Study On The Performance Of Phthalocyanine Thin Film Sensor Based On Polymer Insulating Layers

The organic field effect transistor?OFET?has the advantages of simple preparation method,wide material sources and low cost,so the gas sensor with copper phthalocyanine?CuPc?,an organic semiconductor material,as the sensitive layer was prepared by using OFET as the basic structure.The weak epitaxial growth technology,annealing technology,vacuum vapor deposition method,spin coating method and other methods are introduced which to preparate the organic thin film.The main research contents include the types,preparation conditions and methods,film quality and morphology of gate insulation layer;the effect of the insulating layers on organic layers;the insulating layer effect on the performance of the transistors and sensors and response mechanism.And the specific content includes three parts:?1?Silicon nitride?SiN_X?was surface modified with polymethyl methacrylate?PMMA?The single SiN_X insulating layer was modified with PMMA polymer to reduce the surface roughness to 1/5 of SiN_X,which to obtain a high quality CuPc organic semiconductor thin film.The mobility of OFET devices based on SiN_X/PMMA composite insulation layer reached 6.05×10^-3 cm²/V·s,and the switching ratio and saturation current were improved by more than one order of magnitude.Moreover,when the concentration of NO₂ is 20 ppm,the responsivity of gas sensor based on composite insulation layer reaches 1368%and the sensitivity reaches about 61%/ppm.The improvement of OFET device and gas sensor performance is mainly attributed to the modification of PMMA insulator layer,which reduces the electron trap density of single SiN_X insulator device.?2?High performance OFET gas sensor at room temperature was prepared by sol-coating methodIn order to improve the stability and sensing performance of the gas sensor,the Al₂O₃/PMMA composite insulation layer is prepared by sol-coating method with simple operation and low cost,which to obtain the high quality p-hexabiphenyl?p-6P?/CuPc organic thin film.In the condition of the Al₂O₃-sol concentration is 0.8 mol/L,the carrier mobility of composite insulator OFET device is 23 times higher than that of single-layer PMMA device,the threshold voltage is 32.47 V lower,and the switching ratio and saturation current are increased by one order of magnitude.In the room temperature test environment,the composite insulator OFET gas sensor based on Al₂O₃/PMMA has good stability and repeatability,low baseline drift,the minimum detection limit lower than 1 ppm and the maximum detection limit higher than 35 ppm,and its sensitivity reaches 129%/ppm.Compared with single insulation layer,composite insulation layer is more conducive to improving the quality of the organic layer,contributing to the construction of carrier conductive channel,so as to improve the overall performance of the OFET device and sensors.?3?High performance OFET gas sensor was prepared by using all organic materialsThe all structures of OFET devices and gas sensors are made of organic materials except electrodes,include polystyrene?PS?,polyvinyl pyrrolidone?PVP?and PMMA.The surface roughness of the single PS and PVP insulation layer is relatively large,reaching 25.15 nm and11.39 nm,respectively.After the modification by PMMA film,the surface roughness of the prepared composite insulation layer is reduced to less than 2.30nm.It is found that the PS/PVP composite insulating layer structure devices have poor electrical performance and high sensor performance,which is attributed to the gap in PS film which improves the electronic exchange efficiency between NO₂ gas and sensor,but reduces the OFET performance.The all-organic OFET gas sensor provides certain date and theoretical support for the application of sensors in flexible devices and intelligent wearables.