2D Vertical Heterojunction with Codirectional Built-in Electric Fields and Plasmonic Hot-Electron Effect for Broadband Photodetection and Low-Power Visual Synapses

Two-dimensional (2D) vertical heterojunctions, characterized by atomic-scale van der Waals interfaces that facilitate efficient vertical charge transport, offer a promising architecture for integrating self-powered photodetectors (sense) with neuromorphic synapses (think) to achieve an integrated sense-think functionality. However, the interface-induced opposing electric fields and limited spectral response restrict their development. In this study, we address these limitations through a graphene (Gr)/WSe₂/Ag vertical heterojunction architecture. This design synergistically combines minimized carrier transport distance to reduce recombination losses, codirectional built-in electric fields derived from surface potential differences to enhance carrier separation, and plasmonic hot-electron effect to extend spectral response. The optimized heterojunction delivers a remarkable performance. Under 405 nm light of identical optical power intensity, its vertical structure and codirectional built-in electric fields yield a 10.69-fold increase in photocurrent density (J). The generation of plasmonic hot electrons produces a 35-fold increase in J under 1064 nm light of the same power intensity while enabling the successful detection of 1550 nm light. More significantly, the heterojunction exhibits ultralow-power synaptic behavior, with energy consumption ranging from just 0.42 to 320 pJ across visible to near-infrared wavelengths (405-1550 nm). Owing to the excellent self-powered broadband photodetection performance and low-power visual synapses of 2D vertical heterojunctions with co-oriented built-in electric fields and plasmonic hot-electron effect, they hold great potential in ″sense-think″ intelligent devices.