Study On The Micro-region Structure And Properties Of Dithienothiophenes-dicarboxylic Acid

Thiophene derivatives have been received increasing attention because it is easy to process,chemically stable.The interest in thiophene derivatives has spread from early dye chemistry to modern drug design,electronic and optoelectronic devices, biodiagnostics,self-assembled,and conductivity-based sensory devices.In these compounds,dithienothiophenes are rich in sulfur,with three S atom,they are electron rich species,which makes them good electron donors and important building blocks of a wide variety of materials for optical and electronic applications.The results have shown that organic optoelectronic devices performance not only the chemical structure of individual molecule but also rely on self-organization structure of all molecules on substrate.Therefore,people studied the relation between its micro-region structure and properties of dithienothiophene derivatives.These results provided an important experimental data and valuable new ideas to use these organic materials to fabricate high-performance organic optoelectronic devices and organic field effect transistors.There are three main parts in this thesis:Part one:The atomic force microscopy(AFM) study of film forming properties of dithienothiophenes-dicarboxylic acidBy evaporation of the solvent method on the substrate to construct self—organized films of dithieno[3,2-b;2',3'-d]thiophene-2,5-dicarboxylic acid and dithieno [2,3-b:3',2'-d]thiophene-2,5-dicarboxylic acid,AFM was used to study the film forming properties.Through explorating the conditions of film forming dithienothiophenes-dicarboxylic acid film,some experimental data should be provided for preparing the ideal film structure.Part two:Study of the micro-region structure and properties of two dithienothiophenes-dicarboxylic acid.Self-organized of dithieno[3,2-b;2',3'-d]thiophene-2,5-dicarboxylic acid and dithieno[2,3-b:3',2'-d]thiophene-2,5-dicarboxylic acid films were prepared by evaporation of the solvent method.The microstructure of two compound films were observed by AFM,which demonstrated that the dithieno[3,2-b;2',3'-d]thiophene-2,5- dicarboxylic acid was a certain angle oriented arranged on the mica substrate,and the monolayer of dithieno[2,3-b:3',2'-d]thiophene-2,5-dicarboxylic acid was lying on the mica substrate.The optical and conductance properties in tiny region of these two compound films were characterized by UV-vis absorption spectroscopy,fluorescence spectroscopy and conductive atomic force microscopy(C-AFM).The results revealed that the fluorescence peak and absorption peak of dithieno[3,2-b;2',3'-d]thiophene-2,5 -dicarboxylic acid have a large red shift with compare to dithieno[2,3-b:3',2'-d] thiophene-2,5-dicarboxylic acid,and the conductance of the J-aggregates formed by dithieno[3,2-b;2',3'-d]thiophene-2,5-dicarboxylic acid on the substrate was three orders magnitudes higher than that of the dithieno[2,3-b:3',2'-d]thiophene-2,5-dicarboxylic acid.The large conductance difference mainly comes from the different aggregation structure and orientation of these two molecules on substrate.Part three:Study of the micro-region structure and properties of dithieno[3,2-b;2',3'-d]thiophene-2-dicarboxylic acidSelf-organized of dithieno[3,2-b;2',3'-d]thiophene-2-dicarboxylic acid films were prepared by evaporation of the solvent methods.Film forming and photoelectron transport performance of the films were studied atomic force microscope,UV-vis absorption spectroscopy,fluorescence spectroscopy and C-AFM.The results revealed that the compound have good film-forming performance.Due to the strong inter-molecular interactions,molecules are prone to close aggregate film in the process of film-forming.Because molecules are easy to form the close aggregate,enables it to have the high electron transport performance.