Research On The Performance Of Field Effect Transistors Based On Polymer/Silica Composite Film Insulation Layers

Organic field effect transistors(OFET)have the advantages of light weight,low price,simple process,and flexible bending.They have important applications in active matrix organic light emitting diode displays,radio frequency identification tags,flexible wearable devices and other fields.The polymer has good stretchability,film-forming properties and compatibility with organic materials.And it can be used for the insulating layer of OFET.Heterogeneous induction is a method for preparing high-quality organic semiconductor thin films.The combination of polymer insulating layer and heterogeneous induction method will help improve the performance of the OFET devices.Therefore,this thesis studied the effect of different polymer composite insulating layers on the heterogeneously induced growth of hexabiphenyl(p-6P)zinc phthalocyanine(ZnPc)film.The main works are as follows:(1)The influence of p-6P heterogeneously induced ZnPc growth process conditions on film morphology and OFET device performance was studied.The increase of the growth temperature and thickness of p-6P films can make p-6P grains generate large-size,high-coverage crystalline film,which is beneficial to induce the orderly growth of ZnPc molecules.The increase in the growth temperature of ZnPc films is conducive to improving the order of crystals and reducing the generation of grain boundaries.The increase in thickness of ZnPc films is conducive to obtaining more carriers and improving the performance of OFET devices.(2)The effect of polymethylmethacrylate(PMMA)film preparation process conditions on the heterogeneously induced growth of p-6P/ZnPc organic semiconductors was studied.The PMMA/Si O₂ composite insulating layers were prepared by spin-coating PMMA films on silicon dioxide(Si O₂)substrates with different process conditions.As the concentration of PMMA solution increases,the surface roughness of the insulating layer is effectively reduced,and a smooth composite insulating layer is obtained.At the concentration of 10 mg/m L PMMA,p-6P/ZnPc films can form highly ordered crystal domains.As the speed of PMMA spin-coating increases,the surface roughness of the composite insulating layer is also reduced,and the capacitance of the insulating layer is increased.The XRD characterization confirms that p-6P/ZnPc has better crystallinity at high rotation speed of PMMA spin-coating.However,the composite insulating layers formed at a very high rotation speed of 4000 rpm begin to appear hole-like defects.Therefore,when the PMMA concentration is 10 mg/m L and the spin-coating speed is 3000rpm,high-quality p-6P heterogeneously induced ZnPc films can be obtained,and the OFET devices have better performance.(3)In order to further improve the performance of OFET devices based on polymer composite insulating layers,the effect of composite insulating layers prepared by blending PMMA and other polymers on p-6P/ZnPc films of heterogeneously induced growth and the performance of OFET devices was studied.Blended solutions were formed by adding Polystyrene(PS),polyvinylidene fluoride(PVDF)and polyvinylpyrrolidone(PVP)polymers to PMMA solution separately.The different composite insulating layers were formed by spin-coating method on Si O₂ substrates.The PMMA:PS films present spherical protrusion morphologies.The PMMA:PVDF films have needle-like protrusion morphologies.And the PMMA:PVP films present porous morphologies.The surface morphology changes with the blended ratio.The capacitances of PMMA:PVDF composite insulation layer have been significantly improved.The p-6P/ZnPc films form strip or rod-like crystals on the composite insulating layers.Research on the electrical properties of OFET devices found that the threshold voltages of OFET devices based on PMMA:PS and PMMA:PVDF insulating layers were significantly reduced at higher doping ratios of PS and PVDF polymers.It is beneficial to reduce the power consumption of the devices and save energy.