Intrinsic Defect-Driven Synergistic Synaptic Heterostructures for Gate-Free Neuromorphic Phototransistors.

The optoelectronic synaptic devices based on two-dimensional (2D) materials offers great advances for future neuromorphic visual systems with dramatically improved integration density and power efficiency. The effective charge capture and retention have been considered as one vital prerequisite to realize the synaptic memory function. However, the current 2D synaptic devices are predominantly relied on materials with artificially-engineered defects or intricate gate-controlled architectures to realize the charge trapping process. These approaches, unfortunately, suffer from the degradation of pristine materials, rapid device failure, and unnecessary complication of device structures. To address these challenges, we herein introduce an innovative gate-free heterostructure paradigm. The heterostructure presents a distinctive dome-like morphology wherein a defect-rich Fe 7 S 8 core is enveloped snugly by a curved MoS 2 dome shell (Fe 7 S 8 @MoS 2 ), allowing the realization of effective photocarrier trapping through the intrinsic defects in the adjacent Fe 7 S 8 core. The resultant neuromorphic devices exhibit remarkable light-tunable synaptic behaviors with memory time up to ∼800 s under single optical pulse, thus demonstrating great advances in simulating visual recognition system with significantly improved image recognition efficiency. The emergence of such heterostructures foreshadows a promising trajectory for underpinning future synaptic devices, catalyzing the realization of high-efficiency and intricate visual processing applications. This article is protected by copyright. All rights reserved.