Research On Fabrication And Performance Of Thin Film Transistors Based On Vanadyl-Phthalocyanine

In the field of display,organic thin film transistor has become the core of the latest flexible display technology.How to reduce the threshold voltage of the organic film body and improve the stability of the device has become an important research topic.This paper focuses on mainly on how to reduce oxygen phthalocyanine vanadium?VOPc?organic thin film transistor threshold voltage,the vanadium?VOPc?phthalocyanine oxygen as organic thin film material of synthesis of tubing,exist,such as organic semiconductor materials of the poor thin film crystalline,decorated with different materials as an organic thin film transistor layer and choose BP2T molecules as heterogeneous epitaxial layer material as interface modification,and compared the change of the interface morphology.The morphology and crystallization of organic semiconductor films were improved to reduce the threshold voltage.The effects of different interface modifications on the I-V characteristics of the device were compared and analyzed by measuring vanadium phthalocyanine thin films by atomic force microscope?AFM?and X-ray diffraction?XRD?.These conclusions are beneficial to the growth of organic semiconductor thin films and the improvement of the performance of organic thin film transistors.The thesis mainly includes the following two aspects:?1?Study the influence of interface modification OTS on the film morphology and device performance:the VOPc grown directly on the insulation layer and the VOPc grown after OTS-18 modification.All OTFTs used heavily doped n-type silicon wafers with SiO₂ insulation layer as the substrate,and the structures of the prepared devices were all bottom gate top contact structure devices.Atomic force microscope?AFM?characterization tests were conducted on the two groups of prepared VOPc films.The interfacial modified VOPc film and the unmodified VOPc film were tested and analyzed to study the effect of interfacial modification on the morphology and growth of VOPc film.The experimental results show that the VOPc film can form more continuous crystal form after modification with OTS-18,the morphology of VOPc is more smooth,the crystal is larger,and the intercrystalline boundary is reduced.The OFET transfer characteristic curves of each group of devices were tested and analyzed respectively,and it was found that the device after OTS-18 modification was more conducive to the generation and transmission of carriers,and the threshold voltage was significantly reduced,which could effectively improve the performance of the device.?2?To research the effect of heteroepitaxial layer on the film morphology and device performance:Vanadium phthalocyanine?VOPc?is used as the material of organic semiconductor layer after secondary purification.BP2T small molecules are deposited on the surface of insulating layer by vacuum deposition technology respectively to form BP2T films with thickness of 2nm,2.5nm and 3nm.And it continues to deposit 20nm VOPc thin film on the surface of BP2T thin film.BP2T modified layer and VOPc predestined layer form a modified layer structure with homogeneous junction.The morphology of the modified layer structure is compared with that of single layer VOPC thin film.Through this comparison,we can know that the modified layer of BP2T can improve the morphology of VOPc films grown on BP2T.After the VOPc induced on BP2T,we can see that the morphology of VOPc on BP2T is smoother,the crystal is larger and the crystal boundary is reduced.The surface VOPc morphology of the films modified by BP2T 3nm is the smoothest,the crystal is the largest and the crystal boundary is the smallest.The OFET transfer characteristic curves of each group of devices are tested and analyzed respectively.It is found that when the modified layer is BP2T2.5nm and 3nm,it is most conducive to the generation and transmission of carriers,and the threshold voltage is the lowest.It is concluded that when BP2T is covered with one layer,the performance of the device can be improved and the threshold voltage can be reduced.The reason is that the interface modification can effectively increase the crystal size and then reduce the traps in the film.