Device Physics and Switching Speed in Polymer-Based Artificial Synapses: Towards “Iontronics”

Polymer-based artificial synapses have shown outstanding performance in terms of switching speed, switching energy and endurance. Indeed, devices that can switch with 20 ns pulses and can undergo a read-write cycle in under 1 µs have been demonstrated. Furthermore, we have shown that they can be switched billions of times with no degradation. These are very unusual featured for organic semiconductors, which are usually plagues with slow speeds and weak reliability. In order to understand the origins of this performance we have developed a suite of operando characterization techniques that allow to study the materials structural evolution during biasing. We show that the highest performance devices are permeated with electrolyte in the form of neutral pairs, essentially acting as internally-gated transistors. Furthermore, we show that despite intercalating and expelling large ions, switching occurs with minimal structural disruption. These features may enable the operation of a broader category of “iontronic” devices that rely on ionic motion yet achieve high speeds compatible with electronics.