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Xu Y, Yan J, Zhou W, Ouyang J. Development of High Performance Thermoelectric Polymers via Doping or Dedoping Engineering. Chem Asian J 2024; 19:e202400329. [PMID: 38736306 DOI: 10.1002/asia.202400329] [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: 03/25/2024] [Revised: 05/11/2024] [Accepted: 05/12/2024] [Indexed: 05/14/2024]
Abstract
It is of great significance to develop high-performance thermoelectric (TE) materials, because they can be used to harvest waste heat into electricity and there is abundant waste heat on earth. The conventional TE materials are inorganic semimetals or semiconductors like Bi2Te3 and its derivatives. However, they have problems of high cost, scarce/toxic elements, high thermal conductivity, and poor mechanical flexibility. Organic TE materials emerged as the next-generation TE materials because of their merits including solution processability, low cost, abundant element, low intrinsic thermal conductivity, and high mechanical flexibility. Organic TE materials are mainly conducting polymers because of their high conductivity. Both the conductivity and Seebeck coefficient depend on the doping level, and they are interdependent. Hence, the TE properties of polymers can be improved through doping/dedoping engineering. There are three types of doping forms, oxidative (or reductive) doping, protonic acid doping, and charge transfer doping. Accordingly, they can be dedoped by different approaches. In this article, we review the methods to dope and dedope p-type and n-type TE polymers and the combination of doping and dedoping to optimize their TE properties. Secondary doping is also covered, since it can significantly enhance the conductivity of some TE polymers.
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Affiliation(s)
- Yichen Xu
- National University of Singapore (Suzhou) Research Institute, No. 377 Linquan Street, Suzhou Industrial Park, Suzhou, Jiangsu, 215123, China
- Department of Materials Science and Engineering, National University of Singapore, Singapore, 117574, China
| | - Jin Yan
- National University of Singapore (Suzhou) Research Institute, No. 377 Linquan Street, Suzhou Industrial Park, Suzhou, Jiangsu, 215123, China
| | - Wei Zhou
- National University of Singapore (Suzhou) Research Institute, No. 377 Linquan Street, Suzhou Industrial Park, Suzhou, Jiangsu, 215123, China
| | - Jianyong Ouyang
- National University of Singapore (Suzhou) Research Institute, No. 377 Linquan Street, Suzhou Industrial Park, Suzhou, Jiangsu, 215123, China
- Department of Materials Science and Engineering, National University of Singapore, Singapore, 117574, China
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Wu Y, Salamat CZ, León Ruiz A, Simafranca AF, Akmanşen-Kalayci N, Wu EC, Doud E, Mehmedović Z, Lindemuth JR, Phan MD, Spokoyny AM, Schwartz BJ, Tolbert SH. Using Bulky Dodecaborane-Based Dopants to Produce Mobile Charge Carriers in Amorphous Semiconducting Polymers. CHEMISTRY OF MATERIALS : A PUBLICATION OF THE AMERICAN CHEMICAL SOCIETY 2024; 36:5552-5562. [PMID: 38883433 PMCID: PMC11171275 DOI: 10.1021/acs.chemmater.4c00502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/22/2024] [Revised: 04/19/2024] [Accepted: 04/22/2024] [Indexed: 06/18/2024]
Abstract
Conjugated polymers are a versatile class of electronic materials featured in a variety of next-generation electronic devices. The utility of such polymers is contingent in large part on their electrical conductivity, which depends both on the density of charge carriers (polarons) and on the carrier mobility. Carrier mobility, in turn, is largely controlled by the separation between the polarons and dopant counterions, as counterions can produce Coulombic traps. In previous work, we showed that large dopants based on dodecaborane (DDB) clusters were able to reduce Coulombic binding and thus increase carrier mobility in regioregular (RR) poly(3-hexylthiophene-2,5-diyl) (P3HT). Here, we use a DDB-based dopant to study the effects of polaron-counterion separation in chemically doped regiorandom (RRa) P3HT, which is highly amorphous. X-ray scattering shows that the DDB dopants, despite their large size, can partially order the RRa P3HT during doping and produce a doped polymer crystal structure similar to that of DDB-doped RR P3HT; Alternating Field (AC) Hall measurements also confirm a similar hole mobility. We also show that use of the large DDB dopants successfully reduces Coulombic binding of polarons and counterions in amorphous polymer regions, resulting in a 77% doping efficiency in RRa P3HT films. The DDB dopants are able to produce RRa P3HT films with a 4.92 S/cm conductivity, a value that is ∼200× higher than that achieved with 3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), the traditional dopant molecule. These results show that tailoring dopants to produce mobile carriers in both the amorphous and semicrystalline regions of conjugated polymers is an effective strategy for increasing achievable polymer conductivities, particularly in low-cost polymers with random regiochemistry. The results also emphasize the importance of dopant size and shape for producing Coulombically unbound, mobile polarons capable of electrical conduction in less-ordered materials.
