Unravelling Disorder Effects on Thermoelectric Properties of Semicrystalline Polymers in a Wide Range of Doping Levels

Woojin Choi; Soohyun Kim; Soonyong Lee; Changhwa Jung; Ayushi Tripathi; Yoonjoo Lee; Han Young Woo; Hyunjung Lee

doi:10.1002/smtd.202201145

Unravelling Disorder Effects on Thermoelectric Properties of Semicrystalline Polymers in a Wide Range of Doping Levels

Woojin Choi, Soohyun Kim, Soonyong Lee, Changhwa Jung, Ayushi Tripathi, Yoonjoo Lee, Han Young Woo, Hyunjung Lee

Department of Chemistry

Research output: Contribution to journal › Article › peer-review

1 Citation (Scopus)

Abstract

Thermoelectric (TE) performance of a specific semicrystalline polymer is studied experimentally only in a limited range of doping levels with molecular doping methods. The doping level is finely controlled via in situ electrochemical doping in a wide range of carrier concentrations with an electrolyte ([PMIM]⁺[TFSI]⁻)-gated organic electrochemical transistor system. Then, the charge generation/transport and TE properties of four p-type semicrystalline polymers are analyzed and their dynamic changes of crystalline morphologies and local density of states (DOS) during electrochemical doping are compared. These polymers are synthesized based on poly[(2,5-bis(2-alkyloxy)phenylene)-alt-(5,6-difluoro-4,7-di(thiophene-2-yl)benzo[c][1,2,5]thiadiazole)] by varying side chains: With oligoethylene glycol (OEG) substituents, facile p-doping is achieved because of easy penetration of TFSI⁻ ions into the polymer matrix. However, the charge transport is hindered with longer OEG chains length because of the enhanced insulation. Therefore, with the shortest OEG substituents the electrical conductivity (30.1 S cm⁻¹) and power factor (2.88 µW m⁻¹ K⁻²) are optimized. It is observed that all polymers exhibit p- to n-type transition in Seebeck coefficients in heavily doped states, which can be achieved by electrochemical doping. These TE behaviors are interpreted based on the relation between the localized DOS band structure and molecular packing structure during electrochemical doping.

Original language	English
Article number	2201145
Journal	Small Methods
Volume	7
Issue number	2
DOIs	https://doi.org/10.1002/smtd.202201145
Publication status	Published - 2023 Feb 17

Bibliographical note

Funding Information:
W.C., S.K., and S.L. contributed equally to this work. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (nos. 2021R1A2C2008325, 2021R1A4A1030944, 2019R1A2C2085290, and 2019R1A6A1A11044070). This work was also supported by the KU‐KIST School Program.

Funding Information:
W.C., S.K., and S.L. contributed equally to this work. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (nos. 2021R1A2C2008325, 2021R1A4A1030944, 2019R1A2C2085290, and 2019R1A6A1A11044070). This work was also supported by the KU-KIST School Program.

Publisher Copyright:
© 2022 Wiley-VCH GmbH.

Keywords

electrochemical doping
energy-dependent thermoelectric properties
heavily doped states
in situ investigations
localized density of states
semicrystalline polymers

ASJC Scopus subject areas

Chemistry(all)
Materials Science(all)

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10.1002/smtd.202201145

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title = "Unravelling Disorder Effects on Thermoelectric Properties of Semicrystalline Polymers in a Wide Range of Doping Levels",

