The Study Of Fabrication And Property Of The N-type Organic Thin Film Transistors

Organic thin film transistors (OTFTs) are widely applied in the fields of smart cards, electronic radio frequency cards, sensors, commodity labels, and so on. In recent years, the development of OTFTs has reached commercial application level, and OTFTs also show a great potential application due to there facile fabrication at room temperature, low cost and superior performance.In this thesis, OTFTs were fabricated using PTCDI-8 (N,N'-dioctyl-Perylene- 3,4,9,10-tetracarboxylic acid diimide), and their properties were characterized. The main contents and results are summarized as follows:Firstly, the effects of different types of insulation materials on the performance of OTFTs were studied. Two types of OTFTs were fabricated using two types of insulating layers respectively, such as SiO₂, polymethylmethacrylate (PMMA)/SiO₂. The OTFTs with different insulating layers were fabricated via the self-made vacuum evaporator. The properties of two kinds of insulating layers were tested by KEITHL EY 4200, kelvin probe instrument. The structures of these two insulating layers were characterized by atomic force microscopey (AFM) and x-ray diffractometer (XRD). The ideal metal electrode of OTFTs can be achieved by testing the work funtion of OTFTs. It also can be found that the electric properties of devices with PMMA/SiO₂ insulating layer are better than those of devices with SiO₂ insulating layer because the surface roughness of PMMA/SiO₂ layer is less than that of SiO₂ layer. The semiconductor PTCDI-8 can be well crytallized and orderd on the surface of the PMMA/SiO₂ layer, which are favorable for increasing the electronic mobility.Secondly, the effect of self-assemble silane monolayer on the properties of OTFTs was studied. We choseγ-APTES and n-PETS as two kinds of self-assembled materials, which were self-assembled on the surface of SiO₂ as a modified layer between SiO₂ insulating and semiconductor layers. The results show that the self-assembled polar films play an active role in promoting carrier mobility and the on-off current ratio, as well as reducing the threshold voltage for OTFTs, which indicate that the organic/inorganic hybrid monolayer could improve the surface performance of SiO₂ insulating layer and the quality of organic semiconductor films via effectively reducing the surface mismatch between the inorganic insulator (SiO₂) and organic semiconductor films (PTCDI-C8). Furthermore, the results of the modified layer prepared by the polar molecular self-assemble layer indicate that the density of the charge carriers on the surface of the organic semiconductor film layer can be ajusted by designing the molecular extremity.