Highly Conducting Polythiophene Thin Films with Less Ordered Microstructure Displaying Excellent Thermoelectric Performance

Jiajia Zhang; Guangjie Song; Lin Qiu; Yanhui Feng; Jie Chen; Jie Yan; Liyao Liu; Xing Huang; Yutao Cui; Yimeng Sun; Wei Xu; Daoben Zhu

doi:10.1002/marc.201800283

Highly Conducting Polythiophene Thin Films with Less Ordered Microstructure Displaying Excellent Thermoelectric Performance

Macromol Rapid Commun. 2018 Jul 5:e1800283. doi: 10.1002/marc.201800283. Online ahead of print.

Authors

Jiajia Zhang^{1

2}, Guangjie Song³, Lin Qiu⁴, Yanhui Feng⁴, Jie Chen^{1

2}, Jie Yan^{1

2}, Liyao Liu^{1

2}, Xing Huang^{1

2}, Yutao Cui^{1

2}, Yimeng Sun^{1

2}, Wei Xu^{1

2}, Daoben Zhu^{1

2}

Affiliations

¹ Beijing National Laboratory for Molecular Sciences, Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China.
² School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China.
³ Beijing National Laboratory for Molecular Sciences, Key Laboratory of Engineering Plastics, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China.
⁴ School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing, 100083, China.

PMID: 29975438
DOI: 10.1002/marc.201800283

Abstract

Polythiophene (PTh) with highly regular molecular structure is synthesized as nearly amorphous thin films by electrochemical methods in a BFEE/DTBP mixed medium (BFEE = boron fluoride ethyl ether; DTBP = 2,6-di-tert-butypyridine). The doping level and film morphology of PTh are modulated through adjusting the current density applied during the polymerization process. A combined analysis with solid-state NMR, FT-IR, and Raman spectra reveals the molecular structural regularity of the resulted PTh films, which leads to the highest electrical conductivity up to 700 S cm^-1 for films obtained under an optimized current density of 1 mA cm^-2 . By applying the self-heating 3ω-method, thermal conductivities are measured along the in-plane direction. A highly reduced Lorenz number of 6.49 × 10^-9 W Ω K^-2 and low lattice thermal conductivity of 0.21 W m^-1 K^-1 were extracted based on the analyses of the electrical and thermal conductivities according to the Wiedemann-Franz Law; the former is about one-third of the Sommerfeld value. Finally, the maximized ZT value can reach up to 0.10 under room temperature, which shows that the highly conducting polymers with less ordered structure is the practical direction for developing organic thermoelectric materials.

Keywords: conducting polymers; electrochemical polymerization; polythiophene; thermal conductivity; thermoelectric materials.