Redox tunable conjugated radicals enable low threshold voltage memristors for artificial synapses

Organic molecules with reversible redox are emerging as promising materials for low power memristors. However, the structure-property relationship between the molecular structure and threshold voltage is not clear; achieving low threshold voltage memristors is still a challenge. To address this issue, a series of conjugated Blatter radicals with tunable redox were designed and synthesized by varying the functional groups. It was found that the positive redox potentials of these radicals decrease with an increase in the electron donating strength of functional groups, leading to a corresponding reduction in the threshold voltages of the fabricated memristors. Notably, methoxy and dimethylamine substituted radicals achieve low threshold voltages of 0.51 and 0.48 V, respectively, with power consumption as low as 2.04 and 6.24 nJ. Mechanistic studies confirm that resistive switching arises from the reversible radical redox transitions. The applications of these memristors in synaptic plasticity, photoimaging and image recognition are demonstrated. This work presents a promising strategy for developing low threshold voltage memristive materials.