abstract = "Thermoelectric (TE) performance of a specific semicrystalline polymer is studied experimentally only in a limited range of doping levels with molecular doping methods. The doping level is finely controlled via in situ electrochemical doping in a wide range of carrier concentrations with an electrolyte ([PMIM]+[TFSI]−)-gated organic electrochemical transistor system. Then, the charge generation/transport and TE properties of four p-type semicrystalline polymers are analyzed and their dynamic changes of crystalline morphologies and local density of states (DOS) during electrochemical doping are compared. These polymers are synthesized based on poly[(2,5-bis(2-alkyloxy)phenylene)-alt-(5,6-difluoro-4,7-di(thiophene-2-yl)benzo[c][1,2,5]thiadiazole)] by varying side chains: With oligoethylene glycol (OEG) substituents, facile p-doping is achieved because of easy penetration of TFSI− ions into the polymer matrix. However, the charge transport is hindered with longer OEG chains length because of the enhanced insulation. Therefore, with the shortest OEG substituents the electrical conductivity (30.1 S cm−1) and power factor (2.88 µW m−1 K−2) are optimized. It is observed that all polymers exhibit p- to n-type transition in Seebeck coefficients in heavily doped states, which can be achieved by electrochemical doping. These TE behaviors are interpreted based on the relation between the localized DOS band structure and molecular packing structure during electrochemical doping.",

keywords = "electrochemical doping, energy-dependent thermoelectric properties, heavily doped states, in situ investigations, localized density of states, semicrystalline polymers",

author = "Woojin Choi and Soohyun Kim and Soonyong Lee and Changhwa Jung and Ayushi Tripathi and Yoonjoo Lee and Woo, {Han Young} and Hyunjung Lee",

note = "Funding Information: W.C., S.K., and S.L. contributed equally to this work. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (nos. 2021R1A2C2008325, 2021R1A4A1030944, 2019R1A2C2085290, and 2019R1A6A1A11044070). This work was also supported by the KU‐KIST School Program. Funding Information: W.C., S.K., and S.L. contributed equally to this work. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (nos. 2021R1A2C2008325, 2021R1A4A1030944, 2019R1A2C2085290, and 2019R1A6A1A11044070). This work was also supported by the KU-KIST School Program. Publisher Copyright: {\textcopyright} 2022 Wiley-VCH GmbH.",

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AU - Jung, Changhwa

AU - Tripathi, Ayushi

AU - Lee, Yoonjoo

AU - Woo, Han Young

AU - Lee, Hyunjung

N1 - Funding Information: W.C., S.K., and S.L. contributed equally to this work. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (nos. 2021R1A2C2008325, 2021R1A4A1030944, 2019R1A2C2085290, and 2019R1A6A1A11044070). This work was also supported by the KU‐KIST School Program. Funding Information: W.C., S.K., and S.L. contributed equally to this work. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (nos. 2021R1A2C2008325, 2021R1A4A1030944, 2019R1A2C2085290, and 2019R1A6A1A11044070). This work was also supported by the KU-KIST School Program. Publisher Copyright: © 2022 Wiley-VCH GmbH.

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N2 - Thermoelectric (TE) performance of a specific semicrystalline polymer is studied experimentally only in a limited range of doping levels with molecular doping methods. The doping level is finely controlled via in situ electrochemical doping in a wide range of carrier concentrations with an electrolyte ([PMIM]+[TFSI]−)-gated organic electrochemical transistor system. Then, the charge generation/transport and TE properties of four p-type semicrystalline polymers are analyzed and their dynamic changes of crystalline morphologies and local density of states (DOS) during electrochemical doping are compared. These polymers are synthesized based on poly[(2,5-bis(2-alkyloxy)phenylene)-alt-(5,6-difluoro-4,7-di(thiophene-2-yl)benzo[c][1,2,5]thiadiazole)] by varying side chains: With oligoethylene glycol (OEG) substituents, facile p-doping is achieved because of easy penetration of TFSI− ions into the polymer matrix. However, the charge transport is hindered with longer OEG chains length because of the enhanced insulation. Therefore, with the shortest OEG substituents the electrical conductivity (30.1 S cm−1) and power factor (2.88 µW m−1 K−2) are optimized. It is observed that all polymers exhibit p- to n-type transition in Seebeck coefficients in heavily doped states, which can be achieved by electrochemical doping. These TE behaviors are interpreted based on the relation between the localized DOS band structure and molecular packing structure during electrochemical doping.

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Unravelling Disorder Effects on Thermoelectric Properties of Semicrystalline Polymers in a Wide Range of Doping Levels

Abstract

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Keywords

ASJC Scopus subject areas

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