Synthesis Of Benzoindole Modified Carbazole Derivatives And Study Their Properties

The organic light emitting diode(OLED) has attracted a substantial amount of interest of many researchers in the recent decades due to its practical applications in solid state lighting and flat panel display. OLEDs have the incomparable advantages of other devices, however, there are few commercial OLEDs, mainly due to the lifetime and efficiency of red and green lights in RGB three primary colors of OLEDs are higer than those of blue OLEDs. Therefore, improvement of efficiency and lifetime of blue OLEDs will greatly contribute to the early realization of the industrialization of OLEDs. At present,the commonly used method to improve the lifetime and efficiency of OLEDs is the optimization of the device structures and the reasonable selection of the materials, among which, rational design of light emitting layer materials plays a very important role in the improvement of the lifetime and efficiency of OLED device. Bipolar materials possessing D-A system are widely used as ideal host materials in light emitting layer of electroluminescent device, mainly because such material has good carrier transportproperties for a balanced recombination of holes and electrons, and can simplify the OLED device structure, expand the exciton formation region, as well as reducing the efficiency of the mutation.Therefore, it has great significance for the study of the materials featuring such structural characteristics.This paper is mainly based on the research on the design, synthesis and performance of bipolar host material with new structures, and the research content is divided into the following sections:(1) The five novel bipolar host materials were designed and synthesized through the multi-component solvent-free melt condensation method and Suzuki coupling method, using two kinds of hole transport groups of carbazole and benzo-indole as electron donors, cyanide and pyridine groups with strong electron affinity ability as electron acceptors. The structures of the complexes were characterized by matrix assisted laser desorption ionization time of flight mass, GC-MS and NMR, etc.(2) The five compounds(CzPyBI-2,CzPyBI-3,Cz CNPyBI-1 and Cz CNPyBI-2) exhibit good solubility,which can be made into OLED device by wet spin process.(3) Studies on the properties of the electrochemical, photophysical, thermal stability, and the molecular simulation showed that these five bipolar host materials exhibit good light emitting performance in the pure blue region with a high glass transition temperature(T_g > 100 °C) and high thermal decomposition temperature(T_d > 390 °C). Molecular simulation indicates that different distribution of the HOMO energy level will make the OLED devices exhibit different performance.