Self-Rolled-Up Microtube Optoelectronic Synapse Based on WS2/Graphene Heterojunction for Retina-Inspired Photoresponse Dynamics

Current neuromorphic vision sensors still struggle to accurately emulate the complex and dynamic photoresponse behaviors of the biological retina, limiting their capability to replicate realistic visual perception characteristics. The integration of two-dimensional (2D) materials with self-rolled-up three-dimensional (3D) microtube architectures has emerged as an effective strategy for constructing neuromorphic vision sensors. Herein, we have systematically demonstrated the functional evolution from a planar WS2 photodetector to a 3D microtube WS2/graphene heterojunction optoelectronic synapse capable of emulating the photoresponse dynamics of the retina. Upon integration of a van der Waals (vdW) heterojunction with graphene and in situ self-rolling into a 3D microtube, the device achieves a pivotal functional evolution: the microtube cavity enhances the light-trapping efficiency, while the curvature-induced strain further modulates the energy band and defect states of materials, triggering the hyperpolarization behavior analogous to that of biological photoreceptors and ON-bipolar cells under optical stimulation. The 3D microtube WS2/graphene heterojunction device delivers a biomimetic composite photoresponse, consisting of an initial current dip corresponding to photoreceptors hyperpolarization, a subsequent current rise mimicking the activation of ON-bipolar cells, a fast decay with undershoot reflecting ON-bipolar cells hyperpolarization, and a prolonged slow recovery process analogous to dark adaptation of rod cells. This work mitigates partial functional mismatches between artificial optoelectronic devices and biological retinal cells and provides a viable route to fabricate neuromorphic vision sensors emulating biological photoresponse characteristics.