Largest‐Dynamic‐Range and 10 ⁶ ‐Rectification‐Ratio Optoelectronic Synapses Based on Type‐I I‐2D/3D Heterojunction With Optically‐Stimulated Bidirectional Synaptic Functions

ABSTRACT The emerging vertically two‐terminal optoelectronic synaptic devices have attracted significant attention due to their structural and performance advantages. However, most existing devices are limited to optically unidirectional modulation and suffer from restricted synaptic weight ranges and poor rectification characteristics, hindering their integration into neuromorphic systems. Here, a novel type‐I two‐terminal optoelectronic synaptic architecture based on an iodinated two‐dimensional/three‐dimensional (I‐2D/3D) perovskite heterostructure is proposed. The devices demonstrate electrical‐assisted monochromatic optically stimulated bidirectional synaptic behavior, enabled by ion migration, carrier trapping, and recombination effects. The incorporation of the I‐2D perovskite layer yields an exceptional rectification ratio of 1 × 10 ⁶ and significantly enhances the synaptic weight range to 34.4, outperforming previously reported perovskite‐based counterparts. Bidirectional synaptic functions and their excellent performance metrics arise from the unique design of type‐I I‐2D/3D heterojunction that improves the carrier separation capability to an optimal balance state. Furthermore, the YOLOv8 model, constructed based on synaptic devices, achieves accuracy comparable to pure software models when recognizing the VOC2012 dataset and demonstrates real‐time moving object detection in video streams, with average accuracies of 91%, 90%, and 89% for bicycles, persons, and cars, respectively. This work presents a novel strategy for bidirectional optoelectronic synapses, advancing their application in neuromorphic dynamic visual systems.