Synthesis And Properties Of Novel Phosphorescent Metal Complexes Based On Imidazole Derivative

Since organic molecules were first discovered could emit light in the 1930 s,this wonderful phenomenon has attracted the attention of researchers.With the continuous development of modern technology,the organic electroluminescent devices(OLED)have been developed.Compared with the traditional liquid crystal display(LCD)technology,OLEDs have been favored by various panel manufacturers because of their various advantages,Such as short response time,high contrast,no backlight,can achieve flexibility,curved surface,double-sided display and so on,thus becoming a leader in the field of display and lighting.According to the excited states of luminescent materials,they can be divided into fluorescent and phosphorescent materials,and most phosphor materials have chelating structures of heavy metal atoms.It has been found that the iridium complexes are widely used in the design of phosphorescent molecules,because of their advantages of high luminescence efficiency,short three-line radiation lifetime,good thermal stability and a wide range of emitting light.But iridium as a rare earth metal is relatively expensive,so copper can also be used as a cheap atom to make phosphorescent materials.Imidazole derivatives are widely used in the design of phosphorescent ligands as a good hole transport characteristic.In this paper,two novel benzimidazole and phenanthromidazole ligands were synthesized as the first ligand or auxiliary ligand to synthesize the corresponding iridium complexes and cuprous complexes.The optical,electrical and device properties of the complexes were determined.The main work is divided into the following three parts:Part ? two new neutral iridium complexes Ir(L)2(acac)and Ir(L)2(pic)have been synthesized by 1-(4-(9H-Carbazole-9-yl)phenyl)methyl-2-(4-(9H-carbazol-9-yl)-phenyl)-1Hbenzimidazole(L)as the first ligand and acac and pic as second ligands.The main emission peaks of the two complexes are located at 517 and 507 nm,respectively,and both emit bright green light.The thermal decomposition temperature is above 300 ?,indicating that the thermal stability is good.The devices of two kinds of materials were prepared by solution spin-coating method.The structure of the devices is ITO/PEDOT:PSS(40 nm)/CBP:Dopant(x wt%,40 nm)/TPBi(50 nm)/Liq(2 nm)/Al(150 nm).The results show that the maximum luminance of the two materials is 4914 and 3690 cd/m2,and the maximum external quantum efficiency(EQE)is 3.80 and 2.17%,respectively.Part ? two new ionic iridium complexes [(nbt)2Ir(1L)](PF6)and [(CF3-bt)2Ir(1L)](PF6)were synthesized by different dimer and 1-(4-(tert-butyl)phenyl)-2-(5-(9-(p-tolyl)-9Hcarbazol-3-yl)pyridin-2-yl)-1H-phenanthro[9,10-d]imidazole(1L)as the second ligand.The main emission peaks of the two complexes are located at 601 and 579 nm,respectively,which emit bright red light and orange red light.The thermal decomposition temperature is above300? and the thermal stability is good.The quantum yields of the two complexes are 5.51 and 1.72%,respectively.In order to evaluate the electrochemical properties of the two complexes,the multilayer devices of two kinds of materials were fabricated by solution spin-coating method.The structure of the devices is: ITO/PEDOT/PVK.PBD(10mg/ml):Dopant(x wt%)/TPBi/Liq/Al.the results show that,The maximum luminance of the two materials is 534.7 and 1021.0 cd/m2,and the maximum external quantum efficiency(EQE)is 1.48 and 1.40%,respectively.Part ? two cheap cuprous complexes [Cu(1L)(PPh3)2]BF4 and [Cu(1L)(DPEphos)]BF4were synthesized by using the previously synthesized ligand of phenanthroline imidazole(