1
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Koh QM, Mazlan NS, Seah QJ, Yang JC, Chen YJ, Png RQ, Ho PKH, Chua LL. Effects of Planarization of the Triphenylamine Unit on the Electronic and Transport Properties of Triarylamine-Fluorene Copolymers in Both Doped and Undoped Forms. ACS APPLIED MATERIALS & INTERFACES 2024. [PMID: 39018293 DOI: 10.1021/acsami.4c05254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/19/2024]
Abstract
Triarylamine-alt-fluorene (TAF) copolymers are widely used for hole injection and transport in organic electronics. Despite suggestions to planarize the triphenylamine moiety, little research has been conducted. Here, we report a comprehensive investigation of the effects of planarization on the electronic and transport properties of a model TAF polymer semiconductor core. We compared the conventional twisted-propeller N-4-methoxyphenyl-N,N-diphenylamine-4',4″-diyl (TA) unit and its planarized bridged analogue (bTA) where adjacent o,o'-positions are linked by 1,1-dimethylmethylene. We studied both polyelectrolyte and non-polyelectrolyte forms of this core in both doped and undoped states. We found that planarization leads to an unprecedented trap-free transport of holes, and a pronounced enhancement of their mobility in the undoped state though less so in the doped state. Planarization also induces a slight reduction in the ionization energy of the undoped polymer, consequently lowering the work function of the doped polymer. This is accompanied by small spectral shifts: a red shift in the first absorption band of the undoped polymer and a blue shift in the first absorption band of the polaron. Furthermore, this study unveils new fundamental features of TAF polymers: (i) Doping induces the formation of three polaron bands within the subgap. (ii) Absorption of both neutral and polaron segments exhibit a linear intensity relationship with doping level. (iii) Electrical conductivity reaches a maximum at the half-doped state, varying as σ ∼ (x (1 - x))3 for 0.1 ≲ x ≲ 0.9, where x is the doping level. Finally, we demonstrate the successful integration of these self-compensated hole-doped TAF polymers as efficient hole injection layers in organic semiconductor diodes.
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Affiliation(s)
- Qi-Mian Koh
- Department of Chemistry, National University of Singapore, Lower Kent Ridge Road, S117552 Singapore
| | - Nur Syafiqah Mazlan
- Department of Chemistry, National University of Singapore, Lower Kent Ridge Road, S117552 Singapore
| | - Qiu-Jing Seah
- Department of Chemistry, National University of Singapore, Lower Kent Ridge Road, S117552 Singapore
| | - Jin-Cheng Yang
- Department of Physics, National University of Singapore, Lower Kent Ridge Road, S117550 Singapore
| | - Yue-Jia Chen
- Department of Chemistry, National University of Singapore, Lower Kent Ridge Road, S117552 Singapore
| | - Rui-Qi Png
- Department of Physics, National University of Singapore, Lower Kent Ridge Road, S117550 Singapore
| | - Peter K H Ho
- Department of Physics, National University of Singapore, Lower Kent Ridge Road, S117550 Singapore
| | - Lay-Lay Chua
- Department of Chemistry, National University of Singapore, Lower Kent Ridge Road, S117552 Singapore
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2
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Wu EC, Schwartz BJ. Does the Traditional Band Picture Describe the Electronic Structure of Doped Conjugated Polymers? TD-DFT and Natural Transition Orbital Study of Doped P3HT. J Chem Theory Comput 2023; 19:6761-6769. [PMID: 37769199 DOI: 10.1021/acs.jctc.3c00743] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/30/2023]
Abstract
Polarons and bipolarons are created when one or two electrons are removed from the π-system of a p-type conjugated polymer, respectively. In the traditional band picture, the creation of a polaron causes two electronic energy levels to move into the band gap. The removal of a second electron to form a bipolaron causes the two intragap states to move further into the gap. Several groups, however, who looked at the energies of the Kohn-Sham orbitals from DFT calculations, have recently argued that the traditional band picture is incorrect for explaining the spectroscopy of doped conjugated polymers. Instead, the DFT calculations suggest that polaron creation causes only one unoccupied state to move into the band gap near the valence band edge while half-filled state in the valence band and the conduction band bend downward in energy. To understand the discrepancy, we performed TD-DFT calculations of polarons and bipolarons on poly(3-hexylthiophene) (P3HT). Not only do the TD-DFT-calculated absorption spectra match the experimental absorption spectra, but an analysis using natural transitional orbitals (NTOs), which provides an approximate one-electron picture from the many-electron TD-DFT results, supports the traditional band picture. Our TD-DFT/NTO analysis indicates that the traditional band picture also works for bipolarons, a system for which DFT calculations were unable to determine the electronic structure.
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Affiliation(s)
- Eric C Wu
- Department of Chemistry and Biochemistry University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - Benjamin J Schwartz
- Department of Chemistry and Biochemistry University of California, Los Angeles, Los Angeles, California 90095-1569, United States
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3
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Tang CG, Syafiqah MN, Koh QM, Ang MCY, Choo KK, Sun MM, Callsen M, Feng YP, Chua LL, Png RQ, Ho PKH. Water binding and hygroscopicity in π-conjugated polyelectrolytes. Nat Commun 2023; 14:3978. [PMID: 37407561 DOI: 10.1038/s41467-023-39215-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Accepted: 05/26/2023] [Indexed: 07/07/2023] Open
Abstract
The presence of water strongly influences structure, dynamics and properties of ion-containing soft matter. Yet, the hydration of such matter is not well understood. Here, we show through a large study of monovalent π-conjugated polyelectrolytes that their reversible hydration, up to several water molecules per ion pair, occurs chiefly at the interface between the ion clusters and the hydrophobic matrix without disrupting ion packing. This establishes the appropriate model to be surface hydration, not the often-assumed internal hydration of the ion clusters. Through detailed analysis of desorption energies and O-H vibrational frequencies, together with OPLS4 and DFT calculations, we have elucidated key binding motifs of the sorbed water. Type-I water, which desorbs below 50 °C, corresponds to hydrogen-bonded water clusters constituting secondary hydration. Type-II water, which typically desorbs over 50-150 °C, corresponds to water bound to the anion under the influence of a proximal cation, or to a cation‒anion pair, at the cluster surface. This constitutes primary hydration. Type-III water, which irreversibly desorbs beyond 150 °C, corresponds to water kinetically trapped between ions. Its amount varies strongly with processing and heat treatment. As a consequence, hygroscopicity-which is the water sorption capacity per ion pair-depends not only on the ions, but also their cluster morphology.
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Affiliation(s)
- Cindy Guanyu Tang
- Department of Physics, National University of Singapore, Lower Kent Ridge Road, S117550, Singapore, Singapore
| | - Mazlan Nur Syafiqah
- Department of Chemistry, National University of Singapore, Lower Kent Ridge Road, S117552, Singapore, Singapore
| | - Qi-Mian Koh
- Department of Chemistry, National University of Singapore, Lower Kent Ridge Road, S117552, Singapore, Singapore
| | - Mervin Chun-Yi Ang
- Department of Chemistry, National University of Singapore, Lower Kent Ridge Road, S117552, Singapore, Singapore
| | - Kim-Kian Choo
- Department of Chemistry, National University of Singapore, Lower Kent Ridge Road, S117552, Singapore, Singapore
| | - Ming-Ming Sun
- Department of Chemistry, National University of Singapore, Lower Kent Ridge Road, S117552, Singapore, Singapore
| | - Martin Callsen
- Department of Physics, National University of Singapore, Lower Kent Ridge Road, S117550, Singapore, Singapore
| | - Yuan-Ping Feng
- Department of Physics, National University of Singapore, Lower Kent Ridge Road, S117550, Singapore, Singapore
| | - Lay-Lay Chua
- Department of Chemistry, National University of Singapore, Lower Kent Ridge Road, S117552, Singapore, Singapore.
| | - Rui-Qi Png
- Department of Physics, National University of Singapore, Lower Kent Ridge Road, S117550, Singapore, Singapore.
| | - Peter K H Ho
- Department of Physics, National University of Singapore, Lower Kent Ridge Road, S117550, Singapore, Singapore.
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4
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Wang LX, Tang CG, Tan ZS, Phua HY, Chen J, Lei W, Png RQ, Chua LL, Ho PKH. Double-type-I charge-injection heterostructure for quantum-dot light-emitting diodes. MATERIALS HORIZONS 2022; 9:2147-2159. [PMID: 35616351 DOI: 10.1039/d1mh00859e] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Enforcing balanced electron-hole injection into the emitter layer of quantum-dot light-emitting diodes (QLEDs) remains key to maximizing the quantum efficiency over a wide current density range. This was previously thought not possible for quantum dot (QD) emitters because of their very deep energy bands. Here, we show using Mesolight® blue-emitting CdZnSeS/ZnS QDs as a model that its valence levels are in fact considerably shallower than the corresponding band maximum of the bulk semiconductor, which makes the ideal double-type-I injection/confinement heterostructure accessible using a variety of polymer organic semiconductors as transport and injection layers. We demonstrate flat external quantum efficiency characteristics that indicate near perfect recombination within the QD layer over several decades of current density from the onset of device turn-on of about 10 μA cm-2, for both normal and inverted QLED architectures. We also demonstrate that these organic semiconductors do not chemically degrade the QDs, unlike the usual ZnMgO nanoparticles. However, these more efficient injection heterostructures expose a new vulnerability of the QDs to in device electrochemical degradation. The work here opens a clear path towards next-generation ultra-high-performance, all-solution-processed QLEDs.
