ION MODULATED ORGANIC TRANSISTORS - Doria

Nikolai Kaihovirtaa) b)3. RESULTS AND DISCUSSIONS10-5V D =-1.5V1st sweep1st sweep25th10 -610 -6I D/ A10 -725thV D=-0.4V10 -7I D/ A10 -8-2 -1 0 1V G/V-1.5 -1.0 -0.5 0.0 0.5V G/VFigure 3.17. 25 consecutive forward scans for PTFE:PFSA-based MemFETsmeasured (a) in the saturated region, and (b) in the linear region.Moreover, in Figure 3.17 (b), the electric potential never exceeds 1.2 Vbetween any two electrodes. Based on the results it can be concluded thatthe onset for the degradation of the transfer-curve, in Figure 3.17 (a), isbias-dependent. These results correspond with the aforementionedobservations in Figures 3.15 and 3.16.SC 6 H 13-e - +H 2O+e - S +S+ e - + 2H + DiketonesSulfonesC 6 H 13C 6 H 13OCarboxylic acidsScheme 3.1. The obtained results in Section 3.4.2 support the following reactionmechanism. Reversible doping of the P3HT occurs at -1.2 V < V G < 0 V for thePTFE:PFSA-based MemFET. At V G < -1.2 V, oxidative degradation of theP3HT will be initiated by significant water electrolysis in the hydrouselectrolyte. The sulfoxide group will further react and the semiconductingproperties of the P3HT will be lost.The experimental results obtained in this work point towards thedegradation of polythiophenes by oxidation, which is initiated by waterelectrolysis in the hydrous electrolyte (Scheme 3.1). For the PTFE:PFSAbasedMemFET the onset for severe oxidative degradation is at V G ≈ -1.2V. (Over)oxidative degradation of polythiophene-derivatives has beenstudied before [71, 72, 77-79]. For example, according to Barsch, et. al.[71], the complete degradation mechanism consists of several steps that40