<i>I</i>-<i>V</i> characteristics and voltage dependence of pH-sensitive organic electrochemical transistors

Abstract

The pH-sensitive organic electrochemical transistors are expected to be widely used in wearable electronic devices for in-situ physiological monitoring. However, the unclear current-voltage relationship seriously hinders its development in design, optimization, and application. In the current work, the current-voltage characteristic of pH-sensitive organic electrochemical transistors is constructed by combining the electrochemical equilibrium equation with the series model of differential capacitances formed at gate electrode/electrolyte and semiconductor channel/electrolyte interface. Moreover, a pH-sensitive organic electrochemical transistor is constructed by using poly (3,4- ethylenedioxythiophene)/polystyrene sulfonate as the semiconductor layer material and modifying the gate electrode with pH-sensitive polymer (poly (3,4-ethylenedioxythiophene)/bromothymol blue). The effectiveness of the theoretical model is verified by investigating the output, transfer, and pH response characteristics of the pH-sensitive organic electrochemical transistor. The experimental results show that the detection sensitivity could be up to 0.22 mA·pH·unit&lt;sup&gt;-1&lt;/sup&gt;, and the pH response is gate-bias dependent. Then, a polynomial indicating the gate bias effect is introduced to modify the current-voltage characteristic equation. The goodness of fitting the theoretical model to the experimental results of transfer curves is found to be 0.998. The comparison of experimental and theoretical results of the gate bias corresponding to the peak transconductance and pH sensitivity responding to gate bias could also verify the effectiveness of the modified theoretical model. The results could provide theoretical support for the design and manufacture of pH-sensitive organic electrochemical transistors bases flexible biosensors.

Pulse electrochemical synaptic transistor for supersensitive and ultrafast biosensors

“…The linear range is mainly determined by the physicochemical properties of PEDOT:BTB, which could be verified through cyclic voltammetry experiments (Figure S1-7) and is consistent with other reports. 16,39,44,45 Furthermore, the sensitivity is also expressed by the gate bias offset (ΔV G,offset ) for further comparisons of the optimal voltage point (as shown in the bottom panel of Figure 3K), in which the ΔV G,offset is defined as the difference between the equivalent gate bias (V G equ ) and the actual gate bias (0 V), where V G equ signifies the gate bias assuming that there is almost no effect of H + but necessary to obtain the same sourcedrain current. Herein, the i DS obtained at pH = 8 is used for calibrating.…”