-caused residual spin species are proved to be composed of silica defects and a phenoxy-type free radical with a tert-butyl group, according to the experimental results, theoretical calculations, and spectra simulations. The lower vertical ionization potential (7.6 eV) and adiabatic ionization potential (7.1 eV) are primarily due to the ionization of the benzene ring moiety with the tert-butyl group, which is likely to suffer from radiolysis. The calculated bond dissociation energy (260.8-563.5 kJ/mol) of the typical chemical bonds of epoxy is consistent with its radiolytic vulnerability and degradation mechanisms.
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Affiliation(s)
- Qiang Liu
- Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621000, China
| | - Wei Huang
- Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621000, China
| | - Bo Liu
- Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621000, China
| | - Pu-Cheng Wang
- Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621000, China
| | - Hong-Bing Chen
- Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621000, China
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8
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Rastegaralam M, Rastegaralam M. Significant enhancement of thermoelectric properties of conducting
PTB7
polymer by addition of appropriate dopants. J Appl Polym Sci 2021. [DOI: 10.1002/app.51378] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Mina Rastegaralam
- Department of Electrical and Computer Engineering Inter‐University Semiconductor Research Center, Seoul National University Seoul South Korea
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9
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Weissenseel S, Gottscholl A, Bönnighausen R, Dyakonov V, Sperlich A. Long-lived spin-polarized intermolecular exciplex states in thermally activated delayed fluorescence-based organic light-emitting diodes. SCIENCE ADVANCES 2021; 7:eabj9961. [PMID: 34788086 PMCID: PMC8598001 DOI: 10.1126/sciadv.abj9961] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Accepted: 09/28/2021] [Indexed: 06/13/2023]
Abstract
Spin-spin interactions in organic light-emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF) are pivotal because radiative recombination is largely determined by triplet-to-singlet conversion, also called reverse intersystem crossing (RISC). To explore the underlying process, we apply a spin-resonance spectral hole-burning technique to probe electroluminescence. We find that the triplet exciplex states in OLEDs are highly spin-polarized and show that these states can be decoupled from the heterogeneous nuclear environment as a source of spin dephasing and can even be coherently manipulated on a spin-spin relaxation time scale T2* of 30 ns. Crucially, we obtain the characteristic triplet exciplex spin-lattice relaxation time T1 in the range of 50 μs, which far exceeds the RISC time. We conclude that slow spin relaxation rather than RISC is an efficiency-limiting step for intermolecular donor:acceptor systems. Finding TADF emitters with faster spin relaxation will benefit this type of TADF OLEDs.
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10
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The role of charge recombination to triplet excitons in organic solar cells. Nature 2021; 597:666-671. [PMID: 34588666 DOI: 10.1038/s41586-021-03840-5] [Citation(s) in RCA: 114] [Impact Index Per Article: 38.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Accepted: 07/20/2021] [Indexed: 11/08/2022]
Abstract
The use of non-fullerene acceptors (NFAs) in organic solar cells has led to power conversion efficiencies as high as 18%1. However, organic solar cells are still less efficient than inorganic solar cells, which typically have power conversion efficiencies of more than 20%2. A key reason for this difference is that organic solar cells have low open-circuit voltages relative to their optical bandgaps3, owing to non-radiative recombination4. For organic solar cells to compete with inorganic solar cells in terms of efficiency, non-radiative loss pathways must be identified and suppressed. Here we show that in most organic solar cells that use NFAs, the majority of charge recombination under open-circuit conditions proceeds via the formation of non-emissive NFA triplet excitons; in the benchmark PM6:Y6 blend5, this fraction reaches 90%, reducing the open-circuit voltage by 60 mV. We prevent recombination via this non-radiative channel by engineering substantial hybridization between the NFA triplet excitons and the spin-triplet charge-transfer excitons. Modelling suggests that the rate of back charge transfer from spin-triplet charge-transfer excitons to molecular triplet excitons may be reduced by an order of magnitude, enabling re-dissociation of the spin-triplet charge-transfer exciton. We demonstrate NFA systems in which the formation of triplet excitons is suppressed. This work thus provides a design pathway for organic solar cells with power conversion efficiencies of 20% or more.
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11
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Park S, Schultz T, Shin D, Mutz N, Aljarb A, Kang HS, Lee CH, Li LJ, Xu X, Tung V, List-Kratochvil EJW, Blumstengel S, Amsalem P, Koch N. The Schottky-Mott Rule Expanded for Two-Dimensional Semiconductors: Influence of Substrate Dielectric Screening. ACS NANO 2021; 15:14794-14803. [PMID: 34379410 DOI: 10.1021/acsnano.1c04825] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
A comprehensive understanding of the energy level alignment mechanisms between two-dimensional (2D) semiconductors and electrodes is currently lacking, but it is a prerequisite for tailoring the interface electronic properties to the requirements of device applications. Here, we use angle-resolved direct and inverse photoelectron spectroscopy to unravel the key factors that determine the level alignment at interfaces between a monolayer of the prototypical 2D semiconductor MoS2 and conductor, semiconductor, and insulator substrates. For substrate work function (Φsub) values below 4.5 eV we find that Fermi level pinning occurs, involving electron transfer to native MoS2 gap states below the conduction band. For Φsub above 4.5 eV, vacuum level alignment prevails but the charge injection barriers do not strictly follow the changes of Φsub as expected from the Schottky-Mott rule. Notably, even the trends of the injection barriers for holes and electrons are different. This is caused by the band gap renormalization of monolayer MoS2 by dielectric screening, which depends on the dielectric constant (εr) of the substrate. Based on these observations, we introduce an expanded Schottky-Mott rule that accounts for band gap renormalization by εr -dependent screening and show that it can accurately predict charge injection barriers for monolayer MoS2. It is proposed that the formalism of the expanded Schottky-Mott rule should be universally applicable for 2D semiconductors, provided that material-specific experimental benchmark data are available.
