Simulazioni al computer e analisi sperimentale di materiali per il dispositivo organico memristive

Abstract

This thesis reports the results obtained during three years of PhD program in a co-tutorship agreement between Parma University (under the supervision of Prof. Victor Erokhin and cosupervision of Dr. Silvia Battistoni) and Kazan Federal University (under the supervision of Prof. Dmitrii Tayurskii). This research is focused on a combined theoretical and experimental study of materials for the organic memristive devices, namely, solid polyelectrolyte optimization towards design the device with improved characteristics starting from the optimization of materials and their properties. Poly(ethylene oxide)(PEO)-based solid polyelectrolyte is a medium providing reversible redox reactions in the acrive zone of the organic memristive device, composed of the thin polyaniline (PANI) film. Ionic transport in the solid polyelectrolyte media is a key characteristic responsible for the improved response speed ot the device. Polyelectrolyte structure mostly defines ionic movements, thus it should be constant over time and from sample to sample to provide endurance and reproducibility of the organic memristive device.

Initially, the study was addressed to probing the lithium transport in PEO using pulsed gradient field nuclear magnetic resonance technique. Then, using molecular dynamics simulations with a simple amorphous polyelectrolyte model we have investigated polyelectrolyte structure and lithium transport, revealing water content effect on these properties. X-ray diffractometry was used to examine polyelectrolyte composition of real systems and confirmed the results of the simulations. Further, electrochemical characterization of the polyelectrolyte/electrode and polyelectrolyte/PANI-coated electrode was done.

Taking into account the results of the complex theoretical and experimental studies, the organic memristive device, fabricated using the polyelectrolyte, containing half of the standard lithium salt concentration, was characterized. The improvement of its kinetic properties was explained in terms of the underlying ionic transport.