Organic Field-effect Transistors With Small Channel Length Based On Electrohydrodynamic Direct-writing Technology

Manufacture of organic thin film transistor(OTFT) array is the core of flexible electronics manufacturing, the channel length L is the key parameter that affects the performance of OTFT. Typically, the channel is fabricated by photolithography. The traditional method is complicated, highly cost, and its high-temperature process is not consistent with organic materials. Ink-jet printing provides another methods to make low-resolution channel. In this thesis, the gaps are defined by the electrohydrodynamic direct-writing(EHD) method, and then OTFTs are fabricated based on the above gaps. The main research work are introduced as follows:Firstly, the electrohydrodynamic direct-writing(EHD) under near-field conditions is studied. The effect of process parameters, including operation voltage, nozzle-to-substrate height and velocity of the substrate, on Taylor cone, flight behavior of jet and morphology of the deposited fibers is analyzed. With proper parameters, a large area of micro/nano-straight fiber pattern is printed out using the platform. Besides, the effect of the process parameters on the fiber width is characterized.Secondly, the transistor channel is fabricated using the electrospun fibers as sacrifice mask. Influence of magnetron sputtering process on fiber morphology is analyzed. The relationship between channel length and fiber width are studied. A large area of uniform channel with parallel or crossed pattern is realized.Thirdly, preparation and performance optimization of OTFT are achieved. Solution of preparing the transistor based on electrospun fibers is determined, including the material selection, structure design and preparation process. OTFT electrical performance is improved with a self-assembled molecular layer. Besides, influences of channel length, channel width, poly(3-hexylthiophene) annealing time and annealing temperature on OTFT electrical properties are researched. The optimized process parameters are realized to fabricate OTFT.In this thesis, electrohydrodynamic direct-writing provides a new digital manufacturing method of high-resolution channel patterns. Influences of process parameters on the fiber morphology and OTFT electrical performance are researched. The research work lays the foundation for the preparation of printing transistor array.