Synergistic dual built-in electric fields enabled self-powered humidity sensors based on MXene/MoS2 van der Waals heterostructures

Abstract

Developing zero-power humidity sensors is critical to overcoming battery limitations in wearable health monitoring. Here, we report a high-performance self-powered humidity sensor based on MXene/MoS2 van der Waals heterostructures. A thickness gradient in the chemical vapor deposition-grown MoS2 film creates a stable in-plane built-in electric field, while the work function difference between MXene and MoS2 forms a Schottky junction that suppresses dark current and boosts the signal-to-noise ratio. In a humid environment, the super-hydrophilicity of MXene induces moisture-mediated charge transfer and electron injection. The vertical interfacial field efficiently pumps electrons into the MoS2 channel, where they subsequently undergo directional drift driven by the in-plane built-in field, generating a stable direct current output. The sensor exhibits excellent linearity (R2 > 0.99) and ultrafast response/recovery. It enables high-sensitivity monitoring of human respiration and voiceprint characteristics. This dual-field synergistic mechanism offers a promising strategy for next-generation low-power, high-sensitivity environmental and health-monitoring microsystems.