Phosphonic Acid Self-Assembeld Monolayers(SAMs) Applied In N-Type Organic Thin-Film Transistors Based On Naphthalene Diimides(NDIs)

OTFTs are a sort of field-effect devices composed of organic semiconductor materials,metal electrodes and insulating layer,which are critical components of organic integrated circuits(ICs).Recently,the commercialization of organic thin-film transistors(OTFTs)has attracted wide attention because of their potential in next-generation electronic devices such as flexible displays and low-cost radio-frequency identification tags.However,there are still a lot of challenges that applications of OTFTs in the organic ICs,such as n-type organic semiconductor(OSC)materials of high performance and air stability are still very scarce.The main research achievements involved in this thesis are as follows:Three different kinds of phosphonic acid self-assembled monolayers(NAPA,TDPA,ODPA)have been selected to modified insulator surface with Tethering by aggregation and growth method(T-BAG).Then interpreting the basic elements of phosphonic acid self-assembeling on the substrate.By observing the self-assembly films of the contact angle,we found that three phosphoric acid molecules were hydrophobic well to reduce the surface energy of insulator surface.Analysing the AFM patterns of ODPA SAMs,we observed that ODPA formed a tight uniform single layer film on the SiO2 insulating layer.Several naphthalene diimide derivatives were designed and synthesized(NDI-TP,NDI-Cy5,NDI-C8,NDI-C14,NDI-C16).Organic semiconductors materials were determined by thermogravimetric analysis of thermal decomposition temperature(Td),indicating that the several NDI derivatives were not decomposed in evaporation.Cyclic voltammetry curves of NDI derivatives have been surveyed to calculated LUMO energy levels,the results show that the NDI derivatives of LUMO energy levels close to-3.8eV.OTFTs based on NDI derivatives were fabricated with vacuum deposition method.Semiconductor properties of the corresponding OTFTs devices were tested to got the output characteristic curve and the transfer curve,then worked out of OTFTs key performance parameters,including the carrier mobility(?),the threshold voltage(VT)and the current ratio(Ion/off).Compare OTFTs performance parameters,analysis of three kinds of phosphonic acid self-assembled SiO2 insulating layer of surface modified for performance improvement,discussed the substrate temperature(Tsub)impact on device performance.When the Tsub equal to 25?,NDI-C14 shows the optimum carrier mobility up to 5.83×10-2cm2/V?s based on ODPA SAMs at room temperature.It is observed that the device performance enhanced highly significant.Through polycrystalline thin-film XRD morphology of the five NDI derivatives,described the diffraction intensities,d-spacing,width impact on device performance.