Abstract The optically stimulated synaptic device incorporates gold nanoparticles (Au‐NPs) embedded within an atomic‐layer‐deposited HfTiO x /Al 2 O 3 bilayer, which enables the photonic modulation of synaptic plasticity. The HfTiO x /Au‐NP interface enhances visible light absorption and utilization efficiency by generating ionized oxygen vacancies through the neutral oxygen vacancy sites, thereby modulating the device conductance states. This architecture effectively mimics key biological synaptic functions, including paired‐pulse facilitation (PPF), memory transitions from short‐term to long‐term memory (STM to LTM), and spike‐rate‐dependent plasticity (SRDP). The device further demonstrates optical logic operations and Pavlovian associative learning under dual‐wavelength light stimulation (405 and 450 nm). The intensity‐dependent generation of photocarriers and their nonlinear interaction with oxygen vacancies enable robust synaptic behavior, facilitating the emulation of human visual perception in a 4 × 4 optoelectronic synapse array with short‐term memory capabilities. Moreover, the wavelength‐ and sequence‐dependent synaptic responses can be finely controlled for the design of light‐programmable reservoir computing systems. These results demonstrate the potential of the HfTiO x /Au‐NP/Al 2 O 3 switching layer as a promising platform for efficient neuromorphic computing and vision‐based information processing using integrated optoelectronic synapses.

Abstract Data processing through artificial synapses is gaining attention owing to the emergence of neuromorphic computing. Analog processing via these synapses can simultaneously handle large volumes of data; however, it is susceptible to interference from various environmental factors. Specifically, temperature changes can significantly affect overall signal characteristics, leading to substantial errors. Herein, an organic heterojunction‐based artificial synapse is presented that is capable of light–temperature antagonistic operations. The properly aligned band structure and trap sites, which are facilitated by oxygen penetration, enable the implementation of controlled synaptic characteristics, depending on temperature and light conditions. An increase in temperature resulted in a thermally enhanced synaptic current, while light irradiation reduced the synaptic current, with the reduction degree being dependent on the light intensity. Finally, a biomimetic analog processor system capable of signal stabilization under drastic temperature changes is implemented. The artificial synapse, which operates using a light–temperature antagonistic operation, can significantly expand the potential applications of artificial intelligence hardware.