Fabrication And Gas Sensing Properties Of Field Effect Devices Based On Ion Gel Dielectric Layer

In recent years,organic field effect transistors(OFETs)have attracted the attention of many researchers due to their low cost and simple preparation process.At present,the performance of some OFETs have exceeded amorphous silicon transistors and are used in many places.Such as logic circuits,flexible electronics,sensors,and so on.In this paper,polyethylene terephthalate(PET)film is used as the substrate,organic polymer material poly(3-hexylthiophene(P3HT)is used as the semiconductor layer,and organic conductive material poly(3,4-ethylenedioxythiophene): Polystyrene sulfonic acid(PEDOT:PSS)is used as the source drain,silver wire is used as the gate electrode,ionic liquid is mixed with polymethyl methacrylate(PMMA)as the insulating layer,combined with screen printing process,spin coating and An organic field effect transistor device was prepared by means of a gas spray coating.The ionic liquid is a novel polymer electrolyte material with a high dielectric constant.The high dielectric constant is mainly due to the formation of an electric double layer(EDL)capacitance at the interface between the electrolyte and the semiconductor.In the prior literature,the capacitance of the EDL is generally considered to be a fixed value,but in this experiment it was found that the EDL capacitance is related to the electrode potential,and the conductivity parameter of the semiconductor channel decreases as the gate voltage decreases.To check for changes in interface capacitance at different gate voltages,we measured the impedance of the entire transistor at different bias voltages and applied an equivalent circuit model to extract the differential capacitance.According to Kornyshev theory,the reduced EDL capacitance is related to the finite ion volume in the ionic liquid gel.Finally,the device was applied to the gas sensor,and the response and recovery of the device to NO2 gas was tested.It was found that the device had a large response after inletting NO2 was applied without the gate voltage,but the air did not recover.Then,it is found that with the increase of gate voltage,the device has a recovery trend.Considering that the ion gel has a certain adsorption capacity,NO2 is adsorbed in it.Increasing the gate pressure will provide an electric field force for the ion gel to make adsorption.The gas can be partially desorbed,but too high a gate voltage can damage the device and all require a suitable transistor bias.In summary,this paper firstly used an ionic liquid electrolyte to prepare an OFET device.It was found that the EDL capacitance changes with the bias voltage,and the conductivity of the channel decreases with the increase of the gate voltage.Secondly,the gas sensing properties of the device were studied.It was found that the gate pressure has a great influence on the gas adsorption process of the ion gel.The specific gas sensing process needs further study.