1
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Gobeze HB, Younus M, Turlington MD, Ahmed S, Schanze KS. Characterization of Excited-State Electronic Structure in Diblock π-Conjugated Oligomers with Adjustable Linker Electronic Coupling. Molecules 2024; 29:2678. [PMID: 38893552 PMCID: PMC11173629 DOI: 10.3390/molecules29112678] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2024] [Revised: 05/21/2024] [Accepted: 05/30/2024] [Indexed: 06/21/2024] Open
Abstract
Diblock conjugated oligomers are π-conjugated molecules that contain two segments having distinct frontier orbital energies and HOMO-LUMO gap offsets. These oligomers are of fundamental interest to understand how the distinct π-conjugated segments interact and modify their excited state properties. The current paper reports a study of two series of diblock oligomers that contain oligothiophene (Tn) and 4,7-bis(2-thienyl)-2,1,3-benzothiadiazole (TBT) segments that are coupled by either ethynyl (-C≡C-) or trans-(-C≡C-)2Pt(II)(PBu3)2 acetylide linkers. In these structures, the Tn segment is electron rich (donor), and the TBT is electron poor (acceptor). The diblock oligomers are characterized by steady-state and time-resolved spectroscopy, including UV-visible absorption, fluorescence, fluorescence lifetimes, and ultrafast transient absorption spectroscopy. Studies are compared in several solvents of different polarity and with different excitation wavelengths. The results reveal that the (-C≡C-) linked oligomers feature a delocalized excited state that takes on a charge transfer (CT) character in more polar media. In the (-C≡C-)2Pt(II)(PBu3)2-linked oligomers, there is weak coupling between the Tn and TBT segments. Consequently, short wavelength excitation selectively excites the Tn segment, which then undergoes ultrafast energy transfer (~1 ps) to afford a TBT-localized excited state.
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Affiliation(s)
| | | | | | | | - Kirk S. Schanze
- Department of Chemistry, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249, USA; (H.B.G.); (M.Y.); (M.D.T.); (S.A.)
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2
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Craig B, Townsend P, de Leon CP, Skylaris CK, Kramer D. An Electronic Structure Investigation of PEDOT with AlCl 4- Anions-A Promising Redox Combination for Energy Storage Applications. Polymers (Basel) 2024; 16:1376. [PMID: 38794569 PMCID: PMC11125351 DOI: 10.3390/polym16101376] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2024] [Revised: 05/01/2024] [Accepted: 05/08/2024] [Indexed: 05/26/2024] Open
Abstract
In this work, we use density functional theory to investigate the electronic structure of poly(3,4-ethylenedioxythiophene) (PEDOT) oligomers with co-located AlCl4- anions, a promising combination for energy storage. The 1980s bipolaron model remains the dominant interpretation of the electronic structure of PEDOT despite recent theoretical progress that has provided new definitions of bipolarons and polarons. By considering the influence of oligomer length, oxidation or anion concentration and spin state, we find no evidence for many of the assertions of the 1980s bipolaron model and so further contribute to a new understanding. No self-localisation of positive charges in PEDOT is found, as predicted by the bipolaron model at the hybrid functional level. Instead, our results show distortions that exhibit a single or a double peak in bond length alternations and charge density. Either can occur at different oxidation or anion concentrations. Rather than representing bipolarons or polaron pairs in the original model, these are electron distributions driven by a range of factors. Distortions can span an arbitrary number of nearby anions. We also contribute a novel conductivity hypothesis. Conductivity in conducting polymers has been observed to reduce at anion concentrations above 0.5. We show that at high anion concentrations, the energy of the localised, non-bonding anionic orbitals approaches that of the system HOMO due to Coulombic repulsion between anions. We hypothesize that with nucleic motion in the macropolymer, these orbitals will interfere with the hopping of charge carriers between sites of similar energy, lowering conductivity.