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Affiliation(s)
- Li-Xi Wang
- Department of Physics, National University of Singapore, Lower Kent Ridge Road, S117550, Singapore.
- Joint International Research Laboratory of Information Display and Visualization, School of Electronic Science and Engineering, Southeast University, Nanjing, People's Republic of China
| | - Cindy G Tang
- Department of Physics, National University of Singapore, Lower Kent Ridge Road, S117550, Singapore.
| | - Zhao-Siu Tan
- Department of Chemistry, National University of Singapore, Lower Kent Ridge Road, S117552, Singapore.
| | - Hao-Yu Phua
- Department of Physics, National University of Singapore, Lower Kent Ridge Road, S117550, Singapore.
| | - Jing Chen
- Joint International Research Laboratory of Information Display and Visualization, School of Electronic Science and Engineering, Southeast University, Nanjing, People's Republic of China
| | - Wei Lei
- Joint International Research Laboratory of Information Display and Visualization, School of Electronic Science and Engineering, Southeast University, Nanjing, People's Republic of China
| | - Rui-Qi Png
- Department of Physics, National University of Singapore, Lower Kent Ridge Road, S117550, Singapore.
| | - Lay-Lay Chua
- Department of Physics, National University of Singapore, Lower Kent Ridge Road, S117550, Singapore.
- Department of Chemistry, National University of Singapore, Lower Kent Ridge Road, S117552, Singapore.
| | - Peter K H Ho
- Department of Physics, National University of Singapore, Lower Kent Ridge Road, S117550, Singapore.
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5
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Zhang T, Wang F, Kim HB, Choi IW, Wang C, Cho E, Konefal R, Puttisong Y, Terado K, Kobera L, Chen M, Yang M, Bai S, Yang B, Suo J, Yang SC, Liu X, Fu F, Yoshida H, Chen WM, Brus J, Coropceanu V, Hagfeldt A, Brédas JL, Fahlman M, Kim DS, Hu Z, Gao F. Ion-modulated radical doping of spiro-OMeTAD for more efficient and stable perovskite solar cells. Science 2022; 377:495-501. [PMID: 35901165 DOI: 10.1126/science.abo2757] [Citation(s) in RCA: 39] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Record power conversion efficiencies (PCEs) of perovskite solar cells (PSCs) have been obtained with the organic hole transporter 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenyl-amine)9,9'-spirobifluorene (spiro-OMeTAD). Conventional doping of spiro-OMeTAD with hygroscopic lithium salts and volatile 4-tert-butylpyridine is a time-consuming process and also leads to poor device stability. We developed a new doping strategy for spiro-OMeTAD that avoids post-oxidation by using stable organic radicals as the dopant and ionic salts as the doping modulator (referred to as ion-modulated radical doping). We achieved PCEs of >25% and much-improved device stability under harsh conditions. The radicals provide hole polarons that instantly increase the conductivity and work function (WF), and ionic salts further modulate the WF by affecting the energetics of the hole polarons. This organic semiconductor doping strategy, which decouples conductivity and WF tunability, could inspire further optimization in other optoelectronic devices.
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Affiliation(s)
- Tiankai Zhang
- Department of Physics, Chemistry and Biology (IFM), Linköping University, 58183 Linköping, Sweden
| | - Feng Wang
- Department of Physics, Chemistry and Biology (IFM), Linköping University, 58183 Linköping, Sweden
| | - Hak-Beom Kim
- Korea Institute of Energy Research (KIER), Ulsan, Republic of Korea
| | - In-Woo Choi
- Korea Institute of Energy Research (KIER), Ulsan, Republic of Korea
| | - Chuanfei Wang
- Laboratory of Organic Electronics, Department of Science and Technology, Linköping University, 60174 Norrköping, Sweden
| | - Eunkyung Cho
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
| | - Rafal Konefal
- Institute of Macromolecular Chemistry of the Czech Academy of Sciences, 162 06 Prague 6, Czech Republic
| | - Yuttapoom Puttisong
- Department of Physics, Chemistry and Biology (IFM), Linköping University, 58183 Linköping, Sweden
| | - Kosuke Terado
- Graduate School of Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| | - Libor Kobera
- Institute of Macromolecular Chemistry of the Czech Academy of Sciences, 162 06 Prague 6, Czech Republic
| | - Mengyun Chen
- Department of Physics, Chemistry and Biology (IFM), Linköping University, 58183 Linköping, Sweden
| | - Mei Yang
- Department of Physics, Chemistry and Biology (IFM), Linköping University, 58183 Linköping, Sweden
| | - Sai Bai
- Department of Physics, Chemistry and Biology (IFM), Linköping University, 58183 Linköping, Sweden
| | - Bowen Yang
- Laboratory of Photomolecular Science (LSPM), École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.,Department of Chemistry, Ångström Laboratory, Uppsala University, SE-751 20 Uppsala, Sweden
| | - Jiajia Suo
- Laboratory of Photomolecular Science (LSPM), École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.,Department of Chemistry, Ångström Laboratory, Uppsala University, SE-751 20 Uppsala, Sweden
| | - Shih-Chi Yang
- Laboratory for Thin Films and Photovoltaics, Empa-Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Duebendorf, Switzerland
| | - Xianjie Liu
- Laboratory of Organic Electronics, Department of Science and Technology, Linköping University, 60174 Norrköping, Sweden
| | - Fan Fu
- Laboratory for Thin Films and Photovoltaics, Empa-Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Duebendorf, Switzerland
| | - Hiroyuki Yoshida
- Graduate School of Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.,Molecular Chirality Research Center, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| | - Weimin M Chen
- Department of Physics, Chemistry and Biology (IFM), Linköping University, 58183 Linköping, Sweden
| | - Jiri Brus
- Institute of Macromolecular Chemistry of the Czech Academy of Sciences, 162 06 Prague 6, Czech Republic
| | - Veaceslav Coropceanu
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
| | - Anders Hagfeldt
- Laboratory of Photomolecular Science (LSPM), École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.,Department of Chemistry, Ångström Laboratory, Uppsala University, SE-751 20 Uppsala, Sweden
| | - Jean-Luc Brédas
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
| | - Mats Fahlman
- Laboratory of Organic Electronics, Department of Science and Technology, Linköping University, 60174 Norrköping, Sweden
| | - Dong Suk Kim
- Korea Institute of Energy Research (KIER), Ulsan, Republic of Korea
| | - Zhangjun Hu
- Department of Physics, Chemistry and Biology (IFM), Linköping University, 58183 Linköping, Sweden
| | - Feng Gao
- Department of Physics, Chemistry and Biology (IFM), Linköping University, 58183 Linköping, Sweden
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6
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Saeedifard F, Lungwitz D, Yu ZD, Schneider S, Mansour AE, Opitz A, Barlow S, Toney MF, Pei J, Koch N, Marder SR. Use of a Multiple Hydride Donor To Achieve an n-Doped Polymer with High Solvent Resistance. ACS APPLIED MATERIALS & INTERFACES 2022; 14:33598-33605. [PMID: 35822714 DOI: 10.1021/acsami.2c05724] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The ability to insolubilize doped semiconducting polymer layers can help enable the fabrication of efficient multilayer solution-processed electronic and optoelectronic devices. Here, we present a promising approach to simultaneously n-dope and largely insolubilize conjugated polymer films using tetrakis[{4-(1,3-dimethyl-2,3-dihydro-1H-benzo[d]imidazol-2-yl)phenoxy}methyl]methane (tetrakis-O-DMBI-H), which consists of four 2,3-dihydro-1H-benzoimidazole (DMBI-H) n-dopant moieties covalently linked to one another. Doping a thiophene-fused benzodifurandione-based oligo(p-phenylenevinylene)-co-thiophene polymer (TBDOPV-T) with tetrakis-O-DMBI-H results in a highly n-doped film with bulk conductivity of 15 S cm-1. Optical absorption spectra provide evidence for film retention of ∼93% after immersion in o-dichlorobenzene for 5 min. The optical absorption signature of the charge carriers in the n-doped polymer decreases only slightly more than that of the neutral polymer under these conditions, indicating that the exposure to solvent also results in negligible dedoping of the film. Moreover, thermal treatment studies on a tetrakis-O-DMBI-H-doped TBDOPV-T film in contact with another undoped polymer film indicate immobilization of the molecular dopant in TBDOPV-T. This is attributed to the multiple electrostatic interactions between each dopant tetracation and up to four nearby anionic doped polymer segments.