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Affiliation(s)
- Soohyung Park
- Advanced Analysis Center, Korea Institute of Science and Technology (KIST), Seoul 02792, South Korea
| | - Thorsten Schultz
- Humboldt-Universität zu Berlin, Institut für Physik & IRIS Adlershof, Brook-Taylor Straße 6, 12489 Berlin, Germany
- Helmholtz-Zentrum für Materialien und Energie GmbH, Bereich Solarenergieforschung, Albert-Einstein Straße 15, 12489 Berlin, Germany
| | - Dongguen Shin
- Humboldt-Universität zu Berlin, Institut für Physik & IRIS Adlershof, Brook-Taylor Straße 6, 12489 Berlin, Germany
| | - Niklas Mutz
- Humboldt-Universität zu Berlin, Institut für Physik & IRIS Adlershof, Brook-Taylor Straße 6, 12489 Berlin, Germany
- Humboldt-Universität zu Berlin, Institut für Chemie, Brook-Taylor Straße 6, 12489 Berlin, Germany
| | - Areej Aljarb
- Physical Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
- Department of Physics, King Abdulaziz University, Jeddah 21589, Kingdom of Saudi Arabia
| | - Hee Seong Kang
- KU-KIST Graduate School of Converging Science and Technology & Department of Integrative Energy Engineering, Korea University, Seoul 02841, Republic of Korea
- Advanced Materials Research Division, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea
| | - Chul-Ho Lee
- KU-KIST Graduate School of Converging Science and Technology & Department of Integrative Energy Engineering, Korea University, Seoul 02841, Republic of Korea
- Advanced Materials Research Division, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea
| | - Lain-Jong Li
- Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong
| | - Xiaomin Xu
- Tsinghua-Berkeley Shenzhen Institute & Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, China
| | - Vincent Tung
- Physical Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
| | - Emil J W List-Kratochvil
- Humboldt-Universität zu Berlin, Institut für Physik & IRIS Adlershof, Brook-Taylor Straße 6, 12489 Berlin, Germany
- Helmholtz-Zentrum für Materialien und Energie GmbH, Bereich Solarenergieforschung, Albert-Einstein Straße 15, 12489 Berlin, Germany
- Humboldt-Universität zu Berlin, Institut für Chemie, Brook-Taylor Straße 6, 12489 Berlin, Germany
| | - Sylke Blumstengel
- Humboldt-Universität zu Berlin, Institut für Physik & IRIS Adlershof, Brook-Taylor Straße 6, 12489 Berlin, Germany
- Humboldt-Universität zu Berlin, Institut für Chemie, Brook-Taylor Straße 6, 12489 Berlin, Germany
| | - Patrick Amsalem
- Humboldt-Universität zu Berlin, Institut für Physik & IRIS Adlershof, Brook-Taylor Straße 6, 12489 Berlin, Germany
| | - Norbert Koch
- Humboldt-Universität zu Berlin, Institut für Physik & IRIS Adlershof, Brook-Taylor Straße 6, 12489 Berlin, Germany
- Helmholtz-Zentrum für Materialien und Energie GmbH, Bereich Solarenergieforschung, Albert-Einstein Straße 15, 12489 Berlin, Germany
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12
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Rastegaralam M, Rastegaralam M. Significant Enhancement of Thermoelectric Properties of PTB7 Conducting Polymer by Mixed-Solvent Approach. J Phys Chem B 2021; 125:9910-9915. [PMID: 34425049 DOI: 10.1021/acs.jpcb.1c06222] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The thermoelectric properties of poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}), commonly known as PTB7 conducting polymer, were investigated for the first time by Rastegaralam et al. in 2017 [ Crystals 2017, 7, 292]. PTB7 showed higher electrical conductivity or Seebeck coefficient (or even both) and, hence, a higher thermoelectric power factor than a variety of organic semiconductors. Therefore, it is worth working more on this semiconductor to improve its thermoelectric figure of merit. In this work, for the first time the effect of cosolvents on the thermoelectric properties of PTB7 is investigated. PTB7 conducting polymer dissolved in chlorobenzene was treated with different solvents: N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), acetonitrile (AC), and 1,2-dichloroethane (DCE). Upon addition of DMF, DMSO, and NMP, a significant enhancement in the electrical conductivity of the samples accompanied by a reduction in the Seebeck coefficient occurred as a result of doping, while the use of AC and DCE led to simultaneous enhancement in the electrical conductivity and the Seebeck coefficient by increasing the mobility. The dopants used in this work are inexpensive, are easily available, and do not need to perform any synthesis process. The highest estimated figure of merit value obtained in this work without optimization is 0.1, which is of the highest values for organic thermoelectric materials.
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Affiliation(s)
- Mina Rastegaralam
- Department of Electrical and Computer Engineering, Inter-University Semiconductor Research Center, Seoul National University, Seoul 08826, South Korea
| | - Mitra Rastegaralam
- Lar Consulting Engineers Company, No. 30, Sharifi Avenue, Vanak Square, 1969944311,Tehran, Iran
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13
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Krinichnyi VI, Yudanova EI. Magnetic-field-controlled charge transport in organic polymer composites. Chem Phys Lett 2021. [DOI: 10.1016/j.cplett.2021.138787] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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14
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Yudanova EI, Krinichnyi VI, Denisov NN. EPR Study of Photogeneration of Spin Charge Carriers in Fullerene-Free Polymer Composites PBDB-T : IT-M. HIGH ENERGY CHEMISTRY 2021. [DOI: 10.1134/s0018143921040160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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15
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Kobeleva E, Popov A, Baranov D, Uvarov M, Nevostruev D, Degtyarenko K, Gadirov R, Sukhikh A, Kulik L. Origin of poor photovoltaic performance of bis(tetracyanoantrathiophene) non-fullerene acceptor. Chem Phys 2021. [DOI: 10.1016/j.chemphys.2021.111162] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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16
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Tait CE, Reckwitz A, Arvind M, Neher D, Bittl R, Behrends J. Spin-spin interactions and spin delocalisation in a doped organic semiconductor probed by EPR spectroscopy. Phys Chem Chem Phys 2021; 23:13827-13841. [PMID: 34151324 DOI: 10.1039/d1cp02133h] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The enhancement and control of the electrical conductivity of organic semiconductors is fundamental for their use in optoelectronic applications and can be achieved by molecular doping, which introduces additional charge carriers through electron transfer between a dopant molecule and the organic semiconductor. Here, we use Electron Paramagnetic Resonance (EPR) spectroscopy to characterise the unpaired spins associated with the charges generated by molecular doping of the prototypical organic semiconductor poly(3-hexylthiophene) (P3HT) with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) and tris(pentafluorophenyl)borane (BCF). The EPR results reveal the P3HT radical cation as the only paramagnetic species in BCF-doped P3HT films and show evidence for increased mobility of the detected spins at high doping concentrations as well as formation of antiferromagnetically coupled spin pairs leading to decreased spin concentrations at low temperatures. The EPR signature for F4TCNQ-doped P3HT is found to be determined by spin exchange between P3HT radical cations and F4TCNQ radical anions. Results from continuous-wave and pulse EPR measurements suggest the presence of the unpaired spin on P3HT in a multitude of environments, ranging from free P3HT radical cations with similar properties to those observed in BCF-doped P3HT, to pairs of dipolar and exchange-coupled spins on P3HT and the dopant anion. Characterisation of the proton hyperfine interactions by ENDOR allowed quantification of the extent of spin delocalisation and revealed reduced delocalisation in the F4TCNQ-doped P3HT films.