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Affiliation(s)
- Ben Craig
- School of Engineering, University of Southampton, University Road, Southampton SO17 1BJ, UK (C.P.d.L.)
| | - Peter Townsend
- Department of Chemistry and Chemical Biology, Rutgers University, 123 Bevier Rd., Piscataway, NJ 08854, USA;
| | - Carlos Ponce de Leon
- School of Engineering, University of Southampton, University Road, Southampton SO17 1BJ, UK (C.P.d.L.)
| | - Chris-Kriton Skylaris
- School of Chemistry, University of Southampton, University Road, Southampton SO17 1BJ, UK;
| | - Denis Kramer
- Faculty of Mechanical Engineering, Helmut-Schmidt-University, Holstenhofweg 85, 22043 Hamburg, Germany
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3
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Stewart K, Pagano K, Tan E, Daboczi M, Rimmele M, Luke J, Eslava S, Kim JS. Understanding Effects of Alkyl Side-Chain Density on Polaron Formation Via Electrochemical Doping in Thiophene Polymers. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2211184. [PMID: 37626011 DOI: 10.1002/adma.202211184] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 06/16/2023] [Indexed: 08/27/2023]
Abstract
Polarons exist when charges are injected into organic semiconductors due to their strong coupling with the lattice phonons, significantly affecting electronic charge-transport properties. Understanding the formation and (de)localization of polarons is therefore critical for further developing organic semiconductors as a future electronics platform. However, there are very few studies reported in this area. In particular, there is no direct in situ monitoring of polaron formation and identification of its dependence on molecular structure and impact on electrical properties, limiting further advancement in organic electronics. Herein, how a minor modification of side-chain density in thiophene-based conjugated polymers affects the polaron formation via electrochemical doping, changing the polymers' electrical response to the surrounding dielectric environment for gas sensing, is demonstrated. It is found that the reduction in side-chain density results in a multistep polaron formation, leading to an initial formation of localized polarons in thiophene units without side chains. Reduced side-chain density also allows the formation of a high density of polarons with fewer polymer structural changes. More numerous but more localized polarons generate a stronger analyte response but without the selectivity between polar and non-polar solvents, which is different from the more delocalized polarons that show clear selectivity. The results provide important molecular understanding and design rules for the polaron formation and its impact on electrical properties.
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Affiliation(s)
- Katherine Stewart
- Department of Physics and Centre for Processable Electronics, Imperial College London, London, SW7 2AZ, UK
| | - Katia Pagano
- Department of Physics and Centre for Processable Electronics, Imperial College London, London, SW7 2AZ, UK
| | - Ellasia Tan
- Department of Physics and Centre for Processable Electronics, Imperial College London, London, SW7 2AZ, UK
| | - Matyas Daboczi
- Department of Chemical Engineering and Centre for Processable Electronics, Imperial College London, London, SW7 2AZ, UK
| | - Martina Rimmele
- Department of Chemistry and Centre for Processable Electronics, Imperial College London, London, W12 0BZ, UK
| | - Joel Luke
- Department of Physics and Centre for Processable Electronics, Imperial College London, London, SW7 2AZ, UK
| | - Salvador Eslava
- Department of Chemical Engineering and Centre for Processable Electronics, Imperial College London, London, SW7 2AZ, UK
| | - Ji-Seon Kim
- Department of Physics and Centre for Processable Electronics, Imperial College London, London, SW7 2AZ, UK
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4
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Lee S, Lee J, Sim HR, So C, Chung DS. Shortwave Infrared Organic Photodiodes Realized by Polaron Engineering. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2310250. [PMID: 38016048 DOI: 10.1002/adma.202310250] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Revised: 11/27/2023] [Indexed: 11/30/2023]
Abstract
A novel approach for developing shortwave IR (SWIR) organic photodiodes (OPDs) using doped polymers is presented. SWIR OPDs are challenging to produce because of the limitations in extending the absorption of conjugated molecules and the high dark currents of SWIR-absorbing materials. Herein, it is shown that the conversion of bound polarons to free polarons by light energy can be utilized as an SWIR photodetection mechanism. To maximize the bound-polaron density and bound-to-free polaron ratio of the doped polymer film, the doping process is engineered and dopant molecules are diffused into the crystalline domain of the polymer matrix and a direct correlation between the bound-to-free polaron ratio and device performance is confirmed. The optimized double-doped SWIR OPD exhibits a high external quantum efficiency of 77 100% and specific detectivity of 1.11 × 1011 Jones against SWIR. These findings demonstrate the application potential of polarons as alternatives for Frenkel excitons in SWIR OPDs.
