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초록

We report optoelectronic synaptic behaviors of WO3-based devices with symmetric (Ag/WO3/Ag) and asymmetric (Ag/WO3/Pt) electrode configurations to emulate biological learning and memory functions. Structural and spectroscopic analyses confirm the presence of oxygen vacancies and deep-level defects, which contribute to persistent photoconductivity and defect-mediated emissions. Both devices exhibit light-induced excitatory postsynaptic current (EPSC) modulation depending on ultraviolet pulse duration, intensity, number, and frequency, mimicking synaptic potentiation. The Ag/WO3/Ag device shows consistently higher EPSC, faster learning, and longer retention than its asymmetric counterpart due to improved carrier injection and reduced interfacial barriers. Learning–forgetting experiments reveal that repeated optical stimulation enables faster learning and enhanced memory retention in both structures. Visual memory mapping using 3 × 3 pixel arrays further demonstrate spatial encoding and gradual forgetting of a “T”-shaped pattern, with the symmetric device retaining higher contrast over time. These findings highlight the critical role of electrode structure in tuning optoelectronic synaptic performance and suggest that defect-engineered WO3 thin films with optimized interfaces are promising candidates for neuromorphic vision and light-driven memory applications.

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