Crossover from band-like to thermally activated charge transport in organic transistors due to strain-induced traps

Yaochuan Mei, Peter J. Diemer, Muhammad R. Niazi, Rawad K. Hallani, Karol Jarolimek, Cynthia S. Day, Chad Risko, John E. Anthony, Aram Amassian, Oana D. Jurchescu

Research output: Contribution to journalArticlepeer-review

61 Scopus citations

Abstract

The temperature dependence of the charge-carrier mobility provides essential insight into the charge transport mechanisms in organic semiconductors. Such knowledge imparts critical understanding of the electrical properties of these materials, leading to better design of high-performance materials for consumer applications. Here, we present experimental results that suggest that the inhomogeneous strain induced in organic semiconductor layers by the mismatch between the coefficients of thermal expansion (CTE) of the consecutive device layers of field-effect transistors generates trapping states that localize charge carriers. We observe a universal scaling between the activation energy of the transistors and the interfacial thermal expansion mismatch, in which band-like transport is observed for similar CTEs, and activated transport otherwise. Our results provide evidence that a high-quality semiconductor layer is necessary, but not sufficient, to obtain efficient charge-carrier transport in devices, and underline the importance of holistic device design to achieve the intrinsic performance limits of a given organic semiconductor. We go on to show that insertion of an ultrathin CTE buffer layer mitigates this problem and can help achieve band-like transport on a wide range of substrate platforms.

Original languageEnglish
Pages (from-to)E6739-E6748
JournalProceedings of the National Academy of Sciences of the United States of America
Volume114
Issue number33
DOIs
StatePublished - Aug 15 2017

Bibliographical note

Funding Information:
J.E.A. and C.R. thank the National Science Foundation (DMR-1627428) for support of calculations and organic semiconductor synthesis. The device work at Wake Forest was supported by the National Science Foundation under Grants ECCS-1254757 and DMR-1627925.

Publisher Copyright:
© 2017, National Academy of Sciences. All rights reserved.

Keywords

  • Charge-carrier mobility
  • Electronic traps
  • Organic devices
  • Organic field-effect transistors
  • Organic semiconductors

ASJC Scopus subject areas

  • General

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