Research On Gate Insulator Layer Of Organic Thin Film Transistor

Though there are many reports on the preparation of organic insulator layers, the research on the influence of ITO to the organic film property is rare. In this thesis, two organic insulators were prepared on ITO substrates. The surface morphologies, electrical properties and leakage mechanism of insulator were investigated.Firstly, the surface roughness and hydrophilicity of the ITO which was modified with Phenyl phosphonic acid were measured; secondly, we prepared PMMA and PVP insulator layers on the ITO substrate by spin-coating, detecting the influence of ITO modification to the surface morphologies and the electrical properties of PMMA and PVP. We analyzed the effect of molecular weight on PMMA, and the cross-linking agent mass fraction on PVP. The leakage mechanism of PMMA and PVP were also discussed in the thesis.The research indicates that 2-hours was the ideal time to get the best surface of the ITO, the roughness and leakage current of the insulator layers reduced obviously after the ITO was modified, and electrical properties were more stable. PMMA with different molecular weight had similar leakage mechanism: in the voltage range of 0-6V, 6-10 V, 10-15 V, the main mechanisms were P-F effect, Schottky emission and space charge limited current respectively. Films with mass fraction of both PVP and cross-linking agent were 5% had lower leakage current and higher reliability. When mass fraction of cross-linking agent were 3%, 5%, 7%, the leakage mechanism of PVP changed from P-F effect to Schottky emission at 10.3V, 10.8V and 10 V respectively.PMMA and PVP prepared by the method in the thesis had lower surface roughness and the films quality were better; the leakage currents at the magnitude of 10-8A/cm2 were observed, capacitance of PMMA with the molecular weight of 350 k reached 10.75nF/cm2. PVP films under the condition that the weight percentage of both PVP solution and cross-linking agent had capacitance of 19.0nF/cm2, and electrical properties of the insulator layers were stable. The film of PVP and PMMA can be used in the preparation of OTFT or other photoelectric devices.