Piezotronic Effect Improved Flexible Humidity Sensing of 2-D MoS2/Ti3C2Tx (MXene) Nanohybrid

This report demonstrates the piezotronic effect on the performance of the flexible humidity sensor based on MoS 2/Ti3C2Tx nanohybrid. The fabricated humidity sensor exhibited excellent reversibility for relative humidity (RH) ranging from 40% to 90%. The fabricated sensor’s sensitivity value without any applied strain and under the applied external strain of ~20% was calculated to be ~0.50571 and ~1.94558, respectively, suggesting an increment in the humidity sensing performance under external strained conditions. The decrement in the sensor current upon humidity exposure is attributed to the decrement in the majority carriers of the Ti3C2Tx p-type. Upon external bending strain, due to the polarization charges created due to the piezoelectric property of MoS2 and also due to the donation of electrons from the water molecules present in the humid environment, the depletion region width extends more toward p-type Ti3C2Tx, which further decreases the sensor current under humid environments. The detailed explanation of piezotronic humidity sensing is explained via band diagrams extracted from the real-time ultraviolet photoelectron spectroscopy (UPS) and the modulation of the depletion region under external strain. The successful demonstration of such flexible humidity sensors opens up new research possibilities in various sectors.