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Affiliation(s)
- Farzaneh Saeedifard
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
- Renewable and Sustainable Energy Institute, University of Colorado Boulder, Boulder, Colorado 80303, United States
| | - Dominique Lungwitz
- Institut für Physik & IRIS Adlershof, Humboldt-Universität zu Berlin, 12489 Berlin, Germany
| | - Zi-Di Yu
- College of Chemistry and Molecular Engineering, Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, Center of Soft Matter Science and Engineering, Peking University, Beijing 100871, China
| | - Sebastian Schneider
- SLAC National Accelerator Laboratory, Stanford Synchrotron Radiation Light Source, Menlo Park, California 94025, United States
- School of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Ahmed E Mansour
- Institut für Physik & IRIS Adlershof, Humboldt-Universität zu Berlin, 12489 Berlin, Germany
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, 12489 Berlin, Germany
| | - Andreas Opitz
- Institut für Physik & IRIS Adlershof, Humboldt-Universität zu Berlin, 12489 Berlin, Germany
| | - Stephen Barlow
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
- Renewable and Sustainable Energy Institute, University of Colorado Boulder, Boulder, Colorado 80303, United States
| | - Michael F Toney
- Renewable and Sustainable Energy Institute, University of Colorado Boulder, Boulder, Colorado 80303, United States
- Department of Chemical and Biological Engineering, University of Colorado Boulder, Boulder, Colorado 80303, United States
| | - Jian Pei
- College of Chemistry and Molecular Engineering, Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, Center of Soft Matter Science and Engineering, Peking University, Beijing 100871, China
| | - Norbert Koch
- Institut für Physik & IRIS Adlershof, Humboldt-Universität zu Berlin, 12489 Berlin, Germany
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, 12489 Berlin, Germany
| | - Seth R Marder
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
- Renewable and Sustainable Energy Institute, University of Colorado Boulder, Boulder, Colorado 80303, United States
- Department of Chemical and Biological Engineering, University of Colorado Boulder, Boulder, Colorado 80303, United States
- Department of Chemistry, University of Colorado Boulder, Boulder, Colorado 80303, United States
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7
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Philipps K, Ie Y, van der Zee B, Png R, Ho PKH, Chua L, del Pino Rosendo E, Ramanan C, Wetzelaer GAH, Blom PWM, Michels JJ. Role of Linker Functionality in Polymers Exhibiting Main-Chain Thermally Activated Delayed Fluorescence. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2022; 9:e2200056. [PMID: 35253396 PMCID: PMC9259719 DOI: 10.1002/advs.202200056] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Revised: 02/12/2022] [Indexed: 05/29/2023]
Abstract
Excellent performance has been reported for organic light-emitting diodes (OLEDs) based on small molecule emitters that exhibit thermally activated delayed fluorescence. However, the necessary vacuum processing makes the fabrication of large-area devices based on these emitters cumbersome and expensive. Here, the authors present high performance OLEDs, based on novel, TADF polymers that can be readily processed from a solution. These polymers are based on the acridine-benzophenone donor-acceptor motif as main-chain TADF chromophores, linked by various conjugated and non-conjugated spacer moieties. The authors' extensive spectroscopic and electronic analysis shows that in particular in case of alkyl spacers, the properties and performance of the monomeric TADF chromophores are virtually left unaffected by the polymerization. They present efficient solution-processed OLEDs based on these TADF polymers, diluted in oligostyrene as a host. The devices based on the alkyl spacer-based TADF polymers exhibit external quantum efficiencies (EQEs) ≈12%, without any outcoupling-enhancing measures. What's more, the EQE of these devices does not drop substantially upon diluting the polymer down to only ten weight percent of active material. In contrast, the EQE of devices based on the monomeric chromophore show significant losses upon dilution due to loss of charge percolation.
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Affiliation(s)
- Kai Philipps
- Max Planck Institute for Polymer ResearchAckermannweg 1055128MainzGermany
| | - Yutaka Ie
- The Institute of Scientific and Industrial Research (ISIR)Osaka University8‐1 MihogaokaIbarakiOsaka567‐0047Japan
| | - Bas van der Zee
- Max Planck Institute for Polymer ResearchAckermannweg 1055128MainzGermany
| | - Rui‐Qi Png
- Department of PhysicsNational University of SingaporeLower Kent Ridge RoadSingaporeS117550Singapore
| | - Peter K. H. Ho
- Department of PhysicsNational University of SingaporeLower Kent Ridge RoadSingaporeS117550Singapore
| | - Lay‐Lay Chua
- Department of PhysicsNational University of SingaporeLower Kent Ridge RoadSingaporeS117550Singapore
- Department of PhysicsNational University of SingaporeLower Kent Ridge RoadSingaporeS117552Singapore
| | | | | | | | - Paul W. M. Blom
- Max Planck Institute for Polymer ResearchAckermannweg 1055128MainzGermany
| | - Jasper J. Michels
- Max Planck Institute for Polymer ResearchAckermannweg 1055128MainzGermany
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8
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Jacobs IE, Lin Y, Huang Y, Ren X, Simatos D, Chen C, Tjhe D, Statz M, Lai L, Finn PA, Neal WG, D'Avino G, Lemaur V, Fratini S, Beljonne D, Strzalka J, Nielsen CB, Barlow S, Marder SR, McCulloch I, Sirringhaus H. High-Efficiency Ion-Exchange Doping of Conducting Polymers. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2102988. [PMID: 34418878 DOI: 10.1002/adma.202102988] [Citation(s) in RCA: 32] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Revised: 06/28/2021] [Indexed: 06/13/2023]
Abstract
Molecular doping-the use of redox-active small molecules as dopants for organic semiconductors-has seen a surge in research interest driven by emerging applications in sensing, bioelectronics, and thermoelectrics. However, molecular doping carries with it several intrinsic problems stemming directly from the redox-active character of these materials. A recent breakthrough was a doping technique based on ion-exchange, which separates the redox and charge compensation steps of the doping process. Here, the equilibrium and kinetics of ion exchange doping in a model system, poly(2,5-bis(3-alkylthiophen-2-yl)thieno(3,2-b)thiophene) (PBTTT) doped with FeCl3 and an ionic liquid, is studied, reaching conductivities in excess of 1000 S cm-1 and ion exchange efficiencies above 99%. Several factors that enable such high performance, including the choice of acetonitrile as the doping solvent, which largely eliminates electrolyte association effects and dramatically increases the doping strength of FeCl3 , are demonstrated. In this high ion exchange efficiency regime, a simple connection between electrochemical doping and ion exchange is illustrated, and it is shown that the performance and stability of highly doped PBTTT is ultimately limited by intrinsically poor stability at high redox potential.
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Affiliation(s)
- Ian E Jacobs
- Optoelectronics Group, Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Yue Lin
- Optoelectronics Group, Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Yuxuan Huang
- Optoelectronics Group, Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Xinglong Ren
- Optoelectronics Group, Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Dimitrios Simatos
- Optoelectronics Group, Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge, CB3 0HE, UK
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
| | - Chen Chen
- Optoelectronics Group, Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Dion Tjhe
- Optoelectronics Group, Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Martin Statz
- Optoelectronics Group, Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Lianglun Lai
- Optoelectronics Group, Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Peter A Finn
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London, E1 4NS, UK
| | - William G Neal
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London, E1 4NS, UK
| | - Gabriele D'Avino
- Grenoble Alpes University, CNRS, Grenoble INP, Institut Néel, 25 rue des Martyrs, Grenoble, 38042, France
| | - Vincent Lemaur
- Laboratory for Chemistry of Novel Materials, University of Mons, Mons, B-7000, Belgium
| | - Simone Fratini
- Grenoble Alpes University, CNRS, Grenoble INP, Institut Néel, 25 rue des Martyrs, Grenoble, 38042, France
| | - David Beljonne
- Laboratory for Chemistry of Novel Materials, University of Mons, Mons, B-7000, Belgium
| | - Joseph Strzalka
- X-Ray Science Division, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - Christian B Nielsen
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London, E1 4NS, UK
| | - Stephen Barlow
- School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Seth R Marder
- School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Iain McCulloch
- KAUST Solar Center, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955, Saudi Arabia
- Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, UK
| | - Henning Sirringhaus
- Optoelectronics Group, Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge, CB3 0HE, UK
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9
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Zozoulenko I, Franco-Gonzalez JF, Gueskine V, Mehandzhiyski A, Modarresi M, Rolland N, Tybrandt K. Electronic, Optical, Morphological, Transport, and Electrochemical Properties of PEDOT: A Theoretical Perspective. Macromolecules 2021. [DOI: 10.1021/acs.macromol.1c00444] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Igor Zozoulenko
- Laboratory of Organic Electronics, ITN, Linköping University, 60174 Norrköping, Sweden
| | | | - Viktor Gueskine
- Laboratory of Organic Electronics, ITN, Linköping University, 60174 Norrköping, Sweden
| | | | - Mohsen Modarresi
- Department of Physics, Ferdowsi University of Mashhad, Mashhad, PO Box 91775-1436, Iran
| | - Nicolas Rolland
- Laboratory of Organic Electronics, ITN, Linköping University, 60174 Norrköping, Sweden
| | - Klas Tybrandt
- Laboratory of Organic Electronics, ITN, Linköping University, 60174 Norrköping, Sweden
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10
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Li JT, Lei T. Recent Progress on Addressing the Key Challenges in Organic Thermoelectrics. Chem Asian J 2021; 16:1508-1518. [PMID: 33915036 DOI: 10.1002/asia.202100285] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2021] [Revised: 04/26/2021] [Indexed: 11/06/2022]
Abstract
Compared with inorganic thermoelectric materials, organic thermoelectric (OTE) materials have attracted increasing attention due to their advantages of low toxicity, high mechanical flexibility, and large-scale solution processability. In the past few years, OTE materials have made remarkable progress in terms of their design, synthesis, and device performance. However, some challenges remain, including the low doping efficiency in n-type materials, poor doping stability with molecular dopants, and the largely reduced Seebeck coefficient after heavily doping, etc. All these factors hinder the further development of OTEs for commercial applications. In this Minireview, we highlight several key challenges during the development of OTEs and summarize recent understandings and efforts to address these challenges.