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Affiliation(s)
- Sangjun Lee
- Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea
| | - Juhyeok Lee
- Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea
| | - Hye Ryun Sim
- Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea
| | - Chan So
- Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea
| | - Dae Sung Chung
- Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea
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5
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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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6
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Yan L, Liang Z, Si J, Gong P, Wang Y, Liu X, Tong J, Li J, Hou X. Ultrafast Kinetics of Chlorinated Polymer Donors: A Faster Excitonic Dissociation Path. ACS APPLIED MATERIALS & INTERFACES 2022; 14:6945-6957. [PMID: 35081710 DOI: 10.1021/acsami.1c24348] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Halogen-substituted donor/acceptor materials are widely regarded as a promising strategy toward improved power-conversion efficiencies (PCEs) in polymer solar cells (PSCs). A chlorinated polymer donor, PClBTA-PS, and its non-chlorinated analogue, PBTA-PS, are synthesized. The PClBTA-PS-based devices show significant enhancements in terms of open-circuit voltage (VOC = 0.82 V) and fill factor (FF = 76.20%). In addition, a PCE of 13.20% is obtained, which is significantly higher than that for the PBTA-PS-based devices (PCE = 7.63%). Grazing incident wide-angle X-ray scattering shows that the chlorinated polymer enables better π-π stacking in both pure and blend films. DFT and TD-DFT calculations as well as ultrafast photophysics measurements indicate that chlorinated PClBTA-PS has a smaller bonding energy and a longer spontaneous-emission lifetime. The results also reveal that the charge-transfer-state excitons in PClBTA-PS:IT4Cl blend films split into the charge-separated (CS) state via a faster dissociation path, which produces a higher yield of the CS state. Overall, this study provides a deeper understanding of how a halogen-substituted polymer can improve PSCs in the future.
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Affiliation(s)
- Lihe Yan
- Key Laboratory for Physical Electronics and Devices of the Ministry of Education & Shaanxi Key Lab of Photonic Technique for Information, School of Electronics Science & Engineering, Faculty of Electronic and Information Engineering, Xi'an Jiaotong University, Xi'an 710049, China
| | - Zezhou Liang
- Key Laboratory for Physical Electronics and Devices of the Ministry of Education & Shaanxi Key Lab of Photonic Technique for Information, School of Electronics Science & Engineering, Faculty of Electronic and Information Engineering, Xi'an Jiaotong University, Xi'an 710049, China
| | - Jinhai Si
- Key Laboratory for Physical Electronics and Devices of the Ministry of Education & Shaanxi Key Lab of Photonic Technique for Information, School of Electronics Science & Engineering, Faculty of Electronic and Information Engineering, Xi'an Jiaotong University, Xi'an 710049, China
| | - Pingping Gong
- School of Materials Science and Engineering, Gansu Provincial Engineering Research Center for Organic Semiconductor Materials and Application Technology, Lanzhou Jiaotong University, Lanzhou 730070, China
| | - Yufei Wang
- Siyuan Laboratory, Guangzhou Key Laboratory of Vacuum Coating Technologies and New Energy Materials, Department of Physics, Jinan University, Guangzhou 510632, China
| | - Xingpeng Liu
- School of Materials Science and Engineering, Gansu Provincial Engineering Research Center for Organic Semiconductor Materials and Application Technology, Lanzhou Jiaotong University, Lanzhou 730070, China
| | - Junfeng Tong
- School of Materials Science and Engineering, Gansu Provincial Engineering Research Center for Organic Semiconductor Materials and Application Technology, Lanzhou Jiaotong University, Lanzhou 730070, China
| | - Jianfeng Li
- School of Materials Science and Engineering, Gansu Provincial Engineering Research Center for Organic Semiconductor Materials and Application Technology, Lanzhou Jiaotong University, Lanzhou 730070, China
| | - Xun Hou
- Key Laboratory for Physical Electronics and Devices of the Ministry of Education & Shaanxi Key Lab of Photonic Technique for Information, School of Electronics Science & Engineering, Faculty of Electronic and Information Engineering, Xi'an Jiaotong University, Xi'an 710049, China
