Study On Design, Synthesis And Characterization Of Fluorescent Molecules Based On Arylamine

Organic electroluminescent materials have attracted much attention in the research of optoelectronic information materials for the various advantages compared with inorganic light-emitting diodes. Materials based on arylamine are one of the most important materials for organic electroluminescent diodes (OLEDs). Molecules with triarylamine or N-arylcarbazole introduced in always show good hole-transporting ability. This dissertation focused on the synthesis of the bipolar D-Ï€-A types organic electroluminescent materials based on carbazole or triphenylamine (Donor) and quinoxaline, benzothiazole or imidazole (Acceptor) and their optoelectronic properties were studied in this paper. The main research work includes the following:Firstly, six D-Ï€-A molecules based on carbazole or triphenylamine(Donor) and quinoxaline (Acceptor) were designed and synthesized through Suzuki Coupling, their optical properties and emphatically the influence of molecular structure on optical performance was studied. Through a detailed study of their UV-visible absorption spectrums and fluorescence emission spectrums, we found that their UV absorption wavelengths were at 351-410 nm, and their fluorescence spectrums in CH2Cl2 emitted in the range of 494-500 nm and 554-560 nm respectively, representing blue-green light and pure green light. Electrochemical analysis of these compounds was carried out, and by using cyclic voltammetry, we calculated the HOMO orbital energy levels, and further obtained the LUMO energy levels. The results indicate that these compounds have a high thermal stability, high fluorescence quantum yield and suitable HOMO,LUMO energy level, which contribute to hole injection and electronic transmission, and they are potential bipolar multifunctional organic light-emitting materials.In the second part, luminescent materials of bipolar carbazole-benzothiazole type with hole injection and electronic transmission capabilities were synthesized. The absorption peaks at 345-393nm were characterized as the charge transfer from the carbazole molecule to benzothiazole molecule, as the UV absorption spectra showed. At the same time, we have studied the effect of conjugation degree,the number of donors and acceptors, and the introduction of styrene unit on luminescent properties of the materials, and we have obtained the optimizing structures of these compounds and their HOMO,LUMO energy level distribution through theoretical calculations. The results show that these compounds have a high glass transition temperature, high fluorescence quantum efficiency, good hole injection and electronic transmission functions, and thus they can provide support for future applications of organic light-emitting device.In the third part, luminescent materials of bipolar triphenylamine-benzothiazole type were synthesized. Influence of the number and location of benzothiazole on triphenylamine's skeleton and the introduction of styrene unit on luminescence properties of the materials were studied. Fluorescence emission peaks of the compounds were at 448-507 nm, representing blue-green light and pure green light. The results showed that emission peaks red shifted with the number of benzothiazole increasing; by increasing the styrene unit, pure (507 nm) green light-emitting materials were obtained and it provided reference for the structural design of light-emitting materials.In the fourth part, we designed and synthesized a series of fluorescent compounds of triphenylamine-imidazole type, and did a preliminary study on their spectrums and electrochemical properties. Their UV absorption wavelengths were at about 350-374 nm, and maximum fluorescence emission wavelengths were at 406-424 nm, for which they could be used as blue light-emitting materials. Electrochemical properties showed that the introduction of triphenylamine could effectively improve the redox properties of these compounds; HOMO energy levels were slightly higher than the commonly-used hole-transport material (NBP) (HOMO-5.20 eV, LUMO-2.40 eV), which is conducive to hole injection; LUMO energy levels were based on the number of donors in the molecules and were slightly lower than NBP,which is conducive to electronic transmission. It indicates that these compounds can be used as multifunctional doped light-emitting materials with light-emitting function,hole injection and electronic transmission functions.Finally, we designed and synthesized a series of hole-transport materials containing triphenylamine groups through Wittig-Horner reaction. We mainly studied the effect of molecular structure on optical performance by introducing double bonds,triple bonds and styrene units and by changing the length of conjugated molecules. It showed that emission peaks of these compounds were at 411-496nm, representing blue or blue-green light. Similarly, we tested luminescence properties of them in different solvents, we chose Toluene and DMF as solvents and measured their fluorescence spectrums, and we found that fluorescence emission peaks red shifted with the solvent polarity increasing. HOMO energy levels of these compounds are between-5.36- -5.71 eV and the corresponding LUMO energy levels are between-2.46- -2.93 eV, these compounds have a low band gap when comparing with other triphenylamine derivatives. And also their HOMO energy levels are very close to those commonly-used hole-transport materials.