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Affiliation(s)
- Jia-Tong Li
- Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, School of Materials Science and Engineering, Peking University, Beijing, 100871, P. R. China
| | - Ting Lei
- Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, School of Materials Science and Engineering, Peking University, Beijing, 100871, P. R. China
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11
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Overcoming the water oxidative limit for ultra-high-workfunction hole-doped polymers. Nat Commun 2021; 12:3345. [PMID: 34099650 PMCID: PMC8184950 DOI: 10.1038/s41467-021-23347-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Accepted: 03/23/2021] [Indexed: 11/09/2022] Open
Abstract
It is widely thought that the water-oxidation reaction limits the maximum work function to about 5.25 eV for hole-doped semiconductors exposed to the ambient, constrained by the oxidation potential of air-saturated water. Here, we show that polymer organic semiconductors, when hole-doped, can show work functions up to 5.9 eV, and yet remain stable in the ambient. We further show that de-doping of the polymer is not determined by the oxidation of bulk water, as previously thought, due to its general absence, but by the counter-balancing anion and its ubiquitously hydrated complexes. The effective donor levels of these species, representing the edge of the 'chemical' density of states, can be depressed to about 6.0 eV below vacuum level. This can be achieved by raising the oxidation potential for hydronium generation, using large super-acid anions that are themselves also stable against oxidation. In this way, we demonstrate that poly(fluorene-alt-triarylamine) derivatives with tethered perfluoroalkyl-sulfonylimidosulfonyl anions can provide ambient solution-processability directly in the ultrahigh-workfunction hole-doped state to give films with good thermal stability. These results lay the path for design of soft materials for battery, bio-electronic and thermoelectric applications.
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12
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Improving organic photovoltaic cells by forcing electrode work function well beyond onset of Ohmic transition. Nat Commun 2021; 12:2250. [PMID: 33854070 PMCID: PMC8047006 DOI: 10.1038/s41467-021-22358-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2019] [Accepted: 02/23/2021] [Indexed: 12/03/2022] Open
Abstract
As electrode work function rises or falls sufficiently, the organic semiconductor/electrode contact reaches Fermi-level pinning, and then, few tenths of an electron-volt later, Ohmic transition. For organic solar cells, the resultant flattening of open-circuit voltage (Voc) and fill factor (FF) leads to a ‘plateau’ that maximizes power conversion efficiency (PCE). Here, we demonstrate this plateau in fact tilts slightly upwards. Thus, further driving of the electrode work function can continue to improve Voc and FF, albeit slowly. The first effect arises from the coercion of Fermi level up the semiconductor density-of-states in the case of ‘soft’ Fermi pinning, raising cell built-in potential. The second effect arises from the contact-induced enhancement of majority-carrier mobility. We exemplify these using PBDTTPD:PCBM solar cells, where PBDTTPD is a prototypal face-stacked semiconductor, and where work function of the hole collection layer is systematically ‘tuned’ from onset of Fermi-level pinning, through Ohmic transition, and well into the Ohmic regime. Both open-circuit voltage and fill factor of organic solar cells are affected by the metal-organic semiconductor interface. Here, the authors demonstrate that the voltage can continue to rise when the Fermi level is forced up to the semiconductor density-of-states tail.
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13
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Liang Z, Choi HH, Luo X, Liu T, Abtahi A, Ramasamy US, Hitron JA, Baustert KN, Hempel JL, Boehm AM, Ansary A, Strachan DR, Mei J, Risko C, Podzorov V, Graham KR. n-type charge transport in heavily p-doped polymers. NATURE MATERIALS 2021; 20:518-524. [PMID: 33398117 DOI: 10.1038/s41563-020-00859-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Accepted: 10/20/2020] [Indexed: 06/12/2023]
Abstract
It is commonly assumed that charge-carrier transport in doped π-conjugated polymers is dominated by one type of charge carrier, either holes or electrons, as determined by the chemistry of the dopant. Here, through Seebeck coefficient and Hall effect measurements, we show that mobile electrons contribute substantially to charge-carrier transport in π-conjugated polymers that are heavily p-doped with strong electron acceptors. Specifically, the Seebeck coefficient of several p-doped polymers changes sign from positive to negative as the concentration of the oxidizing agents FeCl3 or NOBF4 increase, and Hall effect measurements for the same p-doped polymers reveal that electrons become the dominant delocalized charge carriers. Ultraviolet and inverse photoelectron spectroscopy measurements show that doping with oxidizing agents results in elimination of the transport gap at high doping concentrations. This approach of heavy p-type doping is demonstrated to provide a promising route to high-performance n-type organic thermoelectric materials.
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Affiliation(s)
- Zhiming Liang
- Department of Chemistry, University of Kentucky, Lexington, Kentucky, USA
| | - Hyun Ho Choi
- Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey, USA
| | - Xuyi Luo
- Department of Chemistry, Purdue University, West Lafayette, Indiana, USA
| | - Tuo Liu
- Department of Chemistry, University of Kentucky, Lexington, Kentucky, USA
| | - Ashkan Abtahi
- Department of Chemistry, University of Kentucky, Lexington, Kentucky, USA
- Department of Physics & Astronomy, University of Kentucky, Lexington, Kentucky, USA
| | - Uma Shantini Ramasamy
- Department of Chemistry, University of Kentucky, Lexington, Kentucky, USA
- Center for Applied Energy Research, University of Kentucky, Lexington, Kentucky, USA
| | | | - Kyle N Baustert
- Department of Chemistry, University of Kentucky, Lexington, Kentucky, USA
| | - Jacob L Hempel
- Department of Physics & Astronomy, University of Kentucky, Lexington, Kentucky, USA
| | - Alex M Boehm
- Department of Chemistry, University of Kentucky, Lexington, Kentucky, USA
| | - Armin Ansary
- Department of Physics & Astronomy, University of Kentucky, Lexington, Kentucky, USA
| | - Douglas R Strachan
- Department of Physics & Astronomy, University of Kentucky, Lexington, Kentucky, USA
| | - Jianguo Mei
- Department of Chemistry, Purdue University, West Lafayette, Indiana, USA
| | - Chad Risko
- Department of Chemistry, University of Kentucky, Lexington, Kentucky, USA
- Center for Applied Energy Research, University of Kentucky, Lexington, Kentucky, USA
| | - Vitaly Podzorov
- Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey, USA
| | - Kenneth R Graham
- Department of Chemistry, University of Kentucky, Lexington, Kentucky, USA.
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14
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Ding Y, Yang C, Huang C, Lu Y, Yao Z, Pan C, Wang J, Pei J. Thermally Activated n‐Doping of Organic Semiconductors Achieved by N‐Heterocyclic Carbene Based Dopant. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202011537] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Yi‐Fan Ding
- Beijing National Laboratory for Molecular Sciences (BNLMS) Key Laboratory of Polymer Chemistry and Physics of Ministry of, Education Center of Soft Matter Science and Engineering College of Chemistry and Molecular Engineering Peking University Beijing 100871 China
| | - Chi‐Yuan Yang
- Beijing National Laboratory for Molecular Sciences (BNLMS) Key Laboratory of Polymer Chemistry and Physics of Ministry of, Education Center of Soft Matter Science and Engineering College of Chemistry and Molecular Engineering Peking University Beijing 100871 China
| | - Chun‐Xi Huang
- Beijing National Laboratory for Molecular Sciences (BNLMS) Key Laboratory of Polymer Chemistry and Physics of Ministry of, Education Center of Soft Matter Science and Engineering College of Chemistry and Molecular Engineering Peking University Beijing 100871 China
| | - Yang Lu
- Beijing National Laboratory for Molecular Sciences (BNLMS) Key Laboratory of Polymer Chemistry and Physics of Ministry of, Education Center of Soft Matter Science and Engineering College of Chemistry and Molecular Engineering Peking University Beijing 100871 China
| | - Ze‐Fan Yao
- Beijing National Laboratory for Molecular Sciences (BNLMS) Key Laboratory of Polymer Chemistry and Physics of Ministry of, Education Center of Soft Matter Science and Engineering College of Chemistry and Molecular Engineering Peking University Beijing 100871 China
| | - Chen‐Kai Pan
- Beijing National Laboratory for Molecular Sciences (BNLMS) Key Laboratory of Polymer Chemistry and Physics of Ministry of, Education Center of Soft Matter Science and Engineering College of Chemistry and Molecular Engineering Peking University Beijing 100871 China
| | - Jie‐Yu Wang
- Beijing National Laboratory for Molecular Sciences (BNLMS) Key Laboratory of Polymer Chemistry and Physics of Ministry of, Education Center of Soft Matter Science and Engineering College of Chemistry and Molecular Engineering Peking University Beijing 100871 China
| | - Jian Pei
- Beijing National Laboratory for Molecular Sciences (BNLMS) Key Laboratory of Polymer Chemistry and Physics of Ministry of, Education Center of Soft Matter Science and Engineering College of Chemistry and Molecular Engineering Peking University Beijing 100871 China
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15
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Oh S, Nikolaev A, Tagami K, Tran T, Lee D, Mukherjee S, Segalman RA, Han S, Read de Alaniz J, Chabinyc ML. Redox-Active Polymeric Ionic Liquids with Pendant N-Substituted Phenothiazine. ACS APPLIED MATERIALS & INTERFACES 2021; 13:5319-5326. [PMID: 33480673 DOI: 10.1021/acsami.0c20462] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Polymers that are elastic while supporting charge transport are desirable for flexible and soft electronics. Many polymers with bulky and conjugated redox-active pendant units have high glass transition temperatures (Tg) in their neutral form that will not lead to elasticity at room temperature. Their behavior in charged form in the solid state without an electrolyte has not been extensively studied. Here, the design strategy of polymeric ionic liquid where two weakly interacting ionic groups are used to maintain a low Tg is shown to lead to flexible redox active polymers. The use of a flexible ethylene backbone and redox-active phenothiazine (PTZ)-based pendant group resulted in polymers with relatively low Tg that are electrically conductive. PTZ that was N-substituted with 2-(2-ethoxyethoxy)ethoxy)ethyl was found to promote solubility of the polymer and lower the Tg of the neutral polymer by ∼150 °C relative to that of the Tg of a variant without the N-substituent. Doping with trifluoromethanesulfonimide leads to an electrically conductive polymer without significantly increasing the Tg. Physical characterization by UV-vis-NIR spectroscopy, electron spin resonance spectroscopy, and impedance spectroscopy verified that the molecular design leads to an efficient charge hopping between the PTZ groups.
