Nanofiber-Textured Organic Semiconductor Films for Field-Effect Ammonia Sensors

Field-effect gas sensors, integrating the gas sensor and amplification transistor, exhibit excellent sensory performance. Here we report organic thin-film transistors (OTFTs) with nanofiber-textured semiconductor films that exhibit superior ammonia response compared to conventional OTFTs with uniform/flat semiconductor films. The introduce of insulating polymer additives (IPAs) facilitates the formation of semiconducting nanofiber during coating. The effects of IPAs, organic semiconductor/IPA blend ratios and solvents on OTFT-based sensory performance are studied. The results show that the use of SU8 as IPA and chloroform as solvent form intertwined semiconductor nanofibers (∼50 nm in diameter) at the bottom. The resulting OTFTs exhibit extraordinarily high sensitivities to ammonia, which reach 13676%/ppm (current) and 457%/ppm (turn-on voltage), respectively. Finite element analysis was conducted to simulate the adsorption/desorption processes of gas molecules and the roles of specific surface area on sensory performance.