New insight in the operation mechanism of Organic Memristive Devices: The role of PEO-based polyelectrolyte solute ions

Abstract The operation mechanism of polyaniline-based Organic Memristive Devices, synapse-like devices particularly important for neuromorphic applications, are further investigated to better clarify their principle of operation and in view of improving their performance, stability and reliability. In this framework, even though they have been studied extensively in the past, aspects of their operation mechanism require a better understanding. In earlier studies, an important role in terms of the promotion of device switching is attributed to lithium ions present in polyethylene oxide (PEO), which serves as the solid polyelectrolyte (SPE). In a recent work, the role of dopant ions as well as the material of the gate electrode have been assessed, suggesting that it is the chloride ions and silver, respectively, that are relevant for the system's memristive switching. The present paper further investigates the role of the solute ions in devices with various polyethylene oxide-based polyelectrolytes. In a series of experiments using a number of different polyelectrolyte dopant salts, we provide additional evidence that cations have no decisive effect on the memristive switching of the device, while the nature of the dopant anion, on the contrary, plays a crucial role. Moreover, giving an improved insight about the effects of the dopant in the SPE, this study shows that the polyelectrolyte is crucial for the performance of the device. To this end, it is shown that in addition to the hygroscopicity of the salt additive, it is quite important to consider also the lyotropicity of its ions to establish a favourable SPE structure. The results of our study provide a deeper understanding of the factors that cause the device's degradation and suggest novel approaches to improve stability, performance and endurance of the solid polyelectrolyte-based Organic Memristive Device.