The Fabrication And Application Of Ambipolar Organic Thin Film Transistors

Since the 1980s, the researches of organic field-effect transistors have attracted great attention. A field-effect transistor not only is a new generation of cheap and flexible unit for build the foundation of organic circuit module, but also provides an important perspective to understand charge transfer in the π-conjugated systems. As a result, they play an important role on exploring π-conjugate system of the relationship between structure and properties.In this thesis, we first introduced the fabrication of organic ambipolar thin film transistors. Next, we successfully got high performance solution-processed OFET device based on TIPSPEN and tried to use solution method prepared organic single-crystal field-effect transistors. In addition, based on the ambipolar field-effect transistors building and testing method of the inverter are discussed ambipoalr field-effect transistors and CMOS inverter electrical properties and the relationship between them. Finally, monolayer and bilayer photosensitive field effect transistor were built and the photoresponse properties were tested, respectively.This thesis includes the following six parts:In chapter 1, an introduction was given on organic π-conjugate materials, along with the development situation. The basic knowledge of the field-effect transistor was introduced, including working principle, volt-ampere characteristic curve, charge transport model, the electrode and the gate dielectric function. We analyzed the two factors influencing the performance, π-conjugate system physical properties and the influence of the device. In addition, we introduced the type of organic small molecule materials.In chapter 2, in order to improve the performance of the thin film transistors, we optimized the organic semiconductor and two interfaces in the device. Though purification with tube furnace, changing substrate temperature in the process of evaporation, modified SiO2 with OTMS SAMs and introduction a buffer layer between semicondutor/electrode interface, we obtained better OTFT performance. This result provided an optimal way to test our new materials.In chapter 3, we prepared solution-processed organic field-effect transistors. We adopted drop methods successfully got high performance OFET device based on TIPSPEN, and then this method was adapted to our ambipolar materials. In addition, we optimized it to improve device performance. Furthermore, we tried to use sulotion method got organic single-crystal device, but the performance were lower than the OTFT devices, which need to optimize later.In chapter 4, we fabricated a series of CMOS and ambipolar inverters, and analysed the voltage transfer characteristic curve, gain and NM and other important parameters. We studied the working principle of CMOS and ambipolar inverters, explored the relationship between field-effect transistor carrier transport properties.In chapter 5, we constructed monolayer and bilayer organic photosensitive field effect transistors, respectively. A good photoresponse of red light was got from monolayer PhotOFET. In order to improve photoresponse the heterojunction structure was used, meanwhile, we found that the different bilayer devices showed different performance not only in OFET characteristics but also in photoresponse properties. In chapter 6, we summarized the results of this thesis. And we also analyzed the current the field-effect transistors institute face in the challenges and opportunities.