BiOI: Self‐Powered Humidity Sensor and Breath Monitor

Abstract The self‐powered, adaptable, quick, and precise humidity sensors are required to measure humidity in the microenvironment. Here, a simple one‐step wet chemical method is presented to prepare stacked layered bismuth oxyiodide (BiOI) nanoplates. The remarkable response and self‐powered behavior of BiOI nanoplates‐based humidity sensors are demonstrated for the first time. The humidity sensing characteristics of BiOI are examined within the range of 30–80% relative humidity (RH) at an operating temperature of 323 K. The highest sensitivity level of 39 kΩ per %RH is determined for a relative humidity of 75.5%. A successful attempt is made to use this sensor as a human breathing process monitor. The sensor response times at room temperature in this test are 3.04(9) s at 0 V and 3.31(7) s at 20 V, whereas the recovery times are estimated to be 6.57(6) s at 0 V and 6.42(4) s at 20 V. Future advancements in sensing devices utilizing BiOI hold the potential to yield highly responsive, ultrafast sensors with simplified device geometries, and self‐powered.