Trap‐Mediated Spectral Shaping in Sb ₂ Se ₃ /Au van der Waals Junction for Turbid‐Water Communication and High‐Precision Artificial Vision

ABSTRACT Near‐infrared narrowband photodetection is indispensable for high‐fidelity optical communication and sensing, yet conventional filter‐based architectures suffer from intrinsic drawbacks in integration, stability, and spectral purity. Here, we circumvent these constraints by constructing a filter‐free, self‐powered ultra‐narrowband near‐infrared photodetector based on a van der Waals (vdWs) junction between 2D Sb 2 Se 3 and Au. The vdWs contact effectively suppresses Fermi‐level pinning, approaching the Schottky‐Mott limit and enabling ultralow interface resistance. The device delivers a sharp responsivity peak at 1020 nm with a record‐narrow linewidth of 46 nm, achieving a responsivity of 195.7 mA/W and a specific detectivity of 7.74×10 11 Jones under zero bias. Through controlled thermal annealing, we unveil defect‐engineered spectral shaping that progressively narrows the response from 247 to 46 nm, directly implicating trap states in photoconversion dynamics. Exploiting strong in‐plane anisotropy of Sb 2 Se 3 , the detector exhibits a polarization anisotropy ratio exceeding 16. Beyond characterization, we demonstrate a quaternary polarization‐encoded optical communication system operating reliably in highly turbid water (500 NTU), and achieve 98.2% image recognition accuracy via convolutional neural networks. This work intrinsically integrates narrowband filtering and polarization sensitivity at the device physics level, establishing a transformative paradigm for next‐generation multifunctional photodetectors free of external optical elements.