Hysteresis and Gate Bias Stress Effects in Organic Electrochemical Transistors based on Room Temperature Ionic Liquids*

Organic Electrochemical Transistors (OECTs) transduce ionic into electronic signals. The transconductance of OECTs is in the mS range and outperforms other traditional and emerging transistors.[1] Here, we show that the transconductance of OECTs is limited by a voltage dependent contact resistance at the source/drain electrodes.[2] By an optimization of the device geometry and by using a mixture of room temperature ionic liquid (C2MIM EtSo4) and PBS as an electrolyte, we reach a transconductance greater than 2 mS. For later applications of OECTs, the stability of these devices is of utmost importance. We investigate the origin of a hysteresis observed in the transfer characteristic and the origin of gate bias stress effects. We propose that these instabilities are caused by ions moving slowly inside the electrolyte and the semiconductor, leading to a different time constant and hence reversible gate stress bias effects. We discuss several approaches to minimize these instabilities.[3]

References

[1] D. Khodagholy, T. Doublet, P. Quilichini et al., Nat. Commun. 2013, 4, 1575.
[2] V. Kaphle, S. Liu, A. Al-Shadeedi, C.-M. Keum and B. Lüssem, Adv. Mater. 2016, 28, 8766.
[3] V. Kaphle, S. Liu, C-M Keum, B. Lüssem, Phys. Solidi Status 2018, doi.10.1002/pssa.20180063.