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Affiliation(s)
- Yutong Wu
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California 90095-1569, United States
| | - Charlene Z Salamat
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California 90095-1569, United States
| | - Alex León Ruiz
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California 90095-1569, United States
| | - Alexander F Simafranca
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California 90095-1569, United States
| | - Nesibe Akmanşen-Kalayci
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California 90095-1569, United States
| | - Eric C Wu
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California 90095-1569, United States
| | - Evan Doud
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California 90095-1569, United States
| | - Zerina Mehmedović
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California 90095-1569, United States
| | | | - Minh D Phan
- Center for Neutron Science, Department of Chemical and Biochemical Engineering, University of Delaware, Newark, Delaware 19716, United States
| | - Alexander M Spokoyny
- 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
| | - Sarah H Tolbert
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California 90095-1569, United States
- Department of Materials Science and Engineering, University of California Los Angeles, Los Angeles, California 90095-1595, United States
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Verma A, Jackson NE. Assessing molecular doping efficiency in organic semiconductors with reactive Monte Carlo. J Chem Phys 2024; 160:104106. [PMID: 38465678 DOI: 10.1063/5.0197816] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2024] [Accepted: 02/22/2024] [Indexed: 03/12/2024] Open
Abstract
The addition of molecular dopants into organic semiconductors (OSCs) is a ubiquitous augmentation strategy to enhance the electrical conductivity of OSCs. Although the importance of optimizing OSC-dopant interactions is well-recognized, chemically generalizable structure-function relationships are difficult to extract due to the sensitivity and dependence of doping efficiency on chemistry, processing conditions, and morphology. Computational modeling for an integrated OSC-dopant design is an attractive approach to systematically isolate fundamental relationships, but requires the challenging simultaneous treatment of molecular reactivity and morphology evolution. We present the first computational study to couple molecular reactivity with morphology evolution in a molecularly doped OSC. Reactive Monte Carlo is employed to examine the evolution of OSC-dopant morphologies and doping efficiency with respect to dielectric, the thermodynamic driving for the doping reaction, and dopant aggregation. We observe that for well-mixed systems with experimentally relevant dielectric constants, doping efficiency is near unity with a very weak dependence on the ionization potential and electron affinity of OSC and dopant, respectively. At experimental dielectric constants, reaction-induced aggregation is observed, corresponding to the well-known insolubility of solution-doped materials. Simulations are qualitatively consistent with a number of experimental studies showing a decrease of doping efficiency with increasing dopant concentration. Finally, we observe that the aggregation of dopants lowers doping efficiency and thus presents a rational design strategy for maximizing doping efficiency in molecularly doped OSCs. This work represents an important first step toward the systematic integration of molecular reactivity and morphology evolution into the characterization of multi-scale structure-function relationships in molecularly doped OSCs.
