Enhancing the humidity sensing performance of Cs3Cu2Cl5 crystals by formation of heterostructures with metallic NbS2 nanosheets

Apart from their outstanding photoelectronic properties, metal halide perovskites have demonstrated reversible stimuli-responsibility toward a variety of different environmental stimulus. Herein, we used a hot-injection method to deposit lead free perovskite Cs3Cu2Cl5 on layered metal chalcogenide NbS2. The Cs3Cu2Cl5/NbS2 heterostructures and the pure Cs3Cu2Cl5 crystals were fabricated into humidity sensors based on impedance change. The heterostructures exhibited an ultra-high humidity sensing response of up to 104 when the relative humidity (RH) was changed from 11% to 97%, which was at least one order of magnitude higher than that of the pure Cs3Cu2Cl5 crystals. The enhanced performance of the heterostructures was attributed to the improved film continuity and hydrophilicity, which respectively led to the improved charge/ion conduction and increased water adsorption. In addition, the Cs3Cu2Cl5/NbS2 heterojunction is ohmic-like, enabling effective charge/ion transfer across the interface. Given the high RH response of the heterostructures, a contactless sensing device was fabricated, targeting for the vapor emitted from a fingertip. Our work demonstrates that heterostructures between metallic 2D materials and metal halide perovskites are promising sensing materials.