Fast-response humidity sensors based on all-inorganic lead-free Cs2PdBr6 perovskite integrated with bulk acoustic wave resonators for motions monitoring

Halide perovskites have arisen extensive concerns due to their distinguished achievements in optoelectric fields. However, the intrinsic toxicity of lead and instability have limited their applications in humidity sensing. Herein, all-inorganic lead-free Cs2PdBr6 perovskite incorporated with a bulk acoustic wave resonator for humidity detection is demonstrated for the first time. The proposed sensor exhibits faster response and recovery speed than most other perovskite-based humidity sensors, indicating its potential utilization in real-time monitoring of body movements. Apart from that, the perovskite-based sensor shows remarkable logarithmic linearity response as well as superior repeatability and stability in the relative humidity range of 11%-85%. Owing to its fast response and good stability, the sensor is successfully applied in finger movements monitoring, suggesting the potential of application in human-machine interactions. Furthermore, the underlying sensing mechanism of the sensor is analyzed by the Langmuir adsorption model and density functional theory. Therefore, above results have demonstrated the feasibility of perovskite for humidity detection and more perovskites with similar structures could be also be utilized for further exploration.