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7
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Armstrong ZT, Kunz MB, Zanni MT. Ultrafast Fluctuations in PM6 Domains of Binary and Ternary Organic Photovoltaic Thin Films Probed with Two-Dimensional White-Light Spectroscopy. J Phys Chem Lett 2021; 12:8972-8979. [PMID: 34506148 DOI: 10.1021/acs.jpclett.1c02234] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
We present two-dimensional white-light spectroscopy (2DWL) measurements of binary and ternary bulk heterojunctions of the polymer donor PM6 mixed with state-of-the-art nonfullerene acceptors Y6 or IT4F. The ternary film has a shorter lifetime and faster spectral diffusion than either of the binary films. 2D line shape analysis of the PM6 ground state bleach with a Kubo model determines that all three films have similar amplitudes of fluctuations (Δ = 0.29 fs-1) in their transition frequencies, but different relaxation times (ranging from 102 to 24 fs). The ternary film exhibits faster dynamics than either of the binary films. The short lifetime of the ternary blend is consistent with increased photoexcitation transfer and the fast frequency fluctuations are consistent with structural dynamics of aliphatic side chains. These results suggest that the femtosecond fluctuations of PM6 are impacted by the choice of the acceptor molecules. We hypothesize that those dynamics are either indicative, or perhaps the initial source, of structural dynamics that ultimately contribute to solar cell operation.
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Affiliation(s)
- Zachary T Armstrong
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Miriam Bohlmann Kunz
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Martin T Zanni
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
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8
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Kousseff CJ, Taifakou FE, Neal WG, Palma M, Nielsen CB. Controlling morphology, adhesion, and electrochromic behavior of
PEDOT
films through molecular design and processing. JOURNAL OF POLYMER SCIENCE 2021. [DOI: 10.1002/pol.20210522] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
| | | | - William G. Neal
- Department of Chemistry Queen Mary University of London London UK
| | - Matteo Palma
- Department of Chemistry Queen Mary University of London London UK
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9
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Ghosh R, Paesani F. Unraveling the effect of defects, domain size, and chemical doping on photophysics and charge transport in covalent organic frameworks. Chem Sci 2021; 12:8373-8384. [PMID: 34221318 PMCID: PMC8221171 DOI: 10.1039/d1sc01262b] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Accepted: 05/12/2021] [Indexed: 11/21/2022] Open
Abstract
Understanding the underlying physical mechanisms that govern charge transport in two-dimensional (2D) covalent organic frameworks (COFs) will facilitate the development of novel COF-based devices for optoelectronic and thermoelectric applications. In this context, the low-energy mid-infrared absorption contains valuable information about the structure-property relationships and the extent of intra- and inter-framework "hole" polaron delocalization in doped and undoped polymeric materials. In this study, we provide a quantitative characterization of the intricate interplay between electronic defects, domain sizes, pore volumes, chemical dopants, and three dimensional anisotropic charge migration in 2D COFs. We compare our simulations with recent experiments on doped COF films and establish the correlations between polaron coherence, conductivity, and transport signatures. By obtaining the first quantitative agreement with the measured absorption spectra of iodine doped (aza)triangulene-based COF, we highlight the fundamental differences between the underlying microstructure, spectral signatures, and transport physics of polymers and COFs. Our findings provide conclusive evidence of why iodine doped COFs exhibit lower conductivity compared to doped polythiophenes. Finally, we propose new research directions to address existing limitations and improve charge transport in COFs for applications in functional molecular electronic devices.
