A reversible and fast-responsive humidity sensor based on a lead-free Cs2TeCl6 double perovskite

Owing to their high conductivity and carrier mobility, the outstanding achievements of lead halide perovskites have been demonstrated in humidity sensor applications. However, the rapid degradation of perovskites upon over-exposure to high humidity as well as the toxicity of lead hinder their large-scale commercial applications. Herein, a lead-free Cs2TeCl6 double perovskite is explored to detect humidity owing to its extraordinary humidity-dependent electrical properties. The Cs2TeCl6 thin film explored as a perovskite-based humidity sensor shows excellent reliability and stability in relative humidity (RH) range from 5% to 90% with a super-fast response (13.8 s) and recovery time (1.39 s). Moreover, the outstanding reversible ability of the developed sensor was achieved when the humidity detector was repaired using HCl gas, thus overcoming the inevitable degradation issue of the perovskite-based sensors, even working in a long-term humidity environment (RH > 90%). Furthermore, the integrated Cs2TeCl6 perovskite-based face mask was used for the real-time monitoring of human respiration, giving a basic human assessment of health status directly and rapidly.