Perovskite‐Induced Ultrasensitive and Highly Stable Humidity Sensor Systems Prepared by Aerosol Deposition at Room Temperature

A new capacitive‐type humidity sensor is proposed using novel materials and fabrication process for practical applications in sensitive environments and cost‐effective functional devices that require ultrasensing performances. Metal halide perovskites (CsPbBr 3 and CsPb 2 Br 5 ) combined with diverse ceramics (Al 2 O 3 , TiO 2 , and BaTiO 3 ) are selected as sensing materials for the first time, and nanocomposite powders are deposited by aerosol deposition (AD) process. A state‐of‐the‐art CsPb 2 Br 5 /BaTiO 3 nanocomposite humidity sensor prepared by AD process exhibits a significant increase in humidity sensing compared with CsPbBr 3 /Al 2 O 3 and CsPbBr 3 /TiO 2 sensors. An outstanding humidity sensitivity (21426 pF RH% −1 ) with superior linearity (0.991), fast response/recovery time (5 s), low hysteresis of 1.7%, and excellent stability in a wide range of relative humidity is obtained owing to a highly porous structure, effective charge separation, and water‐resistant characteristics of CsPb 2 Br 5 . Notably, this unprecedented result is obtained via a simple one‐step AD process within a few minutes at room temperature without any auxiliary treatment. The synergetic combination of AD technique and perovskite‐based nanocomposite can be potentially applied toward the development of multifunctional sensing devices.