The Research Of Organic Thin-Film Transistors With Patternable Polymer Gate Insulator

Organic Thin-Film Transistor(OTFT)has attracted widely concerned and significant attention of people due to the potential applications in flexible electronics,low cost,large area display filed.Thanks to the advantages of solution process,excellent mechanical properties and low-temperature processing,it has become the focus of attention of many researchers and accordingly is being continually studied.With constant development of organic material's performance and optimization of device fabrication process in recent years,the performance of organic thin-film transistors are now comparable to that of a-Si based thin-film transistors.For the manufacture of high performance OTFT,a suitable gate insulator is critical as important as the organic semiconductor itself.The ideal gate insulator should have a high breakdown voltage,good long-term stability,and good adhesion to the substrate.Organic polymers having good processability and dielectric properties,such as poly(vinyl phenol)(PVP),poly(vinyl alcohol)(PVA),poly(methyl methacrylate)(PMMA),and polyimide(PI)have been widely employed as gate insulators.They can be easily formulated into uniform and mechanically flexible layers over a large area.However,for low-cost and large-area applications,polymer gate insulators should be patterned with a high pattern resolution and processed at low-temperature.This paper based on a kind of UV curable polysiloxane material,which has the features of negative photo-resists and can be patterned with a high pattern resolution by using light expose and development.We can use solution process to fabricate gate insulator layer.Firstly,we test the basic properties of this polysiloxane material.Using atomic force microscope(AFM)to measure the surface roughness of this polymer thin film.The result showed it's mean-square value is 0.38m which means the thin film has a plane surface.Insulation property was measured by using a metal-insulator-metal(MIM)structure.The relative dielectric constant is 3.7 and leakage current is?2.6×10^-9A/cm² under an electric applied field of 1MV/cm,which shows that this polysilxone material has good insulating property.Secondly,we use solution process to fabricate OTFT which based on this polysiloxane material and a new type organic semiconductor material.The effects of solution concentration of gate Insulator material,spin-coating rates of OGI,hard-baking temperature of OGI and Organic Semiconductor(OSC),surface treatment of OGI on performance of OTFTs were discussed in detail.Get the best OTFTs performance through optimizing process parameters.Then we compare the OTFT performance with other two which use different polymer material as gate insulators.a discussion of common problems about OTFT performance were included at last.Lastly,OTFT was fabricated on PET flexible substrate based on this polysilxane material and new type organic semiconductor material.And the operating temperature is less than 150?.Meanwhile,detailed preparation method and process parameters were given.The OTFT exhibits a decent mobility up to?0.5 cm²V^-1s^-1,sub-threshold swing down to?1.8 V/dec,on-off ratio higher than 10⁵,gate leakage current density less than?2.28×10^-5 A/cm² under an applied electric field of 1 MV/cm.