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Affiliation(s)
- Raja Ghosh
- Department of Chemistry and Biochemistry, University of California San Diego La Jolla California 92093 USA
| | - Francesco Paesani
- Department of Chemistry and Biochemistry, University of California San Diego La Jolla California 92093 USA
- San Diego Supercomputer Center, University of California San Diego La Jolla California 92093 USA
- Materials Science and Engineering, University of California San Diego La Jolla California 92093 USA
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10
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Tsokkou D, Cheng CY, Krainova N, Mukhopadhyay S, Giebink NC, Banerji N. Ultrafast Charge Transfer Dynamics at the Origin of Photoconductivity in Doped Organic Solids. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2021; 125:7086-7096. [PMID: 33859770 PMCID: PMC8040020 DOI: 10.1021/acs.jpcc.1c01990] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Revised: 03/10/2021] [Indexed: 06/12/2023]
Abstract
In spite of their growing importance for optoelectronic devices, the fundamental properties and photophysics of molecularly doped organic solids remain poorly understood. Such doping typically leads to a small fraction of free conductive charges, with most electronic carriers remaining Coulombically bound to the ionized dopant. Recently, we have reported photocurrent for devices containing vacuum-deposited TAPC (1,1-bis(4-bis(4-methylphenyl)aminophenyl)cyclohexane) doped with MoO3, showing that photoexcitation of charged TAPC molecules increases the concentration of free holes that contribute to conduction. Here, we elucidate the excited-state dynamics of such doped TAPC films to unravel the key mechanisms responsible for this effect. We demonstrate that excitation of different electronic transitions in charged and neutral TAPC molecules allows bound holes to overcome the Coulombic attraction to their MoO3 counterions, resulting in an enhanced yield of long-lived free carriers. This is caused by ultrafast back-and-forth shuffling of charges and excitation energy between adjacent cations and neutral molecules, competing with relatively slow nonradiative decay from higher excited states of TAPC•+. The light-induced generation of conductive carriers requires the coexistence of cationic and neutral TAPC, a favorable energy level alignment, and intermolecular interactions in the solid state.
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Affiliation(s)
- Demetra Tsokkou
- Department
of Chemistry and Biochemistry, University
of Bern, Freiestrasse 3, 3012 Bern, Switzerland
| | - Chiao-Yu Cheng
- Department
of Electrical Engineering, The Pennsylvania
State University, University
Park, Pennsylvania 16802, United States
| | - Nina Krainova
- Department
of Electrical Engineering, The Pennsylvania
State University, University
Park, Pennsylvania 16802, United States
| | - Sukrit Mukhopadhyay
- The
Dow Chemical Company, 1776 Building, Midland, Michigan 48674, United
States
| | - Noel C. Giebink
- Department
of Electrical Engineering, The Pennsylvania
State University, University
Park, Pennsylvania 16802, United States
| | - Natalie Banerji
- Department
of Chemistry and Biochemistry, University
of Bern, Freiestrasse 3, 3012 Bern, Switzerland
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11
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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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12
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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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Peymanfar R, Yektaei M, Javanshir S, Selseleh-Zakerin E. Regulating the energy band-gap, UV–Vis light absorption, electrical conductivity, microwave absorption, and electromagnetic shielding effectiveness by modulating doping agent. POLYMER 2020. [DOI: 10.1016/j.polymer.2020.122981] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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14