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Affiliation(s)
- Claudia E Tait
- Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany. and Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, OX1 3QZ Oxford, UK
| | - Anna Reckwitz
- Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
| | - Malavika Arvind
- Institute of Physics and Astronomy, Universität Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany
| | - Dieter Neher
- Institute of Physics and Astronomy, Universität Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany
| | - Robert Bittl
- Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
| | - Jan Behrends
- Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
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17
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Yudanova EI, Krinichnyi VI, Denisov NN. Light-Induced EPR Study of the Effect of Coumarin Trace Additives on Spin Dynamics in the P3DDT/PC61BM Polymer Composite. HIGH ENERGY CHEMISTRY 2020. [DOI: 10.1134/s0018143920040128] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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18
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Arvind M, Tait CE, Guerrini M, Krumland J, Valencia AM, Cocchi C, Mansour AE, Koch N, Barlow S, Marder SR, Behrends J, Neher D. Quantitative Analysis of Doping-Induced Polarons and Charge-Transfer Complexes of Poly(3-hexylthiophene) in Solution. J Phys Chem B 2020; 124:7694-7708. [DOI: 10.1021/acs.jpcb.0c03517] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Malavika Arvind
- Institut für Physik und Astronomie, Universität Potsdam, 14476 Potsdam, Germany
| | - Claudia E. Tait
- Institut für Experimentalphysik, Berlin Joint EPR Lab, Freie Universität Berlin, 14195 Berlin, Germany
| | - Michele Guerrini
- Institut für Physik and IRIS Adlershof, Humboldt-Universität zu Berlin, 12489 Berlin, Germany
- Institut für Physik, Carl von Ossietzky Universität Oldenburg, 26129 Oldenburg, Germany
| | - Jannis Krumland
- Institut für Physik and IRIS Adlershof, Humboldt-Universität zu Berlin, 12489 Berlin, Germany
| | - Ana M. Valencia
- Institut für Physik and IRIS Adlershof, Humboldt-Universität zu Berlin, 12489 Berlin, Germany
- Institut für Physik, Carl von Ossietzky Universität Oldenburg, 26129 Oldenburg, Germany
| | - Caterina Cocchi
- Institut für Physik and IRIS Adlershof, Humboldt-Universität zu Berlin, 12489 Berlin, Germany
- Institut für Physik, Carl von Ossietzky Universität Oldenburg, 26129 Oldenburg, Germany
| | - Ahmed E. Mansour
- Institut für Physik and IRIS Adlershof, Humboldt-Universität zu Berlin, 12489 Berlin, Germany
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, 12489 Berlin, Germany
| | - Norbert Koch
- Institut für Physik and IRIS Adlershof, Humboldt-Universität zu Berlin, 12489 Berlin, Germany
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, 12489 Berlin, Germany
| | - Stephen Barlow
- School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, United States
| | - Seth R. Marder
- School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, United States
| | - Jan Behrends
- Institut für Experimentalphysik, Berlin Joint EPR Lab, Freie Universität Berlin, 14195 Berlin, Germany
| | - Dieter Neher
- Institut für Physik und Astronomie, Universität Potsdam, 14476 Potsdam, Germany
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19
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Yaghoobi F, Salehzadeh S, Maddah M. Quantum mechanics and molecular dynamics studies on the C…H interaction between small fullerenes (C36 and C24) and [M(H2O)6]2+ (M = Ca2+, Zn2+) cations. J Mol Liq 2020. [DOI: 10.1016/j.molliq.2019.112339] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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20
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Beletskaya EA, Lukina EA, Uvarov MN, Popov AA, Kulik LV. Geminate recombination in organic photovoltaic blend PCDTBT/PC 71BM studied by out-of-phase electron spin echo spectroscopy. J Chem Phys 2020; 152:044706. [PMID: 32007084 DOI: 10.1063/1.5131855] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The key process in organic solar cell operation is charge separation under light illumination. Due to the low dielectric constant of organic materials, the Coulomb attraction energy within the interfacial charge-transfer state (CTS) is larger than the thermal energy. Understanding the mechanism of charge separation at the organic donor/acceptor interface still remains a challenge and requires knowledge of the CTS temporal evolution. To address this problem, the CTS in the benchmark photovoltaic blend PCDTBT/PC71BM was studied by the out-of-phase Electron Spin Echo (ESE). The protocol for determining the CTS geminate recombination rate for certain electron-hole distances was developed. Simulating the out-of-phase ESE trace for the CTS in the PCDTBT/PC71BM blend allows precise determination of the electron-hole distance distribution function and its evolution with the increase in the delay after the laser flash. Distances of charge separation up to 6 nm were detected upon thermalization at a temperature of 20 K. Assuming the exponential decay of the recombination rate, the attenuation factor β = 0.08 Å-1 is estimated for the PCDTBT/PC71BM blend. Such a low attenuation factor is probably caused by a high degree of hole delocalization along the PCDTBT chain.
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Affiliation(s)
- E A Beletskaya
- Voevodsky Institute of Chemical Kinetics and Combustion SB RAS, Institutskaya Str. 3, 630090 Novosibirsk, Russia
| | - E A Lukina
- Voevodsky Institute of Chemical Kinetics and Combustion SB RAS, Institutskaya Str. 3, 630090 Novosibirsk, Russia
| | - M N Uvarov
- Voevodsky Institute of Chemical Kinetics and Combustion SB RAS, Institutskaya Str. 3, 630090 Novosibirsk, Russia
| | - A A Popov
- Voevodsky Institute of Chemical Kinetics and Combustion SB RAS, Institutskaya Str. 3, 630090 Novosibirsk, Russia
| | - L V Kulik
- Voevodsky Institute of Chemical Kinetics and Combustion SB RAS, Institutskaya Str. 3, 630090 Novosibirsk, Russia
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21
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Irgen-Gioro S, Roy P, Padgaonkar S, Harel E. Low energy excited state vibrations revealed in conjugated copolymer PCDTBT. J Chem Phys 2020; 152:044201. [DOI: 10.1063/1.5132299] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Affiliation(s)
- Shawn Irgen-Gioro
- Department of Chemistry, Northwestern University, 2145 Sheridan Rd. Evanston, Illinois 60208, USA
| | - Palas Roy
- Department of Chemistry, Northwestern University, 2145 Sheridan Rd. Evanston, Illinois 60208, USA
- School of Chemistry, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, United Kingdom
| | - Suyog Padgaonkar
- Department of Chemistry, Northwestern University, 2145 Sheridan Rd. Evanston, Illinois 60208, USA
| | - Elad Harel
- Department of Chemistry, Northwestern University, 2145 Sheridan Rd. Evanston, Illinois 60208, USA
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, USA
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22
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Niklas J, Zheng T, Neshchadin A, Mardis KL, Yu L, Poluektov OG. Polaron and Exciton Delocalization in Oligomers of High-Performance Polymer PTB7. J Am Chem Soc 2020; 142:1359-1366. [PMID: 31860294 DOI: 10.1021/jacs.9b10859] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A key characteristic of organic photovoltaic cells is the efficient charge separation in the active layer. Sufficient delocalization of the positive polaron in organic photovoltaics is considered essential for the effective separation of the opposite charges and the suppression of recombination. We use light-induced EPR and ENDOR spectroscopy combined with DFT calculations to determine the electronic structure of the positive polaron in PTB7-type oligomers. Utilizing the superior spectral resolution of high-frequency (130 GHz) D-band EPR, the principal components of the g tensors were determined. Pulsed ENDOR spectroscopy at X-band allowed the measurement of 1H hyperfine coupling constants. A comparison of g tensors and 1H hyperfine coupling constants of the PTB7-type oligomers with the high-performance PTB7 polymer revealed a delocalization of the positive polaron in the polymer over about four monomeric units, corresponding to about 45 Å in length. Our current study thus not only determines the polaron delocalization length in PTB7 but also validates the approach combining EPR/ENDOR spectroscopy with DFT-calculated magnetic resonance parameters. This is of importance in those cases where oligomers of defined length are not easily obtained. In addition, the delocalization of the neutral triplet exciton was also determined in the oligomers and compared with polymer PTB7. The analysis revealed that the neutral triplet exciton is substantially more delocalized than the positive polaron, exceeding 10 monomeric units.
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Affiliation(s)
- Jens Niklas
- Chemical Sciences and Engineering Division , Argonne National Laboratory , Lemont , Illinois 60439 , United States
| | - Tianyue Zheng
- Department of Chemistry and James Franck Institute , University of Chicago , Chicago , Illinois 60637 , United States
| | - Andriy Neshchadin
- Department of Chemistry and James Franck Institute , University of Chicago , Chicago , Illinois 60637 , United States
| | - Kristy L Mardis
- Department of Chemistry, Physics, and Engineering Studies , Chicago State University , Chicago , Illinois 60628 , United States
| | - Luping Yu
- Department of Chemistry and James Franck Institute , University of Chicago , Chicago , Illinois 60637 , United States
| | - Oleg G Poluektov
- Chemical Sciences and Engineering Division , Argonne National Laboratory , Lemont , Illinois 60439 , United States
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23
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Yurash B, Cao DX, Brus VV, Leifert D, Wang M, Dixon A, Seifrid M, Mansour AE, Lungwitz D, Liu T, Santiago PJ, Graham KR, Koch N, Bazan GC, Nguyen TQ. Towards understanding the doping mechanism of organic semiconductors by Lewis acids. NATURE MATERIALS 2019; 18:1327-1334. [PMID: 31527809 DOI: 10.1038/s41563-019-0479-0] [Citation(s) in RCA: 61] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2019] [Accepted: 08/10/2019] [Indexed: 06/10/2023]
Abstract
Precise doping of organic semiconductors allows control over the conductivity of these materials, an essential parameter in electronic applications. Although Lewis acids have recently shown promise as dopants for solution-processed polymers, their doping mechanism is not yet fully understood. In this study, we found that B(C6F5)3 is a superior dopant to the other Lewis acids investigated (BF3, BBr3 and AlCl3). Experiments indicate that Lewis acid-base adduct formation with polymers inhibits the doping process. Electron-nuclear double-resonance and nuclear magnetic resonance experiments, together with density functional theory, show that p-type doping occurs by generation of a water-Lewis acid complex with substantial Brønsted acidity, followed by protonation of the polymer backbone and electron transfer from a neutral chain segment to a positively charged, protonated one. This study provides insight into a potential path for protonic acid doping and shows how trace levels of water can transform Lewis acids into powerful Brønsted acids.
