Charge Saturation and Intrinsic Doping in Electrolyte-Gated Organic Semiconductors

Timothy L. Atallah, Martin V. Gustafsson, Elliot Schmidt, C. Daniel Frisbie, X. Y. Zhu

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


Electrolyte gating enables low voltage operation of organic thin film transistors, but little is known about the nature of the electrolyte/organic interface. Here we apply charge-modulation Fourier transform infrared spectroscopy, in conjunction with electrical measurements, on a model electrolyte gated organic semiconductor interface: single crystal rubrene/ion-gel. We provide spectroscopic signature for free-hole like carriers in the organic semiconductor and unambiguously show the presence of a high density of intrinsic doping of the free holes upon formation of the rubrene/ion-gel interface, without gate bias (Vg = 0 V). We explain this intrinsic doping as resulting from a thermodynamic driving force for the stabilization of free holes in the organic semiconductor by anions in the ion-gel. Spectroscopy also reveals the saturation of free-hole like carrier density at the rubrene/ion-gel interface at Vg < -0.5 V, which is commensurate with the negative transconductance seen in transistor measurements.

Original languageEnglish (US)
Pages (from-to)4840-4844
Number of pages5
JournalJournal of Physical Chemistry Letters
Issue number23
StatePublished - Dec 3 2015


  • ion-gel
  • ionic gating
  • organic semiconductors
  • organic thin film transistor

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