Lead‐Free Cs2BiAgBr6 Double Perovskite‐Based Humidity Sensor with Superfast Recovery Time

Abstract Lead halide perovskites have demonstrated outstanding achievements in photoelectric applications owing to their unique properties. However, the moisture sensitivity of lead halide perovskite has rarely been developed into an applicable humidity sensor due to the intrinsic instability and toxicity issue. Herein, as a highly stable lead‐free perovskite, a Cs 2 BiAgBr 6 thin film is chosen to be the active material for humidity sensor due to its extraordinary humidity‐dependent electrical properties and good stability. This Cs 2 BiAgBr 6 thin film humidity sensor demonstrates a superfast response time (1.78 s) and recovery time (0.45 s). The superfast response and recovery properties can be attributed to the reversible physisorption of water molecules, which can be easily adsorbed onto or desorbed from the thin film surface. Moreover, the sensor also shows an excellent reliability and stability properties as well as logarithmic linearity in a relative humidity's range of 15% to 78%. The lead‐free Cs 2 BiAgBr 6 perovskite possesses great potential for application in real‐time humidity sensing.