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Affiliation(s)
- Brett Yurash
- Center for Polymers and Organic Solids, Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA
| | - David Xi Cao
- Center for Polymers and Organic Solids, Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA
| | - Viktor V Brus
- Center for Polymers and Organic Solids, Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA
| | - Dirk Leifert
- Center for Polymers and Organic Solids, Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA
| | - Ming Wang
- Center for Advanced Low-Dimension Materials, Donghua University, Shanghai, China
| | - Alana Dixon
- Center for Polymers and Organic Solids, Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA
| | - Martin Seifrid
- Center for Polymers and Organic Solids, Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA
| | - Ahmed E Mansour
- Institut für Physik & IRIS Adlershof, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Dominique Lungwitz
- Institut für Physik & IRIS Adlershof, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Tuo Liu
- Department of Chemistry, University of Kentucky, Lexington, KY, USA
| | - Peter J Santiago
- Center for Polymers and Organic Solids, Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA
| | - Kenneth R Graham
- Department of Chemistry, University of Kentucky, Lexington, KY, USA
| | - Norbert Koch
- Institut für Physik & IRIS Adlershof, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Guillermo C Bazan
- Center for Polymers and Organic Solids, Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA.
| | - Thuc-Quyen Nguyen
- Center for Polymers and Organic Solids, Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA.
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24
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Van Landeghem M, Lenaerts R, Kesters J, Maes W, Goovaerts E. Impact of the donor polymer on recombination via triplet excitons in a fullerene-free organic solar cell. Phys Chem Chem Phys 2019; 21:22999-23008. [PMID: 31599899 DOI: 10.1039/c9cp03793d] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The greater chemical tunability of non-fullerene acceptors enables fine-tuning of the donor-acceptor energy level offsets, a promising strategy towards increasing the open-circuit voltage in organic solar cells. Unfortunately, this approach could open an additional recombination channel for the charge-transfer (CT) state via a lower-lying donor or acceptor triplet level. In this work we investigate such electron and hole back-transfer mechanisms in fullerene-free solar cells incorporating the novel molecular acceptor 2,4-diCN-Ph-DTTzTz. The transition to the low-driving force regime is studied by comparing blends with well-established donor polymers P3HT and MDMO-PPV, which allows for variation of the energetic offsets at the donor-acceptor interface. Combining various optical spectroscopic techniques, the CT process and subsequent triplet formation are systematically investigated. Although both back-transfer mechanisms are found to be energetically feasible in both blends, markedly different triplet-mediated recombination processes are observed for the two systems. The kinetic suppression of electron back-transfer in the blend with P3HT suggests that energy losses due to triplet formation on the polymer can be avoided, regardless of favorable energetic alignment.
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Affiliation(s)
- Melissa Van Landeghem
- Physics Department, University of Antwerp, Universiteitsplein 1, 2610 Antwerp, Belgium.
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25
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Rachmat VAA, Kubodera T, Son D, Cho Y, Marumoto K. Molecular Oriented Charge Accumulation in High-Efficiency Polymer Solar Cells as Revealed by Operando Spin Analysis. ACS APPLIED MATERIALS & INTERFACES 2019; 11:31129-31138. [PMID: 31370398 DOI: 10.1021/acsami.9b10309] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
A low band-gap polymer, PTB7-Th, is one of the typical p-type semiconductors among the next-generation solar-cell materials that have achieved power conversion efficiencies of over 10%. However, the internal deterioration mechanism of high-efficiency polymer solar cells such as PTB7-Th-based cells is still an open issue and has been extensively studied. Here, we report a study with operando electron spin resonance (ESR) spectroscopy for PTB7-Th polymer solar cells with an n-type semiconductor PC71BM to clarify the internal deterioration mechanism at a molecular level. We have directly observed ambipolar charge accumulation with a face-on molecular orientation in the cells under simulated solar irradiation using an operando light-induced ESR technique. Moreover, we have found a clear correlation between the charge accumulation and performance deterioration of the cells. The charge accumulation sites have been clarified by the ESR analysis and density functional theory calculation. The prevention of such charge accumulation on the basis of the present finding would be important for the commercialization of high-efficiency polymer solar cells.
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Affiliation(s)
| | - Takaya Kubodera
- Division of Materials Science , University of Tsukuba , Tsukuba , Ibaraki 305-8573 , Japan
| | - Donghyun Son
- Division of Materials Science , University of Tsukuba , Tsukuba , Ibaraki 305-8573 , Japan
| | - Yujin Cho
- Semiconductor Device Materials Group, Nano Materials Field, International Center for Materials Nanoarchitectonics (MANA) , National Institute for Materials Science (NIMS) , 1-1 Namiki , Tsukuba , Ibaraki 305-0044 , Japan
| | - Kazuhiro Marumoto
- Division of Materials Science , University of Tsukuba , Tsukuba , Ibaraki 305-8573 , Japan
- Tsukuba Research Center for Energy Materials Science (TREMS) , University of Tsukuba , Tsukuba , Ibaraki 305-8571 , Japan
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26
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Yudanova EI, Krinichnyi VI, Bogatyrenko VR, Denisov NN, Nazarov DI. Influence of Photogeneration Frequency on the Transport of Spin Charge Carriers in the Copolymer–Methanofullerene Composite: EPR Study. HIGH ENERGY CHEMISTRY 2019. [DOI: 10.1134/s0018143919030159] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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27
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Krinichnyi VI, Yudanova EI, Bogatyrenko VR. Light-induced EPR study of spin-assisted charge transport in PFOT:PC61BM composite. J Photochem Photobiol A Chem 2019. [DOI: 10.1016/j.jphotochem.2018.12.032] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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28
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Moral M, Domínguez R, Fernández-Liencres MP, Garzón-Ruiz A, García-Martínez JC, Navarro A. Photophysical features and semiconducting properties of propeller-shaped oligo(styryl)benzenes. J Chem Phys 2019; 150:064309. [DOI: 10.1063/1.5079935] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Affiliation(s)
- Mónica Moral
- Renewable Energy Research Institute, University of Castilla-La Mancha, Paseo de la Investigación 1, 02071 Albacete, Spain
| | - Rocío Domínguez
- Department of Inorganic, Organic Chemistry and Biochemistry, Faculty of Pharmacy, University of Castilla-La Mancha, 02071 Albacete, Spain
- Regional Center for Biomedical Research (CRIB), C/ Almansa s/n, 02071 Albacete, Spain
| | - M. Paz Fernández-Liencres
- Department of Physical and Analytical Chemistry, Faculty of Experimental Sciences, Universidad de Jaén, 23071 Jaén, Spain
| | - Andrés Garzón-Ruiz
- Department of Physical Chemistry, Faculty of Pharmacy, University of Castilla-La Mancha, 02071 Albacete, Spain
| | - Joaquín C. García-Martínez
- Department of Inorganic, Organic Chemistry and Biochemistry, Faculty of Pharmacy, University of Castilla-La Mancha, 02071 Albacete, Spain
- Regional Center for Biomedical Research (CRIB), C/ Almansa s/n, 02071 Albacete, Spain
| | - Amparo Navarro
- Department of Physical and Analytical Chemistry, Faculty of Experimental Sciences, Universidad de Jaén, 23071 Jaén, Spain
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29
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Biskup T. Structure-Function Relationship of Organic Semiconductors: Detailed Insights From Time-Resolved EPR Spectroscopy. Front Chem 2019; 7:10. [PMID: 30775359 PMCID: PMC6367236 DOI: 10.3389/fchem.2019.00010] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Accepted: 01/07/2019] [Indexed: 11/22/2022] Open
Abstract
Organic photovoltaics (OPV) is a promising technology to account for the increasing demand for energy in form of electricity. Whereas the last decades have seen tremendous progress in the field witnessed by the steady increase in efficiency of OPV devices, we still lack proper understanding of fundamental aspects of light-energy conversion, demanding for systematic investigation on a fundamental level. A detailed understanding of the electronic structure of semiconducting polymers and their building blocks is essential to develop efficient materials for organic electronics. Illuminating conjugated polymers not only leads to excited states, but sheds light on some of the most important aspects of device efficiency in organic electronics as well. The interplay between electronic structure, morphology, flexibility, and local ordering, while at the heart of structure-function relationship of organic electronic materials, is still barely understood. (Time-resolved) electron paramagnetic resonance (EPR) spectroscopy is particularly suited to address these questions, allowing one to directly detect paramagnetic states and to reveal their spin-multiplicity, besides its clearly superior spectral resolution compared to optical methods. This article aims at giving a non-specialist audience an overview of what EPR spectroscopy and particularly its time-resolved variant (TREPR) can contribute to unraveling aspects of structure-function relationship in organic semiconductors.
