Dual‐Functional Optoelectronic Devices Composed of Cs 3 Cu 2 I 5 /Graphene/Ge Multi‐Heterostructures Enabling Deep‐Ultraviolet Synaptic Behavior and Near‐Infrared Photodetection

ABSTRACT Multi‐functional optoelectronic devices that integrate the capacities of neuromorphic processing and photodetection are of pivotal importance for advancing optoelectronic techniques. Here, we present a dual‐functional optoelectronic device based on a multi‐heterostructure of Cs 3 Cu 2 I 5 /graphene/Ge, which realizes high‐performance deep‐ultraviolet (DUV) synaptic behavior and self‐driven near‐infrared (NIR) photodetection simultaneously. On one hand, the device leverages the photogating effect in the Cs 3 Cu 2 I 5 /graphene heterostructure to produce persistent photo‐conductivity, emulating synaptic behavior upon DUV light stimulation. Electron trapping by introducing B 4 PyMPM as capture sites significantly promotes spatial divorcement of photocarriers, guaranteeing remarkably improved synaptic characteristics. The utilizations in DUV fingerprint recognition with an accuracy of 97.8%, and optoelectronic reservoir computing with recognition accuracy reaching 100% for three 4‐bit numbers are demonstrated. On the other hand, the device utilizes the photovoltaic effect in the graphene/Ge heterostructure to generate photoresponse at zero working bias, enabling self‐driven photodetection upon NIR light illumination. The wide‐bandgap Cs 3 Cu 2 I 5 functions as an effective NIR anti‐reflection layer to induce a strong light trapping effect, giving rise to boosted photoresponse properties. The excellent photoresponse supports the device in performing single‐pixel NIR optical imaging. It is believed that this work is inspiring to the design of high‐performance multi‐functional optoelectronic devices toward integrated and intelligence applications.