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Affiliation(s)
- Saejin Oh
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California 93106, United States
| | - Andrei Nikolaev
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California 93106, United States
| | - Kan Tagami
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California 93106, United States
| | - Thi Tran
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California 93106, United States
| | - Dongwook Lee
- Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, California 93106, United States
- California NanoSystems Institute, University of California, Santa Barbara, Santa Barbara, California 93106, United States
| | - Sanjoy Mukherjee
- Materials Department, University of California, Santa Barbara, Santa Barbara, California 93106, United States
| | - Rachel A Segalman
- Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, California 93106, United States
- Materials Department, University of California, Santa Barbara, Santa Barbara, California 93106, United States
| | - Songi Han
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California 93106, United States
- Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, California 93106, United States
| | - Javier Read de Alaniz
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California 93106, United States
| | - Michael L Chabinyc
- Materials Department, University of California, Santa Barbara, Santa Barbara, California 93106, United States
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16
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Watanabe S, Hakamatani R, Yaegashi K, Yamashita Y, Nozawa H, Sasaki M, Kumagai S, Okamoto T, Tang CG, Chua L, Ho PKH, Takeya J. Surface Doping of Organic Single-Crystal Semiconductors to Produce Strain-Sensitive Conductive Nanosheets. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2021; 8:2002065. [PMID: 33552854 PMCID: PMC7856890 DOI: 10.1002/advs.202002065] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Revised: 09/24/2020] [Indexed: 06/12/2023]
Abstract
A highly periodic electrostatic potential, even though established in van der Waals bonded organic crystals, is essential for the realization of a coherent band electron system. While impurity doping is an effective chemical operation that can precisely tune the energy of an electronic system, it always faces an unavoidable difficulty in molecular crystals because the introduction of a relatively high density of dopants inevitably destroys the highly ordered molecular framework. In striking contrast, a versatile strategy is presented to create coherent 2D electronic carriers at the surface of organic semiconductor crystals with their precise molecular structures preserved perfectly. The formation of an assembly of redox-active molecular dopants via a simple one-shot solution process on a molecularly flat crystalline surface allows efficient chemical doping and results in a relatively high carrier density of 1013 cm-2 at room temperature. Structural and magnetotransport analyses comprehensively reveal that excellent carrier transport and piezoresistive effects can be obtained that are similar to those in bulk crystals.
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Affiliation(s)
- Shun Watanabe
- Material Innovation Research Center (MIRC) and Department of Advanced Materials ScienceGraduate School of Frontier SciencesThe University of Tokyo5‐1‐5 KashiwanohaKashiwaChiba277‐8561Japan
- AIST‐UTokyo Advanced Operando‐Mesurement Technology Open Innovation Laboratory (OPERANDO‐OIL)AIST5‐1‐5 KashiwanohaKashiwaChiba277‐8561Japan
- Precursory Research for Embryonic Science and Technology (PRESTO)4‐1‐8 HonchoKawaguchiSaitama332‐0012Japan
| | - Ryohei Hakamatani
- Material Innovation Research Center (MIRC) and Department of Advanced Materials ScienceGraduate School of Frontier SciencesThe University of Tokyo5‐1‐5 KashiwanohaKashiwaChiba277‐8561Japan
| | - Keita Yaegashi
- Material Innovation Research Center (MIRC) and Department of Advanced Materials ScienceGraduate School of Frontier SciencesThe University of Tokyo5‐1‐5 KashiwanohaKashiwaChiba277‐8561Japan
| | - Yu Yamashita
- Material Innovation Research Center (MIRC) and Department of Advanced Materials ScienceGraduate School of Frontier SciencesThe University of Tokyo5‐1‐5 KashiwanohaKashiwaChiba277‐8561Japan
- International Center of Materials Nanoarchitectonics (WPI‐MANA)National Institute for Materials Science (NIMS)1‐1 NamikiTsukuba305‐0044Japan
| | - Han Nozawa
- PI‐CRYSTAL Inc.5‐4‐19 KashiwanohaKashiwaChiba277‐0882Japan
| | - Mari Sasaki
- Material Innovation Research Center (MIRC) and Department of Advanced Materials ScienceGraduate School of Frontier SciencesThe University of Tokyo5‐1‐5 KashiwanohaKashiwaChiba277‐8561Japan
| | - Shohei Kumagai
- Material Innovation Research Center (MIRC) and Department of Advanced Materials ScienceGraduate School of Frontier SciencesThe University of Tokyo5‐1‐5 KashiwanohaKashiwaChiba277‐8561Japan
| | - Toshihiro Okamoto
- Material Innovation Research Center (MIRC) and Department of Advanced Materials ScienceGraduate School of Frontier SciencesThe University of Tokyo5‐1‐5 KashiwanohaKashiwaChiba277‐8561Japan
- AIST‐UTokyo Advanced Operando‐Mesurement Technology Open Innovation Laboratory (OPERANDO‐OIL)AIST5‐1‐5 KashiwanohaKashiwaChiba277‐8561Japan
- Precursory Research for Embryonic Science and Technology (PRESTO)4‐1‐8 HonchoKawaguchiSaitama332‐0012Japan
| | - Cindy G. Tang
- Department of PhysicsNational University of SingaporeLower Kent Ridge RoadSingaporeS117550Singapore
| | - Lay‐Lay Chua
- Department of PhysicsNational University of SingaporeLower Kent Ridge RoadSingaporeS117550Singapore
- Department of ChemistryNational University of SingaporeLower Kent Ridge RoadSingaporeS1175502Singapore
| | - Peter K. H. Ho
- Department of PhysicsNational University of SingaporeLower Kent Ridge RoadSingaporeS117550Singapore
| | - Jun Takeya
- Material Innovation Research Center (MIRC) and Department of Advanced Materials ScienceGraduate School of Frontier SciencesThe University of Tokyo5‐1‐5 KashiwanohaKashiwaChiba277‐8561Japan
- AIST‐UTokyo Advanced Operando‐Mesurement Technology Open Innovation Laboratory (OPERANDO‐OIL)AIST5‐1‐5 KashiwanohaKashiwaChiba277‐8561Japan
- International Center of Materials Nanoarchitectonics (WPI‐MANA)National Institute for Materials Science (NIMS)1‐1 NamikiTsukuba305‐0044Japan
- PI‐CRYSTAL Inc.5‐4‐19 KashiwanohaKashiwaChiba277‐0882Japan
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17
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Ding Y, Yang C, Huang C, Lu Y, Yao Z, Pan C, Wang J, Pei J. Thermally Activated n‐Doping of Organic Semiconductors Achieved by N‐Heterocyclic Carbene Based Dopant. Angew Chem Int Ed Engl 2021; 60:5816-5820. [DOI: 10.1002/anie.202011537] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2020] [Revised: 11/23/2020] [Indexed: 11/07/2022]
Affiliation(s)
- Yi‐Fan Ding
- Beijing National Laboratory for Molecular Sciences (BNLMS) Key Laboratory of Polymer Chemistry and Physics of Ministry of, Education Center of Soft Matter Science and Engineering College of Chemistry and Molecular Engineering Peking University Beijing 100871 China
| | - Chi‐Yuan Yang
- Beijing National Laboratory for Molecular Sciences (BNLMS) Key Laboratory of Polymer Chemistry and Physics of Ministry of, Education Center of Soft Matter Science and Engineering College of Chemistry and Molecular Engineering Peking University Beijing 100871 China
| | - Chun‐Xi Huang
- Beijing National Laboratory for Molecular Sciences (BNLMS) Key Laboratory of Polymer Chemistry and Physics of Ministry of, Education Center of Soft Matter Science and Engineering College of Chemistry and Molecular Engineering Peking University Beijing 100871 China
| | - Yang Lu
- Beijing National Laboratory for Molecular Sciences (BNLMS) Key Laboratory of Polymer Chemistry and Physics of Ministry of, Education Center of Soft Matter Science and Engineering College of Chemistry and Molecular Engineering Peking University Beijing 100871 China
| | - Ze‐Fan Yao
- Beijing National Laboratory for Molecular Sciences (BNLMS) Key Laboratory of Polymer Chemistry and Physics of Ministry of, Education Center of Soft Matter Science and Engineering College of Chemistry and Molecular Engineering Peking University Beijing 100871 China
| | - Chen‐Kai Pan
- Beijing National Laboratory for Molecular Sciences (BNLMS) Key Laboratory of Polymer Chemistry and Physics of Ministry of, Education Center of Soft Matter Science and Engineering College of Chemistry and Molecular Engineering Peking University Beijing 100871 China
| | - Jie‐Yu Wang
- Beijing National Laboratory for Molecular Sciences (BNLMS) Key Laboratory of Polymer Chemistry and Physics of Ministry of, Education Center of Soft Matter Science and Engineering College of Chemistry and Molecular Engineering Peking University Beijing 100871 China
| | - Jian Pei
- Beijing National Laboratory for Molecular Sciences (BNLMS) Key Laboratory of Polymer Chemistry and Physics of Ministry of, Education Center of Soft Matter Science and Engineering College of Chemistry and Molecular Engineering Peking University Beijing 100871 China
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18
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Voss MG, Challa JR, Scholes DT, Yee PY, Wu EC, Liu X, Park SJ, León Ruiz O, Subramaniyan S, Chen M, Jenekhe SA, Wang X, Tolbert SH, Schwartz BJ. Driving Force and Optical Signatures of Bipolaron Formation in Chemically Doped Conjugated Polymers. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2000228. [PMID: 33296113 DOI: 10.1002/adma.202000228] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 10/11/2020] [Indexed: 06/12/2023]
Abstract
Molecular dopants are often added to semiconducting polymers to improve electrical conductivity. However, the use of such dopants does not always produce mobile charge carriers. In this work, ultrafast spectroscopy is used to explore the nature of the carriers created following doping of conjugated push-pull polymers with both F4 TCNQ (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) and FeCl3 . It is shown that for one particular push-pull material, the charge carriers created by doping are entirely non-conductive bipolarons and not single polarons, and that transient absorption spectroscopy following excitation in the infrared can readily distinguish the two types of charge carriers. Based on density functional theory calculations and experiments on multiple push-pull conjugated polymers, it is argued that the size of the donor push units determines the relative stabilities of polarons and bipolarons, with larger donor units stabilizing the bipolarons by providing more area for two charges to co-reside.
