Influence Of Solvent On The Gas Sensing Properties Of Organic Thin-Film Transistors

Recently,the strong and controllable chemical sensitivity of organic semiconductors?OSCs?functional layers and the amplification capability of transistors make use of organic thin-film transistors?OTFTs?compelling for circuits,physical,biological,and chemical sensors in wearable devices and other electrical applications which have attracted a numerous attraction and become essential components in modern organic electronics.Besides,OTFT-based gas sensors have the characteristics of flexible design,high integration,large-signal multiplication,and multi-electronic parameters for the detection and analysis of toxic and harmful gas atoms or molecules which may adversely affect human's health.They have a great significance and broad application prospect in the field of dangerous gas detection and biomedicine.In the past few decades,researchers had focused on the chemical structure modification of sensitive materials,the morphology control of OSCs films and the optimization of the interface between organic functional layers to enhance the detection performance.Also,they can realize multi-parameter detection by OTFT as a signal converter or signal amplifier.Therefore,with the perspective of OTFT application and development,we first studied the intrinsic correlation between the morphology of OSCs films and gas-sensitive responses in OTFT devices.And then,we introduced a high-efficiency but simple solution method which could optimize the growth of OSCs,adjust their crystallinity and grain boundaries,and achieve high performance and excellent responsivity of OTFT-based gas sensors.Finally,the effect of hydroxyl group in the polymeric dielectric layer on the stability of OTFT-based gas sensors was further studied.It also paved a new way to understand the high-reliability OTFT-based devices.The main works included three parts are as follows:1.The effects of diverse polar organic solvents on the crystallinity and grain boundary density of OSCs were studied.Based on the diverse polar organic solvents having different boiling points,polarities and solubility for OSCs materials,6,13-bis?triisopropylsilylethynyl?pentacene?TIPS-pentacene?with different degrees of crystallinity and grain boundary density was prepared by diverse organic solvents.Owing to the different states of OSCs films by solvents,it not only provided us an effective morphology control strategy for OSCs but also paves the way for its application in OTFT-based devices.2.The effects of distinct crystallinity and grain boundary density of OSCs films on the performance and gas-sensitive characteristics of OTFT-based devices were investigated.Based on the different crystallinity and grain boundary density of TIPS-pentacene film by diverse solvents,OTFT-based gas sensors with excellent performance and high responsivity to NO₂ were prepared.Particularly,o-xylene is the ideal organic solvent for optimizing the crystallinity and grain boundaries of TIPS-pentacene OSCs.Under 10ppm NO₂ atmosphere,the responsivity of OTFT-based sensors treated with o-xylene is58 times than that with chlorobenzene.Besides,we combined the morphology,crystal structure,and surface chemical groups to analyze and understand the gas sensing mechanism.3.The effects of organic polar polymeric dielectric materials on the gas sensitivity and environmental stability of OTFTs were analyzed.Based on the optimization of dielectric layered structure and interface engineering,the tandem dielectric structures were used to achieve high mobility of 0.085 cm²V^-1s^-1and a high responsivity of NO₂ near 62%within 10 ppm NO₂ atmosphere in OTFT-based sensors.Moreover,through the passivation control of conventional polar polymeric dielectric materials,the environmental stability control of OTFT-based gas sensors under long-term storage in air was realized,which provided a new sight for the structural design of high-performance organic dielectric materials.In summary,we studied the influence of organic solvent on the crystallization of organic semiconductors and its influence on the performance of OTFT-based devices and their sensing properties.Meanwhile,based on the contact interface and the polar functional groups of dielectrics,the effect of polar groups on the sensing properties have been studied.This work will provide effective strategies to the stability and performance optimization of OTFT-based gas sensors.