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Affiliation(s)
- Archana Verma
- Department of Chemical and Biomolecular Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Nicholas E Jackson
- Department of Chemistry, University of Illinois Urbana-Champaign, Urbana, Illinois 61801, USA
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Xu C, Wang D. Theoretical Perspective of Enhancing Order in n-Doped Thermoelectric Polymers through Side Chain Engineering: The Interplay of Counterion-Backbone Interaction and Side Chain Steric Hindrance. NANO LETTERS 2024; 24:1776-1783. [PMID: 38284760 DOI: 10.1021/acs.nanolett.3c04829] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2024]
Abstract
Donor-acceptor (D-A) copolymers doped with n-type dopants are widely sought after for their potential in organic thermoelectric devices. However, the existing structural disorder significantly hampers their charge transport and thermoelectric performance. In this Letter, we propose a mechanism to mitigate this disorder through side chain engineering. Utilizing molecular dynamics simulations, we demonstrate that strong Coulomb interactions between counterions and charged polymer backbones induce a transition in the stacking arrangement of the polymer backbones from a slipped to a vertical configuration. However, the presence of side chain steric hindrance impedes the formation of closely packed and ordered vertical stacking arrangements, resulting in greater distances between adjacent backbones and a higher level of structural disorder in the doped films. Therefore, we propose minimizing side chain steric hindrance to enhance the structural order in doped films. Our findings provide essential insights for advancing high-performance thermoelectric polymers.
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Affiliation(s)
- Chunlin Xu
- Laboratory of Flexible Electronics Technology, Tsinghua University, Beijing 100084, People's Republic of China
- MOE Key Laboratory of Organic OptoElectronics and Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing 100084, People's Republic of China
| | - Dong Wang
- Laboratory of Flexible Electronics Technology, Tsinghua University, Beijing 100084, People's Republic of China
- MOE Key Laboratory of Organic OptoElectronics and Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing 100084, People's Republic of China
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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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Bhat V, Callaway CP, Risko C. Computational Approaches for Organic Semiconductors: From Chemical and Physical Understanding to Predicting New Materials. Chem Rev 2023. [PMID: 37141497 DOI: 10.1021/acs.chemrev.2c00704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
While a complete understanding of organic semiconductor (OSC) design principles remains elusive, computational methods─ranging from techniques based in classical and quantum mechanics to more recent data-enabled models─can complement experimental observations and provide deep physicochemical insights into OSC structure-processing-property relationships, offering new capabilities for in silico OSC discovery and design. In this Review, we trace the evolution of these computational methods and their application to OSCs, beginning with early quantum-chemical methods to investigate resonance in benzene and building to recent machine-learning (ML) techniques and their application to ever more sophisticated OSC scientific and engineering challenges. Along the way, we highlight the limitations of the methods and how sophisticated physical and mathematical frameworks have been created to overcome those limitations. We illustrate applications of these methods to a range of specific challenges in OSCs derived from π-conjugated polymers and molecules, including predicting charge-carrier transport, modeling chain conformations and bulk morphology, estimating thermomechanical properties, and describing phonons and thermal transport, to name a few. Through these examples, we demonstrate how advances in computational methods accelerate the deployment of OSCsin wide-ranging technologies, such as organic photovoltaics (OPVs), organic light-emitting diodes (OLEDs), organic thermoelectrics, organic batteries, and organic (bio)sensors. We conclude by providing an outlook for the future development of computational techniques to discover and assess the properties of high-performing OSCs with greater accuracy.
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Affiliation(s)
- Vinayak Bhat
- Department of Chemistry & Center for Applied Energy Research, University of Kentucky, Lexington, Kentucky 40506-0055, United States
| | - Connor P Callaway
- Department of Chemistry & Center for Applied Energy Research, University of Kentucky, Lexington, Kentucky 40506-0055, United States
| | - Chad Risko
- Department of Chemistry & Center for Applied Energy Research, University of Kentucky, Lexington, Kentucky 40506-0055, United States
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Control Aggregation of P3HT in Solution for High Efficiency Doping: Ensuring Structural Order and the Distribution of Dopants. CHINESE JOURNAL OF POLYMER SCIENCE 2023. [DOI: 10.1007/s10118-023-2939-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/09/2023]
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