Synthesis And Characterization Of Triphenylamine-Based Crossing Symmetric Small Molecules And Polymers

The structure, working principles of Organic Light-emitting Device (OLED) and research progress in light-emitting materials were summarized in this paper. In specially, the application of organic molecular emitting host materials in OLED were introduced in detail. The fluorescence quantum yield, carrier mobility, thermal stability and forming film properties are key to the efficience of OLED.Triphenylamine and its derivatives have high electron donating ability, hole transport properties and modification. Besides, triphenylamine and its derivatives are conjugated systems with excellent optical properties which can be applied in OLED.The following works were completed:1.(E)-1,2-bis(2-thienyl) ethylene was reported as a kind of high performance material in tuning spectral response region and energy level of frontier orbital. We have designed and synthesized (E)-1.2-bis(2-thienyl) ethylene modified TiO2as a photocatalyst. Methylene blue was used as a model material to examine the photocatalytic activities of (E)-1,2-bis(2-thienyl) ethylene/TiO2under visible (Vis) light. We found that the introducing of thienylenevinylene have expanded the spectral response region of TiO2to Vis light region, thus improving the photodegradation of TiO2under Vis light.2. Besides, we have designed and synthesized crossing symmetric small molecular based on triphenylamine.(1) We found that compound1-3are with crystalline nature and compound4-6are amorphous, and all of them are present excellent thermal stability through XRD, SEM, DSC and TGA.(2) Optical properties study:Compound1-6in dichloromethane exhibited similar absorptions with different absorption maxima between490nm-530nm and showed a significant red shift compared to triphenylamine (absorption maxima at300nm). Compound1-6exhibited green emission in dichloromethane with max emission wavelength in the region of490nm to530nm. All of these compounds exhibited a relatively high fluorescence quantum yield, short fluorescence lifetime and solvatochromism. The red shift of max absorption and emission wavelength in film compared with in dichloromethane was caused by molecular aggregation effect.(3) In CV experiment, we found that the introduction of side group can effectively tuned the energy level of frontier orbital of light emitting molecular which were further proved in theory calculation. The relatively high HOMO energy and the relatively low LUMO energy provided a narrow band gap which can improve the efficiency of OLED. In summary, compound1-6with excellent thermal stability, optical properties and electrochemistry properties can be applied in OLED as light emitting materials3. Based on previous work, we designed and synthesized branched phenyl-triphenylamine polymers P1-P3and thienylenevinylene-triphenylamine polymers P4.(1) We found that P1-P4are amorphous and all of them are present excellent thermal stability through XRD, SEM, DSC and TGA.(2) Optical properties study:P1-P4in dichloromethane exhibited different absorption and emission maxima in region of373nm to414nm and450nm to530nm, respectively. The molecular aggregation effect have caused the red shift of max absorption and emission wavelength in film compared with in dichloromethane. It is worth to point out that the emission of P4was different in film compared with in solvent. We presumed that the different molecular stacking of P4in film has caused the multiple emission. Besides, the relatively low fluorescence quantum yields were need to improve.(3) The CV experiment demonstrated that P1-P4were with high carrier mobility. In summary, the thermal, optical and electrochemical properties of P1-P4can satisfy the requirements of light emitting layer of OLED.