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Affiliation(s)
- Till Biskup
- Institute of Physical Chemistry, University of Freiburg, Freiburg, Germany
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30
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Lacerda GRDBS, Calado CR, Calado HDR. Electrochromic and electrochemical properties of copolymer films based on EDOT and phenylthiophene derivatives. J Solid State Electrochem 2019. [DOI: 10.1007/s10008-018-04185-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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31
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Molecular assembly of PC70BM with a designed monoporphyrin: Spectroscopic investigation in solution and theoretical calculations. J Mol Liq 2018. [DOI: 10.1016/j.molliq.2018.08.117] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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32
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Kubodera T, Yabusaki M, Rachmat VASA, Cho Y, Yamanari T, Yoshida Y, Kobayashi N, Marumoto K. Operando Direct Observation of Charge Accumulation and the Correlation with Performance Deterioration in PTB7 Polymer Solar Cells. ACS APPLIED MATERIALS & INTERFACES 2018; 10:26434-26442. [PMID: 30001625 DOI: 10.1021/acsami.8b06211] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Polymer solar cells are one of the promising energy sources because of the easy solution-processable production with large area at a low cost without toxicity. Among the polymer materials, a donor-acceptor conjugated copolymer PTB7 has been extensively studied because of the typical high-performance polymer solar cells. Here, we show operando direct observation of charge accumulation in PTB7:PC71BM blend solar cells from a microscopic viewpoint using electron spin resonance spectroscopy. The accumulation of ambipolar charges in the PTB7-based cells is directly observed for the first time, which shows a clear correlation with the performance deterioration during device operation. The sites of the ambipolar charge accumulation are elucidated at the molecular level, whose information would be useful for improving the cell durability in addition to the performance improvement.
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Affiliation(s)
| | | | | | - Yujin Cho
- Semiconductor Device Materials Group, Nano Materials Field , International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS) , 1-1 Namiki , Tsukuba , Ibaraki 305-0044 , Japan
| | - Toshihiro Yamanari
- Research Center for Photovoltaics (RCPV) , National Institute of Advanced Industrial Science and Technology (AIST) , Tsukuba Central 5, 1-1-1 Higashi , Tsukuba , Ibaraki 305-8565 , Japan
| | - Yuji Yoshida
- Research Center for Photovoltaics (RCPV) , National Institute of Advanced Industrial Science and Technology (AIST) , Tsukuba Central 5, 1-1-1 Higashi , Tsukuba , Ibaraki 305-8565 , Japan
| | | | - Kazuhiro Marumoto
- Tsukuba Research Center for Energy Materials Science (TREMS), University of Tsukuba , Tsukuba , Ibaraki 305-8571 , Japan
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33
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Niklas J, Mardis KL, Poluektov OG. Spin Signature of the C 60 Fullerene Anion: A Combined X- and D-Band EPR and DFT Study. J Phys Chem Lett 2018; 9:3915-3921. [PMID: 29969036 PMCID: PMC6563802 DOI: 10.1021/acs.jpclett.8b01613] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Fullerenes attract much attention in various scientific fields, but their electronic properties are still not completely understood. Here we report on a combined EPR and DFT study of the fullerene anion C60- in solid glassy environment. DFT calculations were used to characterize its electronic structure through spin density distribution and magnetic resonance parameters. The electron spin density is not uniformly distributed throughout the C60- cage but shows a pattern similar to PC61BM-. EPR spectroscopy reveals a rhombic g-tensor sensitive to the environment in the frozen glassy solutions, which can be rationalized by deformation of the fullerenes along low-frequency vibrational modes upon cooling. DFT modeling confirms that these deformations lead to variation in the C60- g values. The decrease in g-tensor anisotropy with sample annealing is related to the lessening of g-tensor strain upon temperature relaxation of the most distorted sites in the glassy state.
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Affiliation(s)
- Jens Niklas
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, USA
| | - Kristy L. Mardis
- Department of Chemistry, Physics, and Engineering Studies, Chicago State University, Chicago, Illinois 60628, USA
| | - Oleg G. Poluektov
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, USA
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34
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Ivanov MV, Reid SA, Rathore R. Game of Frontier Orbitals: A View on the Rational Design of Novel Charge-Transfer Materials. J Phys Chem Lett 2018; 9:3978-3986. [PMID: 29952570 DOI: 10.1021/acs.jpclett.8b01093] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Since the first application of frontier molecular orbitals (FMOs) to rationalize stereospecificity of pericyclic reactions, FMOs have remained at the forefront of chemical theory. Yet, the practical application of FMOs in the rational design and synthesis of novel charge transfer materials remains under-appreciated. In this Perspective, we demonstrate that molecular orbital theory is a powerful and universal tool capable of rationalizing the observed redox/optoelectronic properties of various aromatic hydrocarbons in the context of their application as charge-transfer materials. Importantly, the inspection of FMOs can provide instantaneous insight into the interchromophoric electronic coupling and polaron delocalization in polychromophoric assemblies, and therefore is invaluable for the rational design and synthesis of novel materials with tailored properties.
