Tunable anti-ambipolar vertical bilayer organic electrochemical transistor enable neuromorphic retinal pathway
Anti-ambipolar transistors feature a drain current that moves from OFF to ON to OFF states with increasing gate bias. This property is intrinsic to some conjugated polymers. However, limited stable and tunable anti-ambipolar organic materials prevent the design of integrated, tunable, and multifunctional neuromorphic and logic-based systems. We offer a general approach for tuning anti-ambipolar characteristics through the design of a novel vertical OECT (vOECT) based on a p-n bilayer. This architecture allows reduction of device footprint and, by controlling the bilayer materials, tuning of the anti-ambipolarity characteristics. Our bilayer vertical architecture enables control of the device’s on and off threshold voltages, and peak position, by property selecting materials and thickness ratios. These anti-ambipolar bilayer vOECTs enable tunable threshold spiking neurons and logic gates, for bio-interfacing applications. To bring these concepts together, we used the logic gates to replicate the graded potentials processing of horizontal cells, while the tunable spiking circuits served to perform the spike encoding functions of retinal ganglion cells. This mimics the retinal pathway encoding wavelength and light intensity information, heralding future opportunities for customized and multifunctional neuromorphic circuitry.
