Flexible Optical Synapses Based on In 2 Se 3 /MoS 2 Heterojunctions for Artificial Vision Systems in the Near-Infrared Range.

Near-infrared (NIR) synaptic devices integrate NIR optical sensitivity and synaptic plasticity, emulating the basic biomimetic function of the human visual system and showing great potential in NIR artificial vision systems. However, the lack of semiconductor materials with appropriate band gaps for NIR photodetection and effective strategies for fabricating devices with synaptic behaviors limit the further development of NIR synaptic devices. Here, a two-terminal NIR synaptic device consisting of the In 2 Se 3 /MoS 2 heterojunction has been constructed, and it exhibits fundamental synaptic functions. The reduced band gap and potential barrier of In 2 Se 3 /MoS 2 heterojunctions are essential for NIR synaptic plasticity. In addition, the NIR synaptic properties of In 2 Se 3 /MoS 2 heterojunctions under strain have been studied systematically. The ΔEPSC of the In 2 Se 3 /MoS 2 synaptic device can be improved from 38.4% under no strain to 49.0% under a 0.54% strain with a 1060 nm illumination for 1 s at 100 mV. Furthermore, the artificial NIR vision system consisting of a 10 × 10 In 2 Se 3 /MoS 2 device array has been fabricated, exhibiting image sensing, learning, and storage functions under NIR illumination. This research provides new ideas for the design of flexible NIR synaptic devices based on 2D materials and presents many opportunities in artificial intelligence and NIR vision systems.