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Affiliation(s)
- Maxim V Ivanov
- Department of Chemistry , Marquette University , P.O. Box 1881, Milwaukee , Wisconsin 53201-1881 , United States
| | - Scott A Reid
- Department of Chemistry , Marquette University , P.O. Box 1881, Milwaukee , Wisconsin 53201-1881 , United States
| | - Rajendra Rathore
- Department of Chemistry , Marquette University , P.O. Box 1881, Milwaukee , Wisconsin 53201-1881 , United States
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35
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Van Landeghem M, Maes W, Goovaerts E, Van Doorslaer S. Disentangling overlapping high-field EPR spectra of organic radicals: Identification of light-induced polarons in the record fullerene-free solar cell blend PBDB-T:ITIC. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2018; 288:1-10. [PMID: 29367021 DOI: 10.1016/j.jmr.2018.01.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Revised: 01/09/2018] [Accepted: 01/10/2018] [Indexed: 06/07/2023]
Abstract
We present a combined high-field EPR and DFT study of light-induced radicals in the bulk heterojunction blend of PBDB-T:ITIC, currently one of the highest efficiency non-fullerene donor:acceptor combinations in organic photovoltaics. We demonstrate two different approaches for disentangling the strongly overlapping high-field EPR spectra of the positive and negative polarons after charge separation: (1) relaxation-filtered field-swept EPR based on the difference in T1 spin-relaxation times and (2) field-swept EDNMR-induced EPR by exploiting the presence of 14N hyperfine couplings in only one of the radical species, the small molecule acceptor radical. The approach is validated by light-induced EPR spectra on related blends and the spectral assignment is underpinned by DFT computations. The broader applicability of the spectral disentangling methods is discussed.
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Affiliation(s)
- Melissa Van Landeghem
- Department of Physics, University of Antwerp, Universiteitsplein 1, 2610 Antwerpen, Belgium.
| | - Wouter Maes
- Institute for Materials Research, Design & Synthesis of Organic Semiconductors, Hasselt University, Agoralaan 1, 3590 Diepenbeek, Belgium.
| | - Etienne Goovaerts
- Department of Physics, University of Antwerp, Universiteitsplein 1, 2610 Antwerpen, Belgium.
| | - Sabine Van Doorslaer
- Department of Physics, University of Antwerp, Universiteitsplein 1, 2610 Antwerpen, Belgium.
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36
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Steyrleuthner R, Zhang Y, Zhang L, Kraffert F, Cherniawski BP, Bittl R, Briseno AL, Bredas JL, Behrends J. Impact of morphology on polaron delocalization in a semicrystalline conjugated polymer. Phys Chem Chem Phys 2018; 19:3627-3639. [PMID: 28094360 DOI: 10.1039/c6cp07485e] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We investigate the delocalization of holes in the semicrystalline conjugated polymer poly(2,5-bis(3-alkylthiophene-2-yl)thieno[3,2-b]thiophene) (PBTTT) by directly measuring the hyperfine coupling between photogenerated polarons and bound nuclear spins using electron nuclear double resonance spectroscopy. An extrapolation of the corresponding oligomer spectra reveals that charges tend to delocalize over 4.0-4.8 nm with delocalization strongly dependent on molecular order and crystallinity of the PBTTT polymer thin films. Density functional theory calculations of hyperfine couplings confirm that long-range corrected functionals appropriately describe the change in coupling strength with increasing oligomer size and agree well with the experimentally measured polymer limit. Our discussion presents general guidelines illustrating the various pitfalls and opportunities when deducing polaron localization lengths from hyperfine coupling spectra of conjugated polymers.
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Affiliation(s)
- Robert Steyrleuthner
- Freie Universität Berlin, Berlin Joint EPR Lab, Institut für Experimentalphysik, Berlin, Germany.
| | - Yuexing Zhang
- King Abdullah University of Science & Technology, Solar & Photovoltaics Engineering Research Center, Thuwal 23955-6900, Saudi Arabia and Department of Chemistry, Hubei University, Wuhan 430062, China
| | - Lei Zhang
- Department of Polymer Science and Engineering, Conte Research Center, University of Massachusetts, 120 Governors Drive, Amherst, MA 01003, USA
| | - Felix Kraffert
- Freie Universität Berlin, Berlin Joint EPR Lab, Institut für Experimentalphysik, Berlin, Germany.
| | - Benjamin P Cherniawski
- Department of Polymer Science and Engineering, Conte Research Center, University of Massachusetts, 120 Governors Drive, Amherst, MA 01003, USA
| | - Robert Bittl
- Freie Universität Berlin, Berlin Joint EPR Lab, Institut für Experimentalphysik, Berlin, Germany.
| | - Alejandro L Briseno
- Department of Polymer Science and Engineering, Conte Research Center, University of Massachusetts, 120 Governors Drive, Amherst, MA 01003, USA
| | - Jean-Luc Bredas
- King Abdullah University of Science & Technology, Solar & Photovoltaics Engineering Research Center, Thuwal 23955-6900, Saudi Arabia
| | - Jan Behrends
- Freie Universität Berlin, Berlin Joint EPR Lab, Institut für Experimentalphysik, Berlin, Germany.
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37
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Lukina EA, Popov AA, Uvarov MN, Suturina EA, Reijerse EJ, Kulik LV. Light-induced charge separation in a P3HT/PC 70BM composite as studied by out-of-phase electron spin echo spectroscopy. Phys Chem Chem Phys 2018; 18:28585-28593. [PMID: 27711566 DOI: 10.1039/c6cp05389k] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
A composite material of semiconducting polymer P3HT and fullerene derivative PC70BM was studied by means of electron spin echo (ESE) spectroscopy. The out-of-phase ESE signal was observed under laser irradiation of the composite at low temperature. We assume that during the charge separation process firstly the spin-correlated radical pairs in the singlet-polarized spin state are formed, and then the net polarization of radical pairs arises due to spin evolution. Both types of polarizations contribute to the out-of-phase ESE signal in the case of non-ideal microwave pulses. Analytical calculation of the echo shape for both types of initial polarization revealed that the contribution of the net polarization becomes zero after averaging over the whole EPR spectrum of the radical pair. This behavior was experimentally confirmed; thus the analysis of the out-of-phase ESE signal was simplified. Interspin distance distributions in the charge transfer state were obtained by modeling the out-of-phase ESE envelope modulation measured at different delays after laser flash TDAF from 300 ns to 3.3 μs at a temperature of 65 K. Due to geminate recombination and diffusion of the radicals from the interface the distribution becomes significantly broader with larger distances prevailing at longer TDAF values. The average distance between charges increases from 3.5 nm to 5.6 nm with an increase in TDAF.
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Affiliation(s)
- Ekaterina A Lukina
- Voevodsky Institute of Chemical Kinetics and Combustion of Siberian Branch of Russian Academy of Sciences, Institutskaya 3, 630090 Novosibirsk, Russia. and Novosibirsk State University, Pirogova 2, 630090 Novosibirsk, Russia
| | - Alexander A Popov
- Voevodsky Institute of Chemical Kinetics and Combustion of Siberian Branch of Russian Academy of Sciences, Institutskaya 3, 630090 Novosibirsk, Russia. and Novosibirsk State University, Pirogova 2, 630090 Novosibirsk, Russia
| | - Mikhail N Uvarov
- Voevodsky Institute of Chemical Kinetics and Combustion of Siberian Branch of Russian Academy of Sciences, Institutskaya 3, 630090 Novosibirsk, Russia.
| | - Elizaveta A Suturina
- Novosibirsk State University, Pirogova 2, 630090 Novosibirsk, Russia and Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, D-45470 Mulheim an der Ruhr, Germany
| | - Edward J Reijerse
- Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, D-45470 Mulheim an der Ruhr, Germany
| | - Leonid V Kulik
- Voevodsky Institute of Chemical Kinetics and Combustion of Siberian Branch of Russian Academy of Sciences, Institutskaya 3, 630090 Novosibirsk, Russia. and Novosibirsk State University, Pirogova 2, 630090 Novosibirsk, Russia
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38
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Naveed KUR, Wang L, Yu H, Ullah RS, Haroon M, Fahad S, Li J, Elshaarani T, Khan RU, Nazir A. Recent progress in the electron paramagnetic resonance study of polymers. Polym Chem 2018. [DOI: 10.1039/c8py00689j] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
This review article provides an overview of the contemporary research based on a tailor-made technique to understand the paramagnetic behavior of different polymer classes.
