The Research Of Gate Insulating Layer Of Pentacene-Based Organic Thin Film Transistor

At present,the work of scientific research and application of organic semiconductor materials has been achieved fruitfully.Organic thin-film transistor?OTFT?has lots of advantages,such as a low requirement for preparation technology,a low price,and compatibility with flexible transistor and so on.In the future,it will play a unique role in the full organic flat panel display,flexible devices,optical communication field.Though there have many studies of organic thin-film transistor in the world,there are still some problems in OTFT.For example,the lower carrier mobility,high threshold voltage and the relatively poor stability.The selection of the gate insulating layer materials,the film surface morphology,the thickness and other factors have greater impact on the performance of OTFT,it has become a hot research direction in recent years.Under this research background,we optimized the preparation process of ITO gate electrode and fabricated three different gate insulating layers on OTFT,the corresponding OTFT performance was studied in the following aspects:Firstly,the ITO gate electrode preparation process was optimized through wet etching process.ITO conductive glass substrate was etched by thick photoresist lithography UV-light,through changing the exposure time,developing time and etching time,et al.to discuss the influence of these factors on ITO gate electrode etching morphology.We also used phenyl phosphinic acid to modify the surface of the gate electrode,a optimized process conditions of wet etching ITO gate electrode were obtained.Secondly,using polymethyl methacrylate?PMMA?as an organic insulating layer of pentacene-based OTFT by solution spin-coating method,the relationship between different PMMA concentration and film thickness was studied,then analyzing the surface morphology and roughness of the films under different annealing conditions.The result shows that the best electrical properties of the device were obtained when the PMMA concentration was 20mg/ml and annealed at 100°C for 60min.A high K tantalum pentoxide?Ta₂O₅?gate insulating layer of pentacene-based OTFT was made by vacuum evaporation method,the influence of different Ta₂O₅ thickness of OTFT were studied.The result shows that the best electrical properties of the device were obtained when the Ta₂O₅ thickness was 160nm.Finally,a double Ta₂O₅-PMMA insulating layer of pentacene-based OTFT was made.The influence of different thickness of PMMA on Ta₂O₅ surface on the performance of OTFT were studied.By comparing the different topography and roughness of signal Ta₂O₅ or PMMA and Ta₂O₅-PMMA insulating layers,the experiment showed that the best Ta₂O₅-PMMA insulating layer device field effect mobility was increased to 0.31cm²/V·s and the threshold voltage was reduced to-3.8V,the on/off current ratio was 2.9×10⁵.