Using X-ray Diffraction To Study The Microstructure Of The Thin Film Of Poly Octyl Fluorene And Its Corresponding Optical And Electrical Properties

Organic polymer materials has opened an entirely new functional application of information materials and devices research and development areas in optoelectronic. Among a variety of organic polymeric materials, polyfluorene and its derivatives are regarded as the most promising commercial blue light emitting materials and widely studied because of its advantages such as wide bandgap, high luminescence efficiency. Current study on the polyfluorene and its derivatives are mainly focused in the development of new structure materials. However the relationship between the structure of materials, especially the aggregation state, and photophysical properties is still at an initial stage. There are still many problems in the industrialization of the polymer light-emitting materials. Studies have shown that these issues are directly related to the defect of conjugate polymers. Systematically study of the relationship between structure and properties of such materials will undoubtedly have great theoretical significance and practical value on the development and preparation of high-performance devices. Materials'aggregation state may be different from bulk materials due to space confine in films. This thesis will focus on the relationship between the morphology of polyoctylfluorene thin films and its electro-optical properties.At first, we briefly introduce the overview of polymer light-emitting materials and grazing incident X-ray diffraction (GIXRD). Second, we compared our material by characterize it using DSC, XRD and PL. Then we prove that spin-coated film is amorphous by using spectroscopy and X-ray diffraction methods. Atomic force microscopy results show that the film surface is smooth. The EL device was prepared and the results showed that the on-set voltage is 4V, and breakdown in 8V with the luminous intensity of 1668cd/m2. At last, the thermo-stable phase,α-phase, and the solvent vapor stable phaseβphase were studied. By using GIXRD, the background signal can be eliminated and diffraction signal of thin film can be enhanced. By varying the heating temperature it is found that the luminous efficiency is higher when the temperature is lower.βphase could be achieved by solvent vapor treatment or dipping method. The results show that shorter solvent vapor treatment will lead to higher luminescence, which is considered due to the smaller amount of defects. Comparing these films and their related devices with those of thin film achieved by dipping method, it could get smaller crystallites size and less defects, those will lead to higher luminescence efficiency and luminous intensity.