Design,Synthesis And Photoelectric Properties Of Carbazole-Oxadiazole-Based Small Molecules And Their Iridium Complexes

Organic electroluminescent diodes(OLEDs),as the mainstream display materials on the market,have aroused extensive attention and research interest of scientific researchers.Phosphorescent transition metal complexes are one of the most important luminescent materials in the preparation of OLED devices.In this paper,We chose the carbazole-oxadiazole group to synthesize a series of cyclic metal C^N iridium complexes.and realized the regulation of the luminescence properties of the complexes through the modification of the ligands.In addition,three carbazole-oxadiazole-based small-molecule host materials were designed and the performance of the series of materials was explored.At the same time,we introduced electron donating and electron withdrawing groups in the ligand structure to further modify,and explore the influence of the introduction of different groups on the performance of the device.The specific research content of this paper is as follows:(1)Four iridium complexes based on carbazole-oxadiazole as ligands were designed and fabricated into OLED devices.Through related characterization,research and analysis of their photophysical and electrochemical properties and the optoelectronic properties of the devices,the result shows,the luminescence spectrum of the iridium complex is in the range of yellow-orange light(517-530 nm),the emission spectra of Ir-M-M and Ir-M-F(2,6)are significantly larger than those of Ir-B-M and Ir-B-F(2,6),indicating that the electron-donating group contributes to the improvement of the LUMO energy level of the complex.Thereby increasing the energy gap of HOMO-LUMO,leading to a red shift of the emission spectrum.It can also be seen from the cyclic voltammetry graph of the iridium complex that the electron donating group helps to increase the LOMO energy level of the complex,thereby increasing the complex The energy gap of the complex redshifts the spectrum of the complex.In addition,the current efficiency of Ir-MF(2,6)reached 18.1cd/A-1,and the luminous brightness reached 11856 cd/m2,indicating that the electron withdrawing group on the 5-position of oxadiazole makes the energy between the host and guest materials The transmission is stable and the efficiency is high,which is conducive to the improvement of the device performance.(2)Carbazole and 1,3,4-oxadiazole groups are cleverly introduced into the same molecular structure as hole-transporting groups and electron-transporting groups,three host materials were designed and synthesized and fabricated into OLED devices.The photophysical and electrochemical properties of these three bipolar host materials and the photoelectric properties of the devices were studied.The results show that the luminescence spectra of the synthesized bipolar materials B-M3,B-Cz2,and B-DPA iridium complexes are in the range of yellow-orange light(428-562 nm),with the introduction of diphenylamino and dicarbazole phenyl Compared with trimethylphenyl,the red shift is more obvious.The material has good solubility in most solvents and can be used in OLED devices prepared by dry evaporation.Among them,the test data of B-Cz2 devices is the best.The brightness of the manufactured devices is up to 10325 cd/m2,and the current efficiency is It reached 13.2 cd/A-1,indicating that the stronger the electron-withdrawing group introduced into the 5-position of oxadiazole,the more significant the performance improvement of the prepared device.