Conjugated-Backbone Effect of Organic Small Molecules for n-Type Thermoelectric Materials with ZT over 0.2

Dazhen Huang, Huiying Yao, Yutao Cui, Ye Zou, Fengjiao Zhang, Chao Wang, Hongguang Shen, Wenlong Jin, Jia Zhu, Ying Diao, Wei Xu, Chong An Di, Daoben Zhu

Research output: Contribution to journalArticlepeer-review

Abstract

Conjugated backbones play a fundamental role in determining the electronic properties of organic semiconductors. On the basis of two solution-processable dihydropyrrolo[3,4-c]pyrrole-1,4-diylidenebis(thieno[3,2-b]thiophene) derivatives with aromatic and quinoid structures, we have carried out a systematic study of the relationship between the conjugated-backbone structure and the thermoelectric properties. In particular, a combination of UV-vis-NIR spectra, photoemission spectroscopy, and doping optimization are utilized to probe the interplay between energy levels, chemical doping, and thermoelectric performance. We found that a moderate change in the conjugated backbone leads to varied doping mechanisms and contributes to dramatic changes in the thermoelectric performance. Notably, the chemically doped A-DCV-DPPTT, a small molecule with aromatic structure, exhibits an electrical conductivity of 5.3 S cm-1 and a high power factor (PF373 K) up to 236 μW m-1 K-2, which is 50 times higher than that of Q-DCM-DPPTT with a quinoid structure. More importantly, the low thermal conductivity enables A-DCV-DPPTT to possess a figure of merit (ZT) of 0.23 ± 0.03, which is the highest value reported to date for thermoelectric materials based on organic small molecules. These results demonstrate that the modulation of the conjugated backbone represents a powerful strategy for tuning the electronic structure and mobility of organic semiconductors toward a maximum thermoelectric performance.

Original languageEnglish (US)
Pages (from-to)13013-13023
Number of pages11
JournalJournal of the American Chemical Society
Volume139
Issue number37
DOIs
StatePublished - Sep 20 2017

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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