Collaborative Enhancement of Humidity Sensing Performance by KCl-Doped CuO/SnO(2) p–n Heterostructures for Monitoring Human Activities

[Image: see text] In this study, a high-performance humidity sensor based on KCl-doped CuO/SnO(2) p–n heterostructures was fabricated by a ball milling–roasting method. The morphology and nanostructure of the fabricated KCl-CuO/SnO(2) composite were characterized by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and nitrogen sorption analysis. The results showed that the humidity sensor had a high sensitivity of 194 kΩ/%RH, short response and recovery times of 1.0 and 1.5 s, a low hysteresis value, and good repeatability. The energy band structure and complex impedance spectrum of the KCl-CuO/SnO(2) composite indicated that the excellent humidity sensing performance originated from the ionic conductivity of KCl, the formation of heterojunctions, the change in the Schottky barrier height, and the depletion of electronic depletion layers. The KCl-CuO/SnO(2) sensor has great potential in respiratory monitoring, noncontact sensing of finger moisture, and environmental monitoring.