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Affiliation(s)
| | - Li Wang
- College of Chemical and Biological Engineering
- Zhejiang University
- Zhejiang
- China
| | - Haojie Yu
- College of Chemical and Biological Engineering
- Zhejiang University
- Zhejiang
- China
| | - Raja Summe Ullah
- College of Chemical and Biological Engineering
- Zhejiang University
- Zhejiang
- China
| | - Muhammad Haroon
- College of Chemical and Biological Engineering
- Zhejiang University
- Zhejiang
- China
| | - Shah Fahad
- College of Chemical and Biological Engineering
- Zhejiang University
- Zhejiang
- China
| | - Jiyang Li
- College of Chemical and Biological Engineering
- Zhejiang University
- Zhejiang
- China
| | - Tarig Elshaarani
- College of Chemical and Biological Engineering
- Zhejiang University
- Zhejiang
- China
| | - Rizwan Ullah Khan
- College of Chemical and Biological Engineering
- Zhejiang University
- Zhejiang
- China
| | - Ahsan Nazir
- College of Chemical and Biological Engineering
- Zhejiang University
- Zhejiang
- China
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39
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Thomson SAJ, Niklas J, Mardis KL, Mallares C, Samuel IDW, Poluektov OG. Charge Separation and Triplet Exciton Formation Pathways in Small Molecule Solar Cells as Studied by Time-resolved EPR Spectroscopy. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2017; 121:22707-22719. [PMID: 29606993 PMCID: PMC5875436 DOI: 10.1021/acs.jpcc.7b08217] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Organic solar cells are a promising renewable energy technology, offering the advantages of mechanical flexibility and solution processability. An understanding of the electronic excited states and charge separation pathways in these systems is crucial if efficiencies are to be further improved. Here we use light induced electron paramagnetic resonance (LEPR) spectroscopy and density functional theory calculations (DFT) to study the electronic excited states, charge transfer (CT) dynamics and triplet exciton formation pathways in blends of the small molecule donors (DTS(FBTTh2)2, DTS(F2BTTh2)2, DTS(PTTh2)2, DTG(FBTTh2)2 and DTG(F2BTTh2)2) with the fullerene derivative PC61BM. Using high frequency EPR the g-tensor of the positive polaron on the donor molecules was determined. The experimental results are compared with DFT calculations which reveal that the spin density of the polaron is distributed over a dimer or trimer. Time-resolved EPR (TR-EPR) spectra attributed to singlet CT states were identified and the polarization patterns revealed similar charge separation dynamics in the four fluorobenzothiadiazole donors, while charge separation in the DTS(PTTh2)2 blend is slower. Using TR-EPR we also investigated the triplet exciton formation pathways in the blend. The polarization patterns reveal that the excitons originate from both intersystem crossing (ISC) and back electron transfer (BET) processes. The DTS(PTTh2)2 blend was found to contain substantially more triplet excitons formed by BET than the fluorobenzothiadiazole blends. The higher BET triplet exciton population in the DTS(PTTh2)2 blend is in accordance with the slower charge separation dynamics observed in this blend.
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Affiliation(s)
- Stuart A. J Thomson
- Organic Semiconductor Centre, SUPA, School of Physics & Astronomy, University of St Andrews, St Andrews, KY16 9SS, UK
| | - Jens Niklas
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Kristy L. Mardis
- Department of Chemistry and Physics, Chicago State University, Chicago, Illinois 60628, USA
| | - Christopher Mallares
- Department of Chemistry and Physics, Chicago State University, Chicago, Illinois 60628, USA
| | - Ifor D. W. Samuel
- Organic Semiconductor Centre, SUPA, School of Physics & Astronomy, University of St Andrews, St Andrews, KY16 9SS, UK
- Phone: +44 1334 463114
| | - Oleg G. Poluektov
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
- Phone: +1 630 2523546
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40
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Matsuoka H, Retegan M, Schmitt L, Höger S, Neese F, Schiemann O. Time-Resolved Electron Paramagnetic Resonance and Theoretical Investigations of Metal-Free Room-Temperature Triplet Emitters. J Am Chem Soc 2017; 139:12968-12975. [DOI: 10.1021/jacs.7b04561] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Hideto Matsuoka
- Institute
for Physical and Theoretical Chemistry, University of Bonn, Wegelerstr. 12, 53115 Bonn, Germany
| | - Marius Retegan
- Max Planck Institute for MPI for Chemical Energy Conversion, Stiftstr. 34−36, 45470 Mülheim an der Ruhr, Germany
| | - Lisa Schmitt
- Kekulé
Institute of Organic Chemistry and Biochemistry, University of Bonn, Gerhard-Domagk-Str. 1, 53121 Bonn, Germany
| | - Sigurd Höger
- Kekulé
Institute of Organic Chemistry and Biochemistry, University of Bonn, Gerhard-Domagk-Str. 1, 53121 Bonn, Germany
| | - Frank Neese
- Max Planck Institute for MPI for Chemical Energy Conversion, Stiftstr. 34−36, 45470 Mülheim an der Ruhr, Germany
| | - Olav Schiemann
- Institute
for Physical and Theoretical Chemistry, University of Bonn, Wegelerstr. 12, 53115 Bonn, Germany
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41
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Kraffert F, Bahro D, Meier C, Denne M, Colsmann A, Behrends J. Transport-related triplet states and hyperfine couplings in organic tandem solar cells probed by pulsed electrically detected magnetic resonance spectroscopy. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2017; 282:10-17. [PMID: 28686953 DOI: 10.1016/j.jmr.2017.06.015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2017] [Revised: 06/16/2017] [Accepted: 06/24/2017] [Indexed: 06/07/2023]
Abstract
Tandem solar cells constitute the most successful organic photovoltaic devices with power conversion efficiencies comparable to thin-film silicon solar cells. Especially their high open-circuit voltage - only achievable by a well-adjusted layer stacking - leads to their high efficiencies. Nevertheless, the microscopic processes causing the lossless recombination of charge carriers within the recombination zone are not well understood yet. We show that advanced pulsed electrically detected magnetic resonance techniques such as electrically detected (ED)-Rabi nutation measurements and electrically detected hyperfine sublevel correlation (ED-HYSCORE) spectroscopy help to understand the role of triplet excitons in these microscopic processes. We investigate fully working miniaturised organic tandem solar cells and detect current-influencing doublet states in different layers as well as triplet excitons located on the fullerene-based acceptor. We apply ED-HYSCORE in order to study the nuclear spin environment of the relevant electron/hole spins and detect a significant amount of the low abundant 13C nuclei coupled to the observer spins.
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Affiliation(s)
- Felix Kraffert
- Berlin Joint EPR Lab, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Daniel Bahro
- Light Technology Institute, Karlsruhe Institute of Technology, Engesserstrasse 13, 76131 Karlsruhe, Germany
| | - Christoph Meier
- Berlin Joint EPR Lab, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Maximilian Denne
- Light Technology Institute, Karlsruhe Institute of Technology, Engesserstrasse 13, 76131 Karlsruhe, Germany
| | - Alexander Colsmann
- Light Technology Institute, Karlsruhe Institute of Technology, Engesserstrasse 13, 76131 Karlsruhe, Germany
| | - Jan Behrends
- Berlin Joint EPR Lab, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
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42
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Lukose B, Bobbili SV, Clancy P. Factors affecting tacticity and aggregation of P3HT polymers in P3HT:PCBM blends. MOLECULAR SIMULATION 2017. [DOI: 10.1080/08927022.2017.1303688] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- Binit Lukose
- School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY, USA
| | - Sai Vineeth Bobbili
- School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY, USA
| | - Paulette Clancy
- School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY, USA
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43
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Meyer DL, Lombeck F, Huettner S, Sommer M, Biskup T. Direct S 0→T Excitation of a Conjugated Polymer Repeat Unit: Unusual Spin-Forbidden Transitions Probed by Time-Resolved Electron Paramagnetic Resonance Spectroscopy. J Phys Chem Lett 2017; 8:1677-1682. [PMID: 28345918 DOI: 10.1021/acs.jpclett.7b00644] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
A detailed understanding of the electronic structure of semiconducting polymers and their building blocks is essential to develop efficient materials for organic electronics. (Time-resolved) electron paramagnetic resonance (EPR) is particularly suited to address these questions, allowing one to directly detect paramagnetic states and to reveal their spin-multiplicity, besides its clearly superior resolution compared to optical methods. We present here evidence for a direct S0→T optical excitation of distinct triplet states in the repeat unit of a conjugated polymer used in organic photovoltaics. These states differ in their electronic structure from those populated via intersystem crossing from excited singlet states. This is an additional and so far unconsidered route to triplet states with potentially high impact on efficiency of organic electronic devices.
