Effect of hydroxyl group in polymeric dielectric layer on the performance of organic thin-film transistors and their application for NO₂ gas sensor

Poly(vinyl alcohol) (PVA) as a conventional polymer dielectric material which possesses excellent insulating performance by cross-linking of the hydroxyl-rich group (-OH) has been utilized extensively in organic thin-film transistors (OTFTs). In this work, a novel strategy for OTFTs, constructing with tandem dielectric films, is studied. The air stability of OTFTs can be conveniently modulated by the construction of tandem dielectrics. Herein, with the optimization for the dielectric structures and interface engineering, a holistic understanding of the hydroxyl group for the performance of OTFTs and OTFT-based gas sensors is provided. Implementing the interface properties affords double dielectric OTFTs that deliver a remarkable responsivity for 10 ppm NO₂ nearly 62% and triple dielectric OTFTs that maintain a slight fluctuation in their electrical performance during 10-day atmospheric storage, respectively. The enhancement of air stability of OTFTs and sensing performance for NO₂ can be attributed to the passivation controlling effect of PVA, and these results demonstrate that the simple and effective method provides new insight into the design of functional groups of organic dielectric materials for high-performance, air-stable OTFTs and high responsivity for OTFT-based gas sensors.