Study Of Octithiophene Or Reduced Graphene Oxide Doped Organic Thin Film Transistors Gas Sensors

In this paper,the organic thin film transistor with a bottom gate,bottom contact structure is used as the gas sensor.The p-type semiconductor material α-8T is used as the gas-sensing material for the first time,and the sensitive films are prepared by doping the α-8T or RGO into the P3 HT material.What’s more,the electrical characteristics,sensitive characteristics and gas sensing mechanism of OTFT gas sensors were systematically analyzed.The main contents of the paper are as follows:1.A series of P3HT-α-8T composite film device with different film thicknesses and different ratios of mass,and different film structures were fabricated and investigated.Among the four structures films,the composite thin film OTFT has the best electrical and gas sensing properties.The results show that the Vth of P3HT-α-8T-TFT exhibited more positive with the increament of α-8T doping amount and its film thickness,and its Ids and μ are also increasing.In addition,the sensitive responses of the above OTFT gas sensor to NH3 gas were researched.The results show that the P3HT-α-8T-TFT is more stable than the P3HT-TFT device,and it also has the fastest response speed and recovery rate.Among them,the mass ratio of the highest sensitivity device is 2:1,and its gas injection volume is 1ml,and the repeatability of this device is 95.8%.In addition,the gas sensitivity of the sensor to low concentrations of NH3 was also measured,and the response of P3HT-α-8T-TFT to 5 ppm NH3 was 9%.Combined with the characterization of the film,the reason of the carrier mobility increase and the gas sensing mechanism were also analyzed.2.Two P3HT-RGO composite thin film OTFT with different RGO concentrations and a P3HT-TFT gas sensor were prepared.The results showed that the composite film OTFTs have higher Ids than P3HT-TFT,and with increament of RGO concentration in the composite film,Vth shifted more positively,and Ids and μ of the OTFT increase gradually.The gas sensitivity of these OTFT gas sensor to 0~25ppm and 20~100ppm NH3 were investigated.The results showed that the response and sensitivity of NH3 increased after dopinp RGO,and they showed better recovery performance especially to low concentrations(0~15ppm)NH3.3.3×2 OTFT gas sensor arrays with different channel widths and lengths are designed.The experimental steps of preparing OTFT arrays by photolithography,magnetron sputtering,vacuum evaporation,stripping and dicing are described in detail.