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Affiliation(s)
| | - Florian Lombeck
- Optoelectronics Group, University of Cambridge , Cavendish Laboratory, Cambridge CB3 0HE, United Kingdom
| | - Sven Huettner
- Organic and Hybrid Electronics, Macromolecular Chemistry I, Universität Bayreuth , 95440 Bayreuth, Germany
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44
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Roy SM, Rao NN, Herissan A, Colbeau-Justin C. Polyaniline film-based wireless photo reactor for hydrogen generation through exciton mediated proton reduction. POLYMER 2017. [DOI: 10.1016/j.polymer.2017.02.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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45
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Kraffert F, Behrends J. Spin-correlated doublet pairs as intermediate states in charge separation processes. Mol Phys 2017. [DOI: 10.1080/00268976.2016.1278479] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
- Felix Kraffert
- Berlin Joint EPR Lab, Fachbereich Physik, Freie Universität Berlin, Berlin, Germany
| | - Jan Behrends
- Berlin Joint EPR Lab, Fachbereich Physik, Freie Universität Berlin, Berlin, Germany
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46
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Liu C, Li Z, Zhang Z, Zhang X, Shen L, Guo W, Zhang L, Long Y, Ruan S. Improving the charge carrier transport of organic solar cells by incorporating a deep energy level molecule. Phys Chem Chem Phys 2017; 19:245-250. [DOI: 10.1039/c6cp07344a] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
A p-type F4-TCNQ molecule was incorporated into the P3HT/ICBA active layer to enhance the device performance of polymer solar cells from 4.50% to 5.83%.
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Affiliation(s)
- Chunyu Liu
- State Key Laboratory on Integrated Optoelectronics
- College of Electronic Science and Engineering
- Jilin University
- Changchun 130012
- People's Republic of China
| | - Zhiqi Li
- State Key Laboratory on Integrated Optoelectronics
- College of Electronic Science and Engineering
- Jilin University
- Changchun 130012
- People's Republic of China
| | - Zhihui Zhang
- State Key Laboratory on Integrated Optoelectronics
- College of Electronic Science and Engineering
- Jilin University
- Changchun 130012
- People's Republic of China
| | - Xinyuan Zhang
- State Key Laboratory on Integrated Optoelectronics
- College of Electronic Science and Engineering
- Jilin University
- Changchun 130012
- People's Republic of China
| | - Liang Shen
- State Key Laboratory on Integrated Optoelectronics
- College of Electronic Science and Engineering
- Jilin University
- Changchun 130012
- People's Republic of China
| | - Wenbin Guo
- State Key Laboratory on Integrated Optoelectronics
- College of Electronic Science and Engineering
- Jilin University
- Changchun 130012
- People's Republic of China
| | - Liu Zhang
- College of Instrumentation & Electrical Engineering
- Jilin University
- Changchun 130061
- People's Republic of China
| | - Yongbing Long
- School of Electronic Engineering
- South China Agricultural University
- Guangzhou
- China
| | - Shengping Ruan
- State Key Laboratory on Integrated Optoelectronics
- College of Electronic Science and Engineering
- Jilin University
- Changchun 130012
- People's Republic of China
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47
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Lukina EA, Suturina E, Reijerse E, Lubitz W, Kulik LV. Spin dynamics of light-induced charge separation in composites of semiconducting polymers and PC60BM revealed using Q-band pulse EPR. Phys Chem Chem Phys 2017; 19:22141-22152. [DOI: 10.1039/c7cp03680a] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Q-Band electron spin echo spectroscopy allows distinguishing light-induced polarons of different types in photovoltaic polymer/fullerene composites.
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Affiliation(s)
- E. A. Lukina
- Voevodsky Institute of Chemical Kinetics and Combustion of Siberian Branch of Russian Academy of Sciences
- 630090 Novosibirsk
- Russia
- Novosibirsk State University
- 630090 Novosibirsk
| | - E. Suturina
- School of Chemistry
- University of Southampton
- Southampton
- UK
| | - E. Reijerse
- Max Planck Institute for Chemical Energy Conversion
- D-45470 Muelheim an der Ruhr
- Germany
| | - W. Lubitz
- Max Planck Institute for Chemical Energy Conversion
- D-45470 Muelheim an der Ruhr
- Germany
| | - L. V. Kulik
- Voevodsky Institute of Chemical Kinetics and Combustion of Siberian Branch of Russian Academy of Sciences
- 630090 Novosibirsk
- Russia
- Novosibirsk State University
- 630090 Novosibirsk
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Kuimov VA, Matveeva EA, Malysheva SF, Samul’tsev DO, Gusarova NK, Khutsishvili SS, Vakul’skaya TI, Trofimov BA. Direct phosphorylation of fullerene C60 with phosphine. DOKLADY CHEMISTRY 2016. [DOI: 10.1134/s0012500816110057] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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49
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Franco Jr. F. Computational study on the structural and optoelectronic properties of a carbazole-benzothiadiazole based conjugated oligomer with various alkyl side-chain lengths. MOLECULAR SIMULATION 2016. [DOI: 10.1080/08927022.2016.1250267] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
- Francisco Franco Jr.
- Chemistry Department, De La Salle University, Manila, Philippines
- Computational Materials Design Research Unit, Center for Natural Sciences and Ecological Research, De La Salle University, Manila, Philippines
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50
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The origin of high PCE in PTB7 based photovoltaics: proper charge neutrality level and free energy of charge separation at PTB7/PC 71BM interface. Sci Rep 2016; 6:35262. [PMID: 27734957 PMCID: PMC5062304 DOI: 10.1038/srep35262] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Accepted: 09/27/2016] [Indexed: 11/08/2022] Open
Abstract
The energy level alignments at donor/acceptor interfaces in organic photovoltaics (OPVs) play a decisive role in device performance. However, little is known about the interfacial energetics in polymer OPVs due to technical issues of the solution process. Here, the frontier ortbial line-ups at the donor/acceptor interface in high performance polymer OPVs, PTB7/PC71BM, were investigated using in situ UPS, XPS and IPES. The evolution of energy levels during PTB7/PC71BM interface formation was investigated using vacuum electrospray deposition, and was compared with that of P3HT/PC61BM. At the PTB7/PC71BM interface, the interface dipole and the band bending were absent due to their identical charge neutrality levels. In contrast, a large interfacial dipole was observed at the P3HT/PC61BM interface. The measured photovoltaic energy gap (EPVG) was 1.10 eV for PTB7/PC71BM and 0.90 eV for P3HT/PC61BM. This difference in the EPVG leads to a larger open-circuit voltage of PTB7/PC71BM than that of P3HT/PC61BM.
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