Multifunctional Electronics Enabled by Ion-Based Organic Electrochemical Transistor with Large Threshold Voltage Tunability Window

Organic electrochemical transistors (OECTs) have emerged as versatile tools in areas such as bioelectronics, wearable devices, and neuromorphic computing. Their advantages include excellent transconductance, low power requirements, and adaptability to different substrates, making them ideal for diverse applications. The control of threshold voltage (<i>V</i>_th) is important for reducing power consumption and enhancing noise margin in complementary circuits. Furthermore, a wide range of <i>V</i>_th tuning can induce transitions between the depletion mode and accumulation mode, which is particularly helpful for generating spiking and nonlinear dynamics for building artificial spiking neurons. However, only a small category of conjugated polymers can be cycled stably and reversibly between a highly doped state and a dedoped state in aqueous electrolytes. Here, we demonstrate the use of different anions to induce threshold voltage shift from -0.16 V to +0.29 V, while maintaining high transconductance (>7 mS), high ON/OFF ratio (>10⁵) and negligible current degradation for over 10,000 cycles. The dynamic tunability in <i>V</i>_th allows a single OECT to have different operating modes and voltage windows, enabling multifunctional devices. We successfully demonstrate a zero-gate biased voltage amplifier for high-performing electrophysiological signal recording (electrocardiography, electromyography, and electrooculography), complementary inverters with high gain and full rail-to-rail swing, as well as organic artificial spiking neurons that display S-shaped negative differential resistance with oscillation functionality and mimicking human neurobiological functions via integration with tactile and photosensors. Our approach offers a straightforward method to tailor OECTs via anion selection, advancing low-power bioelectronics and neuromorphic systems.