Synthesis And Electroluminescence Properties Of Red Phosphorescent Iridium Complex Based On Phenyquinazoline Ligands

Organic light-emitting diodes(OLEDs)have many advantages,such as high brightness,high efficiency,full-color display,wide viewing angle,low driving voltage,fast response,easy preparation,flexible display,etc.,which have attracted great attention of researchers,and have been gradually commercialized in solid-state display and lighting fields.Compared with fluorescent materials,phosphorescent metal complexes can utilize both singlet excitons and triplet excitons due to the spin-orbit coupling effect of heavy metals,so that the internal quantum efficiency can reach 100%theoretically.Among these phosphorescent materials,iridium complex is a strong candidate because it is easy to modify and the photophysical properties can be reconciled with good stability.In this paper,several new iridium complexes were designed and synthesized by modifying the main ligand and coordinating with different auxiliary ligands.The HOMO and LUMO of the target complex were calculated by theoretical calculation and photophysical properties test.Based on this data,a suitable phosphorescent host material was found,and a dopant phosphorescent OLED device was fabricated and its electroluminescence properties were tested.The specific work contents are as follows:(1)Five pure red iridium complexes(Ir1-Ir5)were synthesized by the introduction of tert-butyl(t-Bu)and diphenylamine(NPh₂)at the 4-position of the 6,7-dimethoxy quinazoline benzene ring with the coordination of auxiliary ligand acetylacetone(acac)and picolinic acid(pic).The effects of different electron-donating groups and auxiliary ligands on the luminescence properties of the complexes were studied.Taking complex Ir4 as an example,it was doped in different host materials CBP and 2,6-DCz PPy,and the influence of host materials on device performance was explored.The results show that the device based on2,6-DCz PPy host material has better performance.In addition,we also optimized the doping concentration of the complex in the 2,6-DCz PPy host material.The device based on 10 wt%complex Ir4 has the best performance.Its electroluminescence wavelength,maximum luminance,current efficiency,and external quantum efficiency are 620 nm,22455 cd m^-2,32.17 cd A^-1,26.22%,respectively.(2)Three iridium complexes(Ir6-Ir8)were synthesized by introducing methoxy in the 3or 4 position of 6,7-dimethoxy quinazoline benzene ring with the coordination of auxiliary ligands acac and pic.The effects of substituent positions and auxiliary ligands on the luminescence properties of the complexes were studied.In dichloromethane solution,they exhibit orange,near infrared and infrared emission at wavelengths of 570,667 and 694 nm,respectively.Compared with complex Ir1,complex Ir6 has a blue shift of 29nm,while complex Ir7 and Ir8 have a red shift of 67 nm and 94nm,respectively.The results show that the substituted position of methoxy group and the difference of auxiliary ligand have a significant effect on the luminescence wavelength of the complexes.