Vertical organic electrochemical transistors: recent developments and applications

Abstract

Since their advent in 1984, Organic Electrochemical Transistors (OECT) have emerged as a versatile platform for biosensing, logic circuitry, and neuromorphic computing, thanks to their unique combination of low-voltage operation, high transconductance, biocompatibility and ion-to-electron transduction capabilities. In the 2010s, a design change characterized by the vertical stacking of the source and drain electrodes resulted in the vertical OECT (vOECT). This new architecture allowed a reduction of device footprint while increasing its transconductance (gm) and operational speed, thus improving performance and enabling further miniaturization. Here, I present a case where the vertical architecture promotes enhanced performance for p-type accumulation mode OECTs, resulting in one of best ratios of gm by footprint area. Next, design of vOECT complementary inverters is discussed, achieving large gains (≈200 V/V), switching times of 1ms and stability around 18000 cycles. Finally, non-volatile memories based on vOECTs are presented as promising candidates for neuromorphic computing building blocks. In these devices, the memory level transition is associated with the physical deposition or removal of a fiber-like channel within cavities between the source and drain electrodes via electropolymerization.