Synergistic UV and humidity response of flexible MoS2/Kapton heterointerfaces via photogenerated charge transfer

Abstract

Realization of high-performance optoelectronic and gaseous sensing with excellent mechanical flexibility may open up broad multifunctional applications, such as wearable smart sensor systems, robust environmental/infrastructure monitoring, and personal health monitoring with human-friendly interfaces. Here, we proposed a flexible MoS₂/Kapton sensor with synergistic optical UV and humidity functionalities. Because of its ultrathin monolayer, the electrical transport of the 2D MoS₂ channel tends to be affected by both the surface and interface states. The photogenerated charge transfer plays a synergistic role in both the UV and humidity sensing by utilizing band alignment engineering. On the one hand, the photoabsorbing Kapton substrate forms a photogating heterointerface with the 2D MoS₂ monolayer to greatly strengthen the photogenerated charge transfer. Under 325 nm UV photoexcitation, the flexible MoS₂/Kapton sensor has achieved a best photocurrent to dark current ratio of 3.87 × 10⁵. On the other hand, the 2D MoS₂ monolayer has a large surface area for the effective adsorption of water molecules. The UV photogenerated charge transfer is beneficial to boost up the relative humidity (RH) response range above 10⁵ for humidity sensing. As a result, flexible MoS₂/Kapton heterointerfaces enable high-performance multifunctional sensing for promising 2D/3D heterogeneous integration.