Synthesis Of Bipolar Organic Photoelectric Materials Based On Quinoxaline And Their Performances

Organic Light-Emitting Diode(OLED)has shown great application potential in solid-state lighting and full-color flat panel displays due to their self-luminescence,high brightness,high color contrast and other advantages,which has attracted great attention from the research community and the industry.In order to obtain OLED devices with excellent performances,the preparation of luminescent materials is of great importance.Among them,fluorescent materials have become a hot spot for researchers in recent years due to their advantages of low cost of preparation and excellent stability.Therefore,it is necessary to develop fluorescent materials with excellent performance.In this paper,a series of quinoxaline bipolar materials,in which quinoxaline and carbazole groups were used as the electron acceptor and the electron donor,respectively,were designed and synthesized,and their photophysical properties,electroluminescence performances had been systematically explored.The specific work was as follows:(1)Using benzil compounds as raw materials,by adjusting the ratio between the electron donor and electron acceptor groups and the mutual positional relationship between them,five new small molecule fluorescent materials 2,3-DB-6-CZQx,2,3-DB-6,7-DCZQx,2,3-DBCZQx,2,3-DBCZ-6-CZQx and 2,3-DBCZ-6,7-DCZQx were designed and synthesized.Studies have shown that the maximum emission wavelengths of 2,3-DB-6,7-DCZQx and 2,3-DBCZ-6,7-DCZQx were 522 nm and530 nm,respectively,which were nearly 30 nm red-shifted compared to the other three compounds.Blue OLED devices were prepared with 2,3-DB-6,7-DCZQx and2,3-DBCZ-6,7-DCZQx.Among them,the device based on 2,3-DB-6,7-DCZQx showed better performance,and the maximum efficiencies obtained were: 2.88%,3.6lm/W and 7.4 cd/A.(2)In order to improve the rigidity and conjugation degree of compounds,two new small molecule fluorescent materials 11,12-DCZDBPN and 3,6-DCZDBPN were designed and synthesized by using phenanthrenequinone structure.Studies have shown that the maximum emission wavelengths of compounds 11,12-DCZDBPN and3,6-DCZDBPN were 562 nm and 532 nm,respectively.And by comparing the two compounds with similar structures to the forementioned,it was founded that the maximum emission wavelengths of compounds 11,12-DCZDBPN and 3,6-DCZDBPN had a significant red shift.Green and blue OLED devices were prepared with 11,12-DCZDBPN and 3,6-DCZDBPN.Among them,11,12-DCZDBPN-based devices showed better performance,with a maximum efficiency of 1.72%,2.41 lm/W and 4.9 cd /A.(3)In order to improve the electron-transporting performance,a novel small molecule fluorescent material 11,12-DCZDPPN was designed and synthesized by using 1,10-phenanthroline-5,6-dione as the raw material.The study found that,compared with compound 11,12-DCZDBPN,the introduction of N atoms on the benzene ring can effectively increase the thermal stability of the compound.In addition,the introduction of N atoms reduced the LUMO energy level of this material,which was more conducive to the injection of electrons,thereby improving the electroluminescence performance of the compound to a certain extent.The maximum efficiencies obtained by the green OLED device prepared based on 11,12-DCZDPPN was: 1.9%,2.6 lm/W and 6.2 cd/A.