Enhanced Responsivity and Photostability of Cs3Bi2I9‐Based Self‐Powered Photodetector via Chemical Vapor Deposition Engineering

Lead‐based halide perovskites have gained significant prominence in recent years in optoelectronics and photovoltaics, owing to their exceptional optoelectronic properties. Nonetheless, the toxicity of lead (Pb) and the stability concern pose obstacles to their potential for future large‐scale market development. Herein, stable lead‐free Cs3Bi2I9 (CBI) films are presented with smooth and compact morphologies synthesized via chemical vapor deposition (CVD), demonstrating their application as an UV photodetector in a self‐powered way. The self‐powered photodetectors (SPDs) exhibit remarkable characteristics, including a responsivity of 1.57 A W−1 and an impressive specific detectivity of 3.38 × 1013 Jones under the illumination of 365 nm at zero bias. Furthermore, the SPDs exhibit a nominal decline (≈2.2%) in the photocurrent under constant illumination over 500 h, highlighting its impressive long‐term operational stability. Finally, the real‐time UV‐detection capability of the device is demonstrated by measuring the photocurrent under various conditions, including room light and sunlight at different times. These findings offer a new platform for synthesizing stable and high‐quality perovskite films, and SPDs for advancing the development of wearable and portable electronics. A self‐powered UV photodetector is developed using lead‐free, all‐inorganic cesium bismuth iodide (Cs3Bi2I9) perovskite films through engineered chemical vapor deposition (CVD). The resulting photodetector demonstrates a responsivity of ≈1.57 A W−1 and a specific detectivity of ≈3.38 × 1013 Jones under UV illumination. It exhibits excellent moisture resistance and long‐term stability, enabling real‐time UV light detection in sunlight.