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Affiliation(s)
- Matthew G Voss
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
| | - J Reddy Challa
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
| | - D Tyler Scholes
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
| | - Patrick Y Yee
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
| | - Eric C Wu
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
| | - Xiao Liu
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
| | - Sanghyun J Park
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
| | - Omar León Ruiz
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
| | - Selvam Subramaniyan
- Department of Chemical Engineering and Department of Chemistry, University of Washington, Seattle, WA, 98195-1750, USA
| | - Mengdan Chen
- Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials, Key Laboratory of Cluster Science of Ministry of Education, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing, 100081, China
| | - Samson A Jenekhe
- Department of Chemical Engineering and Department of Chemistry, University of Washington, Seattle, WA, 98195-1750, USA
| | - Xiaolin Wang
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
- Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials, Key Laboratory of Cluster Science of Ministry of Education, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing, 100081, China
| | - Sarah H Tolbert
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
- California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA, 90095-8352, USA
- Department of Materials Science and Engineering, University of California, Los Angeles, Los Angeles, CA, 90095-1595, USA
| | - Benjamin J Schwartz
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095-1569, USA
- California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA, 90095-8352, USA
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19
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Sahalianov I, Hynynen J, Barlow S, Marder SR, Müller C, Zozoulenko I. UV-to-IR Absorption of Molecularly p-Doped Polythiophenes with Alkyl and Oligoether Side Chains: Experiment and Interpretation Based on Density Functional Theory. J Phys Chem B 2020; 124:11280-11293. [PMID: 33237790 PMCID: PMC7872427 DOI: 10.1021/acs.jpcb.0c08757] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 11/04/2020] [Indexed: 11/28/2022]
Abstract
The UV-to-IR transitions in p-doped poly(3-hexylthiophene) (P3HT) with alkyl side chains and polar polythiophene with tetraethylene glycol side chains are studied experimentally by means of the absorption spectroscopy and computationally using density functional theory (DFT) and tight-binding DFT. The evolution of electronic structure is calculated as the doping level is varied, while the roles of dopant ions, chain twisting, and π-π stacking are also considered, each of these having the effect of broadening the absorption peaks while not significantly changing their positions. The calculated spectra are found to be in good agreement with experimental spectra obtained for the polymers doped with a molybdenum dithiolene complex. As in other DFT studies of doped conjugated polymers, the electronic structure and assignment of optical transitions that emerge are qualitatively different from those obtained through earlier "traditional" approaches. In particular, the two prominent bands seen for the p-doped materials are present for both polarons and bipolarons/polaron pairs. The lowest energy of these transitions is due to excitation from the valence band to a spin-resolved orbitals located in the gap between the bands. The higher-energy band is a superposition of excitation from the valence band to a spin-resolved orbitals in the gap and an excitation between bands.
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Affiliation(s)
- Ihor Sahalianov
- Laboratory
of Organic Electronics, Department of Science and Technology, Linköping University, 60174 Norrköping, Sweden
| | - Jonna Hynynen
- Department
of Chemistry and Chemical Engineering, Chalmers
University of Technology, 41296 Göteborg, Sweden
| | - 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
| | - Christian Müller
- Department
of Chemistry and Chemical Engineering, Chalmers
University of Technology, 41296 Göteborg, Sweden
| | - Igor Zozoulenko
- Laboratory
of Organic Electronics, Department of Science and Technology, Linköping University, 60174 Norrköping, Sweden
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20
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Wegner B, Lungwitz D, Mansour AE, Tait CE, Tanaka N, Zhai T, Duhm S, Forster M, Behrends J, Shoji Y, Opitz A, Scherf U, List‐Kratochvil EJW, Fukushima T, Koch N. An Organic Borate Salt with Superior p-Doping Capability for Organic Semiconductors. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2020; 7:2001322. [PMID: 32995128 PMCID: PMC7507313 DOI: 10.1002/advs.202001322] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Revised: 05/12/2020] [Indexed: 06/02/2023]
Abstract
Molecular doping allows enhancement and precise control of electrical properties of organic semiconductors, and is thus of central technological relevance for organic (opto-) electronics. Beyond single-component molecular electron acceptors and donors, organic salts have recently emerged as a promising class of dopants. However, the pertinent fundamental understanding of doping mechanisms and doping capabilities is limited. Here, the unique capabilities of the salt consisting of a borinium cation (Mes2B+; Mes: mesitylene) and the tetrakis(penta-fluorophenyl)borate anion [B(C6F5)4]- is demonstrated as p-type dopant for polymer semiconductors. With a range of experimental methods, the doping mechanism is identified to comprise electron transfer from the polymer to Mes2B+, and the positive charge on the polymer is stabilized by [B(C6F5)4]-. Notably, the former salt cation leaves during processing and is not present in films. The anion [B(C6F5)4]- even enables the stabilization of polarons and bipolarons in poly(3-hexylthiophene), not yet achieved with other molecular dopants. From doping studies with high ionization energy polymer semiconductors, the effective electron affinity of Mes2B+[B(C6F5)4]- is estimated to be an impressive 5.9 eV. This significantly extends the parameter space for doping of polymer semiconductors.
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Affiliation(s)
- Berthold Wegner
- Institut für Physik and IRIS AdlershofHumboldt‐Universität zu BerlinBerlinD‐12489Germany
- Helmholtz‐Zentrum Berlin für Materialien und Energie GmbHBerlinD‐12489Germany
| | - Dominique Lungwitz
- Institut für Physik and IRIS AdlershofHumboldt‐Universität zu BerlinBerlinD‐12489Germany
| | - Ahmed E. Mansour
- Institut für Physik and IRIS AdlershofHumboldt‐Universität zu BerlinBerlinD‐12489Germany
- Helmholtz‐Zentrum Berlin für Materialien und Energie GmbHBerlinD‐12489Germany
| | - Claudia E. Tait
- Berlin Joint EPR LabFachbereich PhysikFreie Universität BerlinBerlinD‐14195Germany
| | - Naoki Tanaka
- Laboratory for Chemistry and Life ScienceInstitute of Innovative ResearchTokyo Institute of TechnologyYokohama226‐8503Japan
| | - Tianshu Zhai
- Institute of Functional Nano and Soft Materials (FUNSOM)Jiangsu Key Laboratory for Carbon‐Based Functional Materials and Devices and Joint International Research Laboratory of Carbon‐Based Functional Materials and DevicesSoochow UniversitySuzhou215123P. R. China
| | - Steffen Duhm
- Institute of Functional Nano and Soft Materials (FUNSOM)Jiangsu Key Laboratory for Carbon‐Based Functional Materials and Devices and Joint International Research Laboratory of Carbon‐Based Functional Materials and DevicesSoochow UniversitySuzhou215123P. R. China
| | - Michael Forster
- Makromolekulare Chemie and Institut für PolymertechnologieBergische Universität WuppertalWuppertalD‐42097Germany
| | - Jan Behrends
- Berlin Joint EPR LabFachbereich PhysikFreie Universität BerlinBerlinD‐14195Germany
| | - Yoshiaki Shoji
- Laboratory for Chemistry and Life ScienceInstitute of Innovative ResearchTokyo Institute of TechnologyYokohama226‐8503Japan
| | - Andreas Opitz
- Institut für Physik and IRIS AdlershofHumboldt‐Universität zu BerlinBerlinD‐12489Germany
| | - Ullrich Scherf
- Makromolekulare Chemie and Institut für PolymertechnologieBergische Universität WuppertalWuppertalD‐42097Germany
| | - Emil J. W. List‐Kratochvil
- Institut für Physik and IRIS AdlershofHumboldt‐Universität zu BerlinBerlinD‐12489Germany
- Helmholtz‐Zentrum Berlin für Materialien und Energie GmbHBerlinD‐12489Germany
- Institut für ChemieHumboldt‐Universität zu BerlinBerlinD‐12489Germany
| | - Takanori Fukushima
- Laboratory for Chemistry and Life ScienceInstitute of Innovative ResearchTokyo Institute of TechnologyYokohama226‐8503Japan
| | - Norbert Koch
- Institut für Physik and IRIS AdlershofHumboldt‐Universität zu BerlinBerlinD‐12489Germany
- Helmholtz‐Zentrum Berlin für Materialien und Energie GmbHBerlinD‐12489Germany
- Institute of Functional Nano and Soft Materials (FUNSOM)Jiangsu Key Laboratory for Carbon‐Based Functional Materials and Devices and Joint International Research Laboratory of Carbon‐Based Functional Materials and DevicesSoochow UniversitySuzhou215123P. R. China
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21
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Ou Y, Wang A, Zhang F, Hu F. Dendritic Groups Substituted Kekulé‐Benzene‐Bridged Bis(triarylamine) Mixed‐valence Systems: Syntheses, Characterization and Electronic Coupling Properties. ChemistrySelect 2020. [DOI: 10.1002/slct.202000158] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Ya‐Ping Ou
- College of Chemistry and Material ScienceHengyang Normal University, Key Laboratory of Functional Metal-Organic Compounds of Hunan Province, Key Laboratory of Functional Organometallic Materials of Hunan Province College, Hengyang Hunan 421008 P.R. China
| | - Aihui Wang
- College of Chemistry and Material ScienceHengyang Normal University, Key Laboratory of Functional Metal-Organic Compounds of Hunan Province, Key Laboratory of Functional Organometallic Materials of Hunan Province College, Hengyang Hunan 421008 P.R. China
| | - Fuxing Zhang
- College of Chemistry and Material ScienceHengyang Normal University, Key Laboratory of Functional Metal-Organic Compounds of Hunan Province, Key Laboratory of Functional Organometallic Materials of Hunan Province College, Hengyang Hunan 421008 P.R. China
| | - Fang Hu
- Faculty of Materials Science and Chemical EngineeringNingbo University Ningbo 315211 China
