Effect Of Gel On Morphological Structure And Electro-optical Properties Of Polyoctylfluorene Thin Film

Conjugated polymer materials, which have excellent film making properties, processing properties, have developed a new research filed in photoelectric functional materials and devices field. Among the conjugated polymer materials, polyfluorene and its derivatives are generally regarded as the most promising materials of commercial application because of its wide gap, high luminous efficiency and it is found that polyfluorene have multiphase structure,which can be obtained a certain phase through selecting a proper treatment. The differences of microstructure are not only makeing material spectral change, but also affecting polymer photoelectric physical properties. However, in the experimental process,what often can be found is that the fluorescence spectra of film of solution do not always quite similar, after further treatment, fluorescent efficiency is also different.In this paper we detailed the solution preparation conditions and found the effect of gel on morphological structure and corresponding photoelectric properties.This paper briefly introduced the history and polymer electroluminescent materials, the research progress of our lab and basic situation of the gel of polythiophene and polyfluorene materials in the first chapter. The second chapter analyzed the effect of solution preparation condition on emission performance. We characterized the spin coating thin film made of polyoctylfluorene (PFO) in the toluene solution which be dissolved for 12 min,30 min and 90 min respectively under the 55℃by photoluminescene spectra, UV-visible sepctra and atomic force mcrioscope. The results indicate that the PFO thin film made of solution dissolving for shorter time con tains large gel particles with average size of 120nm×80nm, which lead to partlyβphase pho toluminescence. When dissolving time become longer, large particles disappear and the ph otoluminescence spectra was totally of amorphous phase. After solvent vapor treatment or thermo annealing the residual gel particle structure still remain, which decrease photolumin escence. These results indicate that the residual gel in the solution has negative effects on 1 uminous property of film. In the third chapter, we study the influence of ageing process on fluorene materials luminous performance. We keep the PFO solutions in the 20℃,25℃, 30℃biochemical incubator for several days. The results show that the longer the aging time,the larger the crystallites of PFO film, the more order the molecular chain arrangement.The analysis of atomic force microscope found that it is because with the aging time becoming longer,fluorene molecular chain can be fully extend and reach full and orderly state to generate aggregate, so as to make the film PFO molecular chain arrangement more orderly, reducing the defect formation and resulting in film photoluminescence properties enhancement. However, when aggregate size became big enough, on the contrary, it will affect the molecular chain arrangement, causing the regularity down and making fluorescence efficiency droping.