Carrier–Carrier Repulsion Limits the Conductivity of N-Doped Organic Semiconductors

Xuwen Yang, Gang Ye, Jian Liu, Ryan C. Chiechi, L. Jan Anton Koster*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

4 Citations (Scopus)
75 Downloads (Pure)

Abstract

Molecular doping is a key strategy to enhance the electrical conductivity of organic semiconductors. Typically, the electrical conductivity shows a maximum value upon increased doping, after which the conductivity decreases. This decrease in conductivity is commonly attributed to unfavorable changes in the morphology. However, in recent simulation work, has shown, that the conductivity—at high doping—is instead limited by electron–electron repulsion rather than by morphology, at least for some material combinations. Based on the simulations, this limitation is expected to show up in the dependence of the Seebeck coefficient versus carrier density: the Seebeck coefficient will follow Heike's formula if carrier–carrier repulsion limits the conductivity. Here, the electrical conductivity and Seebeck coefficient are measured as a function of doping for a series of n-type organic semiconductors. Additionally, the resulting carrier density is measured using metal-insulator-semiconductor diodes, which link dopant loading and the number of charge carriers. At high carrier densities, the Seebeck coefficient indeed follows Heike's formula, confirming that the conductivity is limited by carrier–carrier repulsion rather than by morphological effects. This study shows that current models of hopping transport in organic semiconductors may be incomplete. As a result, this study offers novel insights in the design of organic semiconductors.

Original languageEnglish
Article number2404397
Number of pages7
JournalAdvanced materials
Volume36
Issue number44
DOIs
Publication statusPublished - 1-Nov-2024

Keywords

  • doping
  • electrical conductivity
  • hopping transport
  • organic semiconductors

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