Impact of Molecular Weight on Molecular Doping Efficiency of Conjugated Polymers and Resulting Thermoelectric Performances

Sang Eun Yoon, Bomi Kim, So Yeon Chun, Sang Yeon Lee, Dohyeon Jeon, Minju Kim, Solin Lee, Bo Eun Seo, Kang Suh Choi, Felix Sunjoo Kim, Taekyeong Kim, Hyungtak Seo, Kyungwon Kwak, Jong H. Kim, Bong Soo Kim

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

The effect of molecular weight of a series of conjugated polymers (CPs) on the doping efficiency, electrical conductivity, and related thermoelectric properties of doped CPs is studied. Low (L), medium (M), and high (H) molecular weight batches of PDFD-T polymers, based on difluorobenzothiadiazole and dithienosilole moieties, are synthesized and denoted as PDFD-T(L), PDFD-T(M), and PDFD-T(H), respectively. Furthermore, to compare the effects of different donor moieties, donor units of PDFD-T(L) are structurally modified from thiophene to thienothiophene (TT) and dithienothiophene (DTT), denoted as PDFD-TT(L) and PDFD-DTT(L), respectively. After doping the CPs with FeCl3, d-PDFD-T(H) exhibits an electrical conductivity of 402.9 S cm−1, which is significantly higher than those of d-PDFD-T(L), d-PDFD-T(M), d-PDFD-TT(L), and d-PDFD-DTT(L). The highest power factor of 101.1 µW m−1 K−2 is achieved through organic thermoelectric devices fabricated using PDFD-T(H). Through various characterizations, it is demonstrated that CPs with a high molecular weight tend to have a high carrier mobility while maintaining their original crystallinity and good charge transport pathways even after doping. Therefore, it is suggested that optimizing the molecular weight of CPs is an essential strategy for maximal power generation from their doped CP films.

Original languageEnglish
Article number2202929
JournalAdvanced Functional Materials
Volume32
Issue number32
DOIs
Publication statusPublished - 2022 Aug 8

Keywords

  • conjugated polymers
  • electrical conductivity
  • molecular dopants
  • molecular weight
  • thermoelectric effect

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics

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