Anisotropic Lead‐Free CsCu ₂ I ₃ Based Optoelectronic Synapse for Polarization‐Sensitive Neuromorphic Vision

ABSTRACT Polarization provides a critical yet often overlooked dimension of visual information, enabling enhanced perception of scattering, object orientation, and material anisotropy. However, conventional polarization‐sensitive photodetectors are limited to passive sensing and lack the capability directly encode and retain polarization information in a neuromorphic manner. Here, we report a polarization‐sensitive optoelectronic synaptic device based on lead‐free anisotropic CsCu 2 I 3 single crystals. Benefiting from the intrinsic one‐dimensional chain‐like crystal structure of CsCu 2 I 3 , the device exhibits pronounced polarization‐dependent photoresponses with a high dichroic ratio of up to 2.71, together with broadband UV–Vis sensitivity. More importantly, the polarization state of incident light directly modulates the synaptic response (ΔEPSC), enabling device‐level coupling between polarization‐sensitive photodetection and synaptic‐state modulation. The device successfully emulates essential synaptic behaviors, including pair‐pulse facilitation and spike‐dependent plasticity modulated by pulse width, frequency, intensity, and number. In addition, polarization‐dependent image reconstruction and contrast enhancement are demonstrated based on the experimentally measured polarization‐dependent synaptic responses. This work establishes anisotropic lead‐free halide single crystals as a promising material platform for energy‐efficient and polarization‐aware neuromorphic optoelectronic devices.