Fabrication and Characterization of P3HT/MoS₂ Thin-Film Based Ammonia Sensor Operated at Room Temperature

Abstract

The composites of polymers and two-dimensional (2D) materials show promising applications in the area of gas sensing. In this work, we report an efficient ammonia gas (NH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) sensor based on poly(3-hexylthiophene)/ molybdenum disulfide (P3HT/MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) nanocomposite. The sensing device has been fabricated in bottom-gate top contact organic field-effect transistor (OFET) assembly using P3HT/MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> as active channel material. The changes in the electrical response of OFET has been measured and analyzed for various ammonia gas concentration at room temperature. The sensing device in the form of an OFET structure is preferred due to multi-parameter characteristics to explore gas sensing applications. The active sensing layer has been fabricated via a self-assembled, cost-effective floating film transfer (FTM) technique. An optimized uniform sensing film of thickness 25±3 nm is used to analyze the change in the electrical characteristic of the device in terms of I/O characteristics, mobility, threshold voltage, trapped charge density, etc., for various ammonia concentrations. The OFET with nanofiber morphology of mobility 0.147 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /V-s shows the threshold voltage of −3.78 V (in the air) and changes to −10.71 V after 100 ppm ammonia gas exposure. The device has shown a limit of detection (LOD) of 904 ppb and a sensing response of 63.45% at 100 ppm ammonia concentration. The extraction of multi-parameter sensing characteristics of the device has been conducted in a closed chamber with an ambient environment. The fabricated sensor is therefore having potential applications in high-performance ammonia sensing applications.