In Situ Selenization‐Enabled PdSe ₂ Homojunctions for Ultrahigh Polarization Sensitivity and Rapid Broadband Photodetection

Abstract This study demonstrates a breakthrough in fabricating high‐performance PdSe 2 homojunction photodetectors via an innovative mechanical exfoliation combined with in situ selenization strategy. By precisely controlling the thickness of n‐type PdSe 2 (20 nm), the optimized device achieves good broadband detection (532–2200 nm) with favorable performance metrics. Polarization sensitivity with Extinction ratios of 137.5@532 and 126.5@1310 nm, surpassing existing 2D‐based detectors by >27×, rapid response with 10 µs rise time and 58 µs fall time at −2 V, addressing the slow response (>10 µs) of conventional PdSe 2 devices, and outstanding responsivity of 0.895 A/W@532 and 0.112 A/W@1310 nm under −2 V, are achieved attributed to enhanced built‐in electric fields and carrier separation efficiency. Kelvin probe force microscopy (KPFM) confirms a strong built‐in potential (230 mV) at the homojunction interface, while thickness‐dependent studies reveal that thinner n‐PdSe 2 layers amplify n‐type behavior and reduce carrier diffusion paths. The device further exhibits linear photocurrent‐power dependence (θ≈1), high specific detectivity (1.04 × 10 8 Jones), and robust infrared imaging capability. Furthermore, a polarization‐modulated optical communication system is implemented. This work provides a scalable platform for developing high‐speed, polarization‐resolved photodetectors in next‐generation intelligent sensing systems.