Influence of dopant size and electron affinity on the electrical conductivity and thermoelectric properties of a series of conjugated polymers

Zhiming Liang, Yadong Zhang, Maryam Souri, Xuyi Luo, Alex M. Boehm, Ruipeng Li, Yan Zhang, Tairan Wang, Doo Young Kim, Jianguo Mei, Seth R. Marder, Kenneth R. Graham

Research output: Contribution to journalArticlepeer-review

116 Scopus citations

Abstract

Chemical doping is widely used to manipulate the electrical and thermoelectric properties of organic semiconductors, yet intelligent design of polymer-dopant systems remains elusive. It is challenging to predict the electrical and thermoelectric properties of doped organic semiconductors due to the large number of variables impacting these properties, including film morphology, dopant and polymer energetics, dopant size, and degree of polaron delocalization. Herein, a series of dopants with varying sizes and electron affinities (EAs) are combined with polymers of differing ionization energies (IEs) to investigate how the difference between polymer IE and dopant EA influences the doping efficiency and electrical conductivity, and how the dopant size influences the thermoelectric properties. Our experiments demonstrate that at low doping levels the doping efficiency strongly depends on the difference between the polymer IE and dopant EA; the effectiveness of doping on increasing electrical conductivity drastically decreases at high loadings for the molybdenum dithiolene complexes, while FeCl3 remains effective at high loadings; and the large molybdenum complexes lead to more delocalized polarons as compared to FeCl3. To take advantage of the complementary doping characteristics of the molybdenum complexes and FeCl3, both dopants are employed simultaneously to reach high power factors at relatively low dopant concentrations.

Original languageEnglish
Pages (from-to)16495-16505
Number of pages11
JournalJournal of Materials Chemistry A
Volume6
Issue number34
DOIs
StatePublished - 2018

Bibliographical note

Publisher Copyright:
© 2018 The Royal Society of Chemistry.

ASJC Scopus subject areas

  • General Chemistry
  • Renewable Energy, Sustainability and the Environment
  • General Materials Science

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