OECT Device Physics

Organic electrochemical transistors (OECTs) are thin-film transistors with an organic semiconductor channel between source and drain electrodes. OECTs are structured much like organic field-effect transistors (OFETs) with the distinction that OECTs have an electrolyte layer between the channel and the gate electrode instead of a standard dielectric.  We develop and validate models that provide quantitative explanations for previously unexplained characteristics. Ultimately, these models inform the design of OECT sensors and circuits, and they provide a way to measure the material properties of the polymer semiconductors used in OECTs, thus aiding the development of new polymers for performance optimization in different applications.

The team

  • Megan Renny  (PhD Student)
  • Natalie Alvarado (Undergraduate Student)
  • Brenna Curvey (Undergraduate Student)

Learn more

  • J. T. Friedlein, J. Rivnay, D. H. Dunlap, I McCulloch, S. E. Shaheen, R. R. McLeod, George G. Malliaras, “,” Applied Physics Letters 111, 023301 (2017)
  • J. T. Friedlein, M. J. Donahue, S. E. Shaheen, G. G. Malliaras, and R. R. McLeod, “,” Advanced Materials 28, 8398–8404, 2016.
  • J. T. Friedlein, S. E. Shaheen, G. G. Malliaras, R. R. McLeod,  Advanced Electronic Materials 2015, pp. 1500189 (9 pages), 2015.
  • Jacob Friedlein,  Doctor of Philosophy in Electrical Engineering, ,  University of Colorado, 2017.

This work has been generously funded by

   

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Sample results

OECT

In an OECT, mobile ions are pushed from the electrolyte into the polymer semiconductor by a gate voltage. These ions dope (or de-dope) the semiconductor, changing its conductivity.  Unlike OFETs, ionic and electronic charge transport occurs throughout the volume of the condutive polymer channel.

OECT step response

Change in current through the channel (top) in response to a voltage step on the gain (bottom) compared to our model.  We extended the seminal work of Bernards and Malliaras, particularly by including the unusually high ionic displacement current.

OECT transconductance

The change in gate current in response to a change in gate voltage, called the transconductance, is very high in OECTs and exploited for high sensitivity.  We have explained the variation of transconductance with gate voltage by incorporating the impact of disorder in the semiconductor channel.