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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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Cation exchange behavior during the redox switching of poly (3,4-ethylenedioxythiophene) films. J Solid State Electrochem 2020. [DOI: 10.1007/s10008-020-04809-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
AbstractPoly (3,4-ethylenedioxythiophene), PEDOT, films were synthesized at room temperature by potentiodynamic and potentiostatic step deposition in aqueous solutions containing EDOT monomer and LiClO4. In some solutions, the effect of small amounts of sodium dodecylsulfate, SDS, on the polymerization rate of EDOT and on the stiffness of the obtained PEDOT film was studied. The obtained PEDOT films were transferred in aqueous solutions containing cations with different molar mass, such as H+, Li+, Na+, K+, and Cs+. The apparent molar masses of the exchanged species during potentiodynamic experiments were determined by in situ microgravimetry. These measurements underlined the importance of the electrolyte chosen for electropolymerization process. It is known that SDS anions can be trapped inside the polymer layer during electropolymerization, providing them with a cation exchange behavior. However, even if the PEDOT films were deposited from an electrolyte without SDS, they still acted as cation exchangers.
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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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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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Takeda N, Miller JR. Poly(3-decylthiophene) radical anions and cations in solution: single and multiple polarons and their delocalization lengths in conjugated polymers. J Phys Chem B 2012; 116:14715-23. [PMID: 23157495 DOI: 10.1021/jp3096242] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Optical absorption spectra of anions and cations of poly(3-decylthiophene) (P3DT) in solution were identified as single polarons. Pulse radiolysis of P3DT in THF determined the spatial extent of one negative polaron to be ~11.5 thiophene units by observing transient absorption of P3DT(-•) radical ions, which are prinicpally free ions, at 850 nm with ε = (7.25 ± 0.47) × 10(4) M(-1) cm(-1) and bleaching of the neutral absorption band at 450 nm. P3DT(-•) was formed in a combination of diffusive reactions and fast "step" processes. Similarly, a positive polaron of P3DT was estimated to delocalize over ~8.7 thiophene units by pulse radiolysis in chloroform. Chemical reduction by sodium and oxidation by FeCl(3) injected multiple charges into a single P3DT chain while showing absorption spectra in the early stages of reaction resembling those observed by pulse radiolysis. The results indicated that multiple polarons exist in a single chain of P3DT before coalescing into bipolarons or transforming into other forms of polaron.
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Affiliation(s)
- Norihiko Takeda
- Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA
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Savenije TJ, Sperlich A, Kraus H, Poluektov O, Heeney M, Dyakonov V. Observation of bi-polarons in blends of conjugated copolymers and fullerene derivatives. Phys Chem Chem Phys 2011; 13:16579-84. [DOI: 10.1039/c1cp21607d] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Yamamoto T. Synthesis of π-Conjugated Polymers by Organometallic Polycondensation. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2010. [DOI: 10.1246/bcsj.20090338] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Dennany L, Innis PC, Wallace GG, Forster RJ. Reversible Photoinduced Electron Transfer in a Ruthenium Poly(2-methoxyaniline-5-sulfonic acid) Composite Film. J Phys Chem B 2008; 112:12907-12. [DOI: 10.1021/jp804213r] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Lynn Dennany
- Intelligent Polymer Research Institute and ARC Centre of Excellence for Electromaterials Science, University of Wollongong, Northfields Avenue, Wollongong NSW 2522, Australia, and Biomedical Diagnostics Institute, National Centre for Sensor Research, School of Chemical Sciences, Dublin City University, Dublin 9, Ireland
| | - Peter C. Innis
- Intelligent Polymer Research Institute and ARC Centre of Excellence for Electromaterials Science, University of Wollongong, Northfields Avenue, Wollongong NSW 2522, Australia, and Biomedical Diagnostics Institute, National Centre for Sensor Research, School of Chemical Sciences, Dublin City University, Dublin 9, Ireland
| | - Gordon G. Wallace
- Intelligent Polymer Research Institute and ARC Centre of Excellence for Electromaterials Science, University of Wollongong, Northfields Avenue, Wollongong NSW 2522, Australia, and Biomedical Diagnostics Institute, National Centre for Sensor Research, School of Chemical Sciences, Dublin City University, Dublin 9, Ireland
| | - Robert J. Forster
- Intelligent Polymer Research Institute and ARC Centre of Excellence for Electromaterials Science, University of Wollongong, Northfields Avenue, Wollongong NSW 2522, Australia, and Biomedical Diagnostics Institute, National Centre for Sensor Research, School of Chemical Sciences, Dublin City University, Dublin 9, Ireland
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