A Van Der Waals Broadband Infrared Optical Synapse Enabling Orientation Detection.

A vision system with efficient infrared-sensitive optical synapses is crucial for enabling infrared radiation detection and target recognition for some predators hunting in the dark. Current 2D synaptic devices typically adopt the strategy of charge trap and release to achieve intelligent sensing and visual recognition. However, the response wavelength is limited in a narrow range (typically in visible) due to the intrinsic bandgap of these 2D materials. In this work, a broadband infrared optoelectronic synaptic device based on a few-layer graphene/CrOCl/few-layer graphene van der Waals (vdW) heterostructure is reported, featuring tunable spike timing-dependent plasticity and a broadband response range from the visible to the infrared (520-2000 nm). The broadband synaptic response in the tunneling device is attributed to the modulation of the tunneling barrier by strong interfacial coupling and charge transfer-induced long-wavelength charge order at the vdW interface. Integrated with reservoir computing technique, the tunneling device can efficiently detect images in different orientations, achieving a recognition accuracy exceeding 98%, and judge the possible escape directions of a mouse. This work not only allows us to explore broadband optical synapses by controlling the vdW interfacial coupling but also offers a promising solution for developing advanced infrared detection systems.