Anions Doping Induced Reversable Threshold Voltage Modulation for Organic Electrochemical Transistors

Controlling the threshold voltage in organic electrochemical transistors (OECTs) has been considered as a promising approach for customizing transistors to meet specific application requirements. By tuning the threshold voltage, OECTs can switch effectively in both accumulation mode and depletion mode, providing researchers with greater flexibility in circuit design. In this work, we propose anion doping induced threshold voltage modulation in OECTs for bioelectronics applications. By altering the doped anions (varying radius) in the aqueous liquid electrolyte, the threshold voltage of pgBTTT based OECTs can be shifted from -0.15 V (under 0.1 M NaCl) to 0.3 V (0.1 M NaTFSI). This wide range is sufficient for pgBTTT based OECTs to function as both accumulation and depletion mode transistors. To demonstrate their feasibility in various operating modes, we first employed pgBTTT-based OECTs doped with TFSI^- to construct a zero-gate biased ECG amplifier. This amplifier exhibited high amplification (23.3 μA), and the high transconductance at 0 V indicates that it requires only one power supply, significantly reducing power consumption. Next, we implemented a complementary logic circuit using the pgBTTT-based OECT doped with Cl^- as a pull-up transistor. The proposed complementary inverter exhibits high gain (59V/V) and a high noise margin with full rail-to-rail swing. Furthermore, we combined the features of both these two transistors (doped with Cl^- and TFSI^-) to create organic electrochemical nonlinear devices (OENDs). The exhibited S-shaped negative differential resistance (S-NDR) curve demonstrates oscillation functionality, similar to other spiking neurons but with a reduced transistor type, which is particularly useful for future multi-layer spiking neurons. In summary, the easily tunable threshold voltage of pgBTTT-based OECTs under different anions offers a simpler approach to customizing transistors for specific requirements, paving the way for further advancements in low-power bioelectronics.