All-inorganic lead-free halide perovskite Cs2TeBr6 enables real-time touchless human breath and finger related humidity monitoring

Halide perovskite (HP) materials have attracted much attention in recent years in the fields of smart home and medical detection due to their low fabrication cost, simple preparation process, controllable properties, and adjustable morphology. However, the inherent instability and toxicity of lead has been barriers limiting the practicality in electronical devices. Here, we demonstrate a high-performance impedimetric humidity sensor based on an all-inorganic lead-free HP Cs2TeBr6 for the first time. The Cs2TeBr6 sensor achieves ultra-high response value of 5 orders of magnitude (8.89 × 105) at 11–97 % relative humidity (RH), short response time (4 s), favorable repeatability, and good long-term stability. Moreover, high humidity sensing performance enables the Cs2TeBr6 sensor to enjoy great potentials in real-time touchless human breath and finger detections. In addition, the mechanism of moisture sensitivity is explained by complex impedance spectra at different humidity levels. This work contributes an attracting candidate material for humidity sensors, and furthermore provides new insights into next-generation sensory devices using lead-free HPs for human-related detections.