Fabrications And Studies Of High-performance Ambipolar Organic Field-effect Transistors And Inverters

Organic field-effect transistors (OFETs) have attracted much attention since the1980s. OFETs are not only essential building blocks for the next generation of cheap and flexible organic circuits, but also provide important insights into the charge transport behaviors of π-conjugated systems. Therefore, they may serve as strong tools to explore the structure-property relationships of π-conjugated systems, such as parameters of field-effect mobility, current on/off ratio, and threshold voltage.In this thesis, we firstly introduce the constructions and measurements of organic inverters based on complementary and ambipolar organic semiconductors, the electrical behavior of ambipolar transistors and inverters have being studied. Then we tried to modify the interfaces of OFETs to improve the device performance. Lastly, we made some explorations on solution-processed organic thin film transistors (OTFTs). And we also conducted some researches on the relationship between structures and device performance.The thesis includes the following contents:In chapter1, the history and development of organic semiconductors have been reviewed. Then we make a generalization of the classification for the organic semiconductors. OFETs based on organic semiconductors are introduced, including the device configurations, their working principles, and technologies for the device fabrication. We focus our discussions on the researches of OFETs based on ambipolar organic semiconductors, which could transport both holes and electrons.In chapter2, we fabricated a series of organic inverters based on ambipolar semiconductors. Their voltage transfers curves, gains and noise margins were tested. We gave a detailed discussion on the working principles of organic inverters and made a comparison of inverter performance and transistors behaviors.In chapter3, we used some high-performance semiconductor materials to serve as buffer layers between the source-drain electrodes and active layers. It is found that the performance of OFETs would be enhanced by the introduction of proper buffer layers.In chapter4, we made attempts to prepare organic semiconductor thin films by solution-process and use them in OFETs. We discussed the relationship between the preparation conditions and qualities of the thin films.In chapter5, we summarized the works in this thesis and made a brief plan for the next experiments. We also listed the main problems in the current studies of OFETs. We look forward to the practical applications of OFETs in the near future.