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Aubry TJ, Winchell KJ, Salamat CZ, Basile VM, Lindemuth JR, Stauber JM, Axtell JC, Kubena RM, Phan MD, Bird MJ, Spokoyny AM, Tolbert SH, Schwartz BJ. Tunable Dopants with Intrinsic Counterion Separation Reveal the Effects of Electron Affinity on Dopant Intercalation and Free Carrier Production in Sequentially Doped Conjugated Polymer Films. ADVANCED FUNCTIONAL MATERIALS 2020; 30:2001800. [PMID: 32684909 PMCID: PMC7357248 DOI: 10.1002/adfm.202001800] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 04/02/2020] [Accepted: 04/06/2020] [Indexed: 06/11/2023]
Abstract
Carrier mobility in doped conjugated polymers is limited by Coulomb interactions with dopant counterions. This complicates studying the effect of the dopant's oxidation potential on carrier generation because different dopants have different Coulomb interactions with polarons on the polymer backbone. Here, dodecaborane (DDB)-based dopants are used, which electrostatically shield counterions from carriers and have tunable redox potentials at constant size and shape. DDB dopants produce mobile carriers due to spatial separation of the counterion, and those with greater energetic offsets produce more carriers. Neutron reflectometry indicates that dopant infiltration into conjugated polymer films is redox-potential-driven. Remarkably, X-ray scattering shows that despite their large 2-nm size, DDBs intercalate into the crystalline polymer lamellae like small molecules, indicating that this is the preferred location for dopants of any size. These findings elucidate why doping conjugated polymers usually produces integer, rather than partial charge transfer: dopant counterions effectively intercalate into the lamellae, far from the polarons on the polymer backbone. Finally, it is shown that the IR spectrum provides a simple way to determine polaron mobility. Overall, higher oxidation potentials lead to higher doping efficiencies, with values reaching 100% for driving forces sufficient to dope poorly crystalline regions of the film.
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Affiliation(s)
- Taylor J. Aubry
- Department of Chemistry and BiochemistryUniversity of California, Los AngelesLos AngelesCA90095‐1569USA
| | - K. J. Winchell
- Department of Chemistry and BiochemistryUniversity of California, Los AngelesLos AngelesCA90095‐1569USA
| | - Charlene Z. Salamat
- Department of Chemistry and BiochemistryUniversity of California, Los AngelesLos AngelesCA90095‐1569USA
| | - Victoria M. Basile
- Department of Chemistry and BiochemistryUniversity of California, Los AngelesLos AngelesCA90095‐1569USA
| | | | - Julia M. Stauber
- Department of Chemistry and BiochemistryUniversity of California, Los AngelesLos AngelesCA90095‐1569USA
| | - Jonathan C. Axtell
- Department of Chemistry and BiochemistryUniversity of California, Los AngelesLos AngelesCA90095‐1569USA
| | - Rebecca M. Kubena
- Department of Chemistry and BiochemistryUniversity of California, Los AngelesLos AngelesCA90095‐1569USA
| | - Minh D. Phan
- Neutron Scattering DivisionOak Ridge National LaboratoryOak RidgeTN37831USA
| | - Matthew J. Bird
- Chemistry DepartmentBrookhaven National LaboratoryUptonNY11973USA
| | - Alexander M. Spokoyny
- Department of Chemistry and BiochemistryUniversity of California, Los AngelesLos AngelesCA90095‐1569USA
- California NanoSystems InstituteUniversity of California, Los AngelesLos AngelesCA90095‐7227USA
| | - Sarah H. Tolbert
- Department of Chemistry and BiochemistryUniversity of California, Los AngelesLos AngelesCA90095‐1569USA
- California NanoSystems InstituteUniversity of California, Los AngelesLos AngelesCA90095‐7227USA
- Department of Materials Science and EngineeringUniversity of California, Los AngelesLos AngelesCA90095‐1595USA
| | - Benjamin J. Schwartz
- Department of Chemistry and BiochemistryUniversity of California, Los AngelesLos AngelesCA90095‐1569USA
- California NanoSystems InstituteUniversity of California, Los AngelesLos AngelesCA90095‐7227USA
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