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22
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Teo DWY, Jamal Z, Phua HY, Tang CG, Png RQ, Chua LL. Nearly 100% Photocrosslinking Efficiency in Ultrahigh Work Function Hole-Doped Conjugated Polymers Using Bis(fluorophenyl azide) Additives. ACS APPLIED MATERIALS & INTERFACES 2019; 11:48103-48112. [PMID: 31786924 DOI: 10.1021/acsami.9b12503] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Self-compensated (SC) hole-doped conjugated polyelectrolytes with high work functions can provide efficient hole-injection and -collection layers for organic and other semiconductor devices. If these films can be photocrosslinked, the semiconductor overlayer can be deposited from a wider range of solvents, enabling flexibility in device design and fabrication. However, a generic photocrosslinking methodology for these materials is not yet available. Here, we demonstrate that sFPA82-TfO, the recently developed bis(fluorophenyl azide) photocrosslinker that is also i-line compatible, can surprisingly give 100% efficient photocrosslinking for SC hole-doped conjugated polyelectrolytes, i.e., one crosslink per reactive moiety, using mTFF-C2F5SIS-Na, a triarylamine-fluorene copolymer, as the model polyelectrolyte, without degrading its ultrahigh work function of 5.75 eV. The photocrosslinking efficiency is much higher than in the corresponding undoped polyelectrolyte and nonconjugated polyelectrolyte films, where the efficiency is only 20%. We attribute this improvement to the formation of smaller ion multiplet clusters in the hole-doped polyelectrolyte, as suggested by molecular dynamics simulations and infrared spectroscopy, which prevents occlusion of the ionic crosslinker. Photocrosslinking of the SC hole-doped mTFF-C2F5SIS-Na film used as a hole-injection layer in 100 nm-thick PFOP diodes suppresses the leakage current by over 3 orders of magnitude compared to those without crosslinking, to below 30 nA cm-2 at ±2 V. Photocrosslinking of the same film used as the hole-collection layer in PBDTTPD:PC61BM solar cells produces a higher photocurrent density, fill factor, and power conversion efficiency.
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Affiliation(s)
- Desmond W Y Teo
- Department of Chemistry , National University of Singapore , Lower Kent Ridge Road , S117552 Singapore
| | - Zaini Jamal
- Department of Chemistry , National University of Singapore , Lower Kent Ridge Road , S117552 Singapore
| | - Hao-Yu Phua
- Department of Physics , National University of Singapore , Lower Kent Ridge Road , S117550 Singapore
| | - Cindy G Tang
- Department of Physics , National University of Singapore , Lower Kent Ridge Road , S117550 Singapore
| | - Rui-Qi Png
- Department of Physics , National University of Singapore , Lower Kent Ridge Road , S117550 Singapore
| | - Lay-Lay Chua
- Department of Chemistry , National University of Singapore , Lower Kent Ridge Road , S117552 Singapore
- Department of Physics , National University of Singapore , Lower Kent Ridge Road , S117550 Singapore
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23
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Tan A, Zhang P. Tailoring the growth and electronic structures of organic molecular thin films. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:503001. [PMID: 31422957 DOI: 10.1088/1361-648x/ab3c22] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
In the rapidly developing electronics industry, it has become increasingly necessary to explore materials that are cheap, flexible and versatile which have led to significant research efforts towards organic molecular thin films. Organic molecules are unique compared to their inorganic atomic counterparts as their properties can be tuned drastically through chemical functionalization, offering versatility, though their extended shape and weak intermolecular interactions bring significant challenges to the control of both the growth and the electronic structures of molecular thin films. In this paper, we will review the self-assembly process and how to establish long-range ordered organic molecular thin films. We will also discuss how the electronic structures of thin films are impacted by the molecule's local electrostatic environment and its interaction with the substrate, within the context of controlling interfacial energy level alignment between organic semiconductors and electrodes in electronic devices.
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Affiliation(s)
- Andrew Tan
- Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, United States of America
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24
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Tang CG, Syafiqah MN, Koh QM, Zhao C, Zaini J, Seah QJ, Cass MJ, Humphries MJ, Grizzi I, Burroughes JH, Png RQ, Chua LL, Ho PKH. Multivalent anions as universal latent electron donors. Nature 2019; 573:519-525. [PMID: 31554981 DOI: 10.1038/s41586-019-1575-7] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Accepted: 07/08/2019] [Indexed: 11/09/2022]
Abstract
Electrodes with low work functions are required to efficiently inject electrons into semiconductor devices. However, when the work function drops below about 4 electronvolts, the electrode suffers oxidation in air, which prevents its fabrication in ambient conditions. Here we show that multivalent anions such as oxalate, carbonate and sulfite can act as powerful latent electron donors when dispersed as small ion clusters in a matrix, while retaining their ability to be processed in solution in ambient conditions. The anions in these clusters can even n-dope the semiconductor core of π-conjugated polyelectrolytes that have low electron affinities, through a ground-state doping mechanism that is further amplified by a hole-sensitized or photosensitized mechanism in the device. A theoretical analysis of donor levels of these anions reveals that they are favourably upshifted from ionic lattices by a decrease in the Coulomb stabilization of small ion clusters, and by irreversibility effects. We attain an ultralow effective work function of 2.4 electronvolts with the polyfluorene core. We realize high-performance, solution-processed, white-light-emitting diodes and organic solar cells using polymer electron injection layers with these universal anion donors, demonstrating a general approach to chemically designed and ambient-processed Ohmic electron contacts for semiconductor devices.
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Affiliation(s)
- Cindy G Tang
- Department of Physics, National University of Singapore, Singapore, Singapore
| | - Mazlan Nur Syafiqah
- Department of Chemistry, National University of Singapore, Singapore, Singapore
| | - Qi-Mian Koh
- Department of Chemistry, National University of Singapore, Singapore, Singapore
| | - Chao Zhao
- Department of Physics, National University of Singapore, Singapore, Singapore
| | - Jamal Zaini
- Department of Chemistry, National University of Singapore, Singapore, Singapore
| | - Qiu-Jing Seah
- Department of Chemistry, National University of Singapore, Singapore, Singapore
| | | | | | - Ilaria Grizzi
- Cambridge Display Technology Limited, Godmanchester, UK
| | | | - Rui-Qi Png
- Department of Physics, National University of Singapore, Singapore, Singapore.
| | - Lay-Lay Chua
- Department of Physics, National University of Singapore, Singapore, Singapore. .,Department of Chemistry, National University of Singapore, Singapore, Singapore.
| | - Peter K H Ho
- Department of Physics, National University of Singapore, Singapore, Singapore
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25
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Yamashita Y, Tsurumi J, Ohno M, Fujimoto R, Kumagai S, Kurosawa T, Okamoto T, Takeya J, Watanabe S. Efficient molecular doping of polymeric semiconductors driven by anion exchange. Nature 2019; 572:634-638. [DOI: 10.1038/s41586-019-1504-9] [Citation(s) in RCA: 126] [Impact Index Per Article: 25.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Accepted: 06/20/2019] [Indexed: 12/25/2022]
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26
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Christiansen DT, Tomlinson AL, Reynolds JR. New Design Paradigm for Color Control in Anodically Coloring Electrochromic Molecules. J Am Chem Soc 2019; 141:3859-3862. [DOI: 10.1021/jacs.9b01507] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Dylan T. Christiansen
- School of Chemistry and Biochemistry, School of Materials Science and Engineering, Center for Organic Photonics and Electronics, Georgia Tech Polymer Network, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Aimée L. Tomlinson
- Department of Chemistry/Biochemistry, University of North Georgia, Dahlonega, Georgia 30597, United States
| | - John R. Reynolds
- School of Chemistry and Biochemistry, School of Materials Science and Engineering, Center for Organic Photonics and Electronics, Georgia Tech Polymer Network, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
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27
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Yan H, Tang Y, Meng X, Xiao T, Lu G, Ma W. Achieving High Doping Concentration by Dopant Vapor Deposition in Organic Solar Cells. ACS APPLIED MATERIALS & INTERFACES 2019; 11:4178-4184. [PMID: 30623646 DOI: 10.1021/acsami.8b16162] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Compared with the interfacial doping, molecular doping in bulk heterojunction (BHJ) is a more direct but challenging approach to optimize the photovoltaic performance in organic solar cells (OSCs). One of the main obstacles for its success is the low doping concentration because of the morphological damage. Starting from the phase diagram analysis, we discover that the unpreferred good miscibility between the p-type dopant and the acceptor leads to incorrect dopant dispersion, which reduces the achievable doping content. To overcome this, we use sequential doping by vapor annealing instead of blend solution doping, and we achieve the high doping concentration without sacrificing the blend film morphology. Benefiting from the undamaged film, we fulfill improved photovoltaic performance. Our positive results reveal the feasibility of high-level doping in complex organic BHJ films. It is believed that doping at high concentration potentially enlarges the extent of tunable range on electronic properties in OSCs and indicates greater improvement for device performance.
