Low-Temperature Growth of High-Quality Bi₂O₂Se Nanosheets Enabling Weak-Light Detection with Ultralow Dark Current

Bi₂O₂Se is an emerging n-type semiconductor, but conventional growth methods often rely on high temperatures or complex multisource systems that introduce defects and limit device integration. Herein, we report a simplified and modified physical vapor deposition (PVD) strategy enabling the growth of single-crystal Bi₂O₂Se nanosheets at a lower temperature of 500 °C. The self-powered photoelectric detector with an asymmetric structure was fabricated using a Bi₂O₂Se nanosheet as channel material, exhibiting an ultralow dark current of ∼10 fA, weak-light detection capability (50 nW/cm²), and detectivity up to 1.06 × 10¹³ Jones. The devices also show fast response time and excellent long-term stability with <10% degradation after 12 months in the atmospheric environment. Furthermore, single-pixel imaging demonstrates high contrast and fidelity. This work establishes a practical route for low-temperature growth of high-quality Bi₂O₂Se nanosheets and highlights its strong potential for weak-light detection, broadband sensing, and chip-scale photonic systems.