Tunable Linear Weight Modulation via Ion Dynamics in Electrolyte-Gated Synaptic Transistors: Molecular Dynamics and Experimental Insights into Ion Concentration Effects

H Lee and S Alosious and M Jin and Y Kim and T Luo and YS Kim, ADVANCED FUNCTIONAL MATERIALS (2025).

DOI: 10.1002/adfm.202517100

Electrolyte-gated transistors (EGTs) are promising candidates for low- power and energy-efficient artificial synapses utilizing rapid ion- mediated electrostatic and electrochemical reactions. However, the correlation between sub-nanosecond ion transport and linear conductance modulation remains elusive when analyzed solely by macroscopic electrical characterization. Here, molecular dynamics (MD) simulations are integrated with experiments using Li-EGTs at different ion concentrations. MD simulations quantify Li+ displacement, coordination environments, and ionic conductivity in poly(ethylene oxide) electrolytes, revealing suppressed Li+ diffusivity and reorganization of the ethylene oxide (EO) solvation structure at an EO:Li+ ratio of 8:1. EGTs are fabricated with different EO ratios to investigate the transition regime. Electrochemical impedance spectroscopy, optical microscopy, and X-ray diffraction confirm the MD-predicted ion dynamic transition at 8:1 EO ratio and identify phase crystallization at the ultrahigh 2:1 ratio. Consequently, Li-EGTs fabricated with the optimized 2:1 EO ratio successfully achieve an accuracy of 89.51% in neural network training. This study bridges atomic-scale insights and device performance, offering a systematic, precision-engineered framework for complex spatiotemporal ion dynamics in artificial synaptic EGTs.

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