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Affiliation(s)
- Han Yan
- State Key Laboratory for Mechanical Behavior of Materials , Xi'an Jiaotong University , Xi'an 710049 , P. R. China
| | - Yabing Tang
- State Key Laboratory for Mechanical Behavior of Materials , Xi'an Jiaotong University , Xi'an 710049 , P. R. China
| | - Xiangyi Meng
- State Key Laboratory for Mechanical Behavior of Materials , Xi'an Jiaotong University , Xi'an 710049 , P. R. China
| | - Tong Xiao
- Frontier Institute of Science and Technology , Xi'an Jiaotong University , Xi'an 710054 , P. R. China
| | - Guanghao Lu
- Frontier Institute of Science and Technology , Xi'an Jiaotong University , Xi'an 710054 , P. R. China
| | - Wei Ma
- State Key Laboratory for Mechanical Behavior of Materials , Xi'an Jiaotong University , Xi'an 710049 , P. R. China
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28
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Voss MG, Scholes DT, Challa JR, Schwartz BJ. Ultrafast transient absorption spectroscopy of doped P3HT films: distinguishing free and trapped polarons. Faraday Discuss 2019; 216:339-362. [PMID: 31038132 DOI: 10.1039/c8fd00210j] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
It is generally presumed that the vast majority of carriers created by chemical doping of semiconducting polymer films are coulombically trapped by the counteranion, with only a small fraction that are free and responsible for the increased conductivity essential for organic electronic applications. At higher doping levels, it is also possible for bipolarons to form, which are expected to be less conductive than single polarons. Unfortunately, there is no simple way to distinguish free polarons, trapped polarons and bipolarons using steady-state spectroscopy. Thus, in this work, we use ultrafast transient absorption spectroscopy to study the dynamics of polarons in 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TNCQ)-doped films of poly(3-hexylthiophene-2,5-diyl) (P3HT) as a function of dopant concentration and excitation wavelength. When exciting on the red side of the polaron P1 transition, our transient absorption spectra and kinetics match well with what is expected for free 2-D-delocalized polarons; the measurements are not consistent with a recent theory of doped conjugated polymer electronic structure that suggests that the half-filled state lies deeper in the conduction band rather than in the bandgap. As we tune the excitation wavelength to the blue, our measurements reveal an increasing amount of slower transient kinetics that are consistent with the presence of coulombically-trapped polarons rather than bipolarons. Taking advantage of their distinct ultrafast relaxation kinetics as a type of action spectroscopy, we are able to extract the steady-state absorption spectra of free and trapped polarons as a function of dopant concentration. By comparing the results to theoretical models, we determine that in F4TCNQ-doped P3HT films, trapped polarons sit ∼0.4 nm away from the anion while free polarons reside between 0.7 and 0.9 nm from the counteranion. Perhaps counterintuitively, the ratio of trapped to free polarons increases at higher doping levels, an observation that is consistent with a plateau in the concentration-dependent conductivity of F4TCNQ-doped P3HT films.
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Affiliation(s)
- Matthew G Voss
- Department of Chemistry and Biochemistry, University of California Los Angeles (UCLA), Los Angeles, CA 90095-1569, USA.
| | - D Tyler Scholes
- Department of Chemistry and Biochemistry, University of California Los Angeles (UCLA), Los Angeles, CA 90095-1569, USA.
| | - J Reddy Challa
- Department of Chemistry and Biochemistry, University of California Los Angeles (UCLA), Los Angeles, CA 90095-1569, USA.
| | - Benjamin J Schwartz
- Department of Chemistry and Biochemistry, University of California Los Angeles (UCLA), Los Angeles, CA 90095-1569, USA.
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29
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Tan JK, Png RQ, Zhao C, Ho PKH. Ohmic transition at contacts key to maximizing fill factor and performance of organic solar cells. Nat Commun 2018; 9:3269. [PMID: 30111794 PMCID: PMC6093871 DOI: 10.1038/s41467-018-05200-w] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Accepted: 06/12/2018] [Indexed: 11/27/2022] Open
Abstract
While thermodynamic detailed balance limits the maximum power conversion efficiency of a solar cell, the quality of its contacts can further limit the actual efficiency. The criteria for good contacts to organic semiconductors, however, are not well understood. Here, by tuning the work function of poly(3,4-ethylenedioxythiophene) hole collection layers in fine steps across the Fermi-level pinning threshold of the model photoactive layer, poly(3-hexylthiophene):phenyl-C61-butyrate methyl ester, in organic solar cells, we obtain direct evidence for a non-ohmic to ohmic transition at the hole contact that lies 0.3 eV beyond its Fermi-level pinning transition. This second transition corresponds to reduction of the photocurrent extraction resistance below the bulk resistance of the cell. Current detailed balance analysis reveals that this extraction resistance is the counterpart of injection resistance, and the measured characteristics are manifestations of charge carrier hopping across the interface. Achieving ohmic transition at both contacts is key to maximizing fill factor without compromising open-circuit voltage nor short-circuit current of the solar cell. The importance of ohmic contacts for organic solar cells has been recognized, but how the transition to ohmic behavior occurs is unknown. Tan et al. show that this transition happens separately beyond Fermi-level pinning, when the interfacial contact resistivity becomes sufficiently low.
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Affiliation(s)
- Jun-Kai Tan
- Department of Physics, National University of Singapore, Lower Kent Ridge Road, Singapore, S117550, Singapore.,Solar Energy Research Institute of Singapore, National University of Singapore, Engineering Drive 1, Singapore, S117574, Singapore
| | - Rui-Qi Png
- Department of Physics, National University of Singapore, Lower Kent Ridge Road, Singapore, S117550, Singapore.,Solar Energy Research Institute of Singapore, National University of Singapore, Engineering Drive 1, Singapore, S117574, Singapore
| | - Chao Zhao
- Department of Physics, National University of Singapore, Lower Kent Ridge Road, Singapore, S117550, Singapore.,Solar Energy Research Institute of Singapore, National University of Singapore, Engineering Drive 1, Singapore, S117574, Singapore
| | - Peter K H Ho
- Department of Physics, National University of Singapore, Lower Kent Ridge Road, Singapore, S117550, Singapore. .,Solar Energy Research Institute of Singapore, National University of Singapore, Engineering Drive 1, Singapore, S117574, Singapore.
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30
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Jacobs IE, Moulé AJ. Controlling Molecular Doping in Organic Semiconductors. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2017; 29:1703063. [PMID: 28921668 DOI: 10.1002/adma.201703063] [Citation(s) in RCA: 177] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Revised: 07/24/2017] [Indexed: 05/23/2023]
Abstract
The field of organic electronics thrives on the hope of enabling low-cost, solution-processed electronic devices with mechanical, optoelectronic, and chemical properties not available from inorganic semiconductors. A key to the success of these aspirations is the ability to controllably dope organic semiconductors with high spatial resolution. Here, recent progress in molecular doping of organic semiconductors is summarized, with an emphasis on solution-processed p-type doped polymeric semiconductors. Highlighted topics include how solution-processing techniques can control the distribution, diffusion, and density of dopants within the organic semiconductor, and, in turn, affect the electronic properties of the material. Research in these areas has recently intensified, thanks to advances in chemical synthesis, improved understanding of charged states in organic materials, and a focus on relating fabrication techniques to morphology. Significant disorder in these systems, along with complex interactions between doping and film morphology, is often responsible for charge trapping and low doping efficiency. However, the strong coupling between doping, solubility, and morphology can be harnessed to control crystallinity, create doping gradients, and pattern polymers. These breakthroughs suggest a role for molecular doping not only in device function but also in fabrication-applications beyond those directly analogous to inorganic doping.
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Affiliation(s)
- Ian E Jacobs
- Department of Materials Science, University of California, Davis, 1 Shields Avenue, Davis, CA, 95616, USA
| | - Adam J Moulé
- Department of Chemical Engineering, University of California, Davis, 1 Shields Avenue, Davis, CA, 95616, USA
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31
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Tang CG, Ang MCY, Choo KK, Keerthi V, Tan JK, Syafiqah MN, Kugler T, Burroughes JH, Png RQ, Chua LL, Ho PKH. Doped polymer semiconductors with ultrahigh and ultralow work functions for ohmic contacts. Nature 2016; 539:536-540. [DOI: 10.1038/nature20133] [Citation(s) in RCA: 151] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Accepted: 10/03/2016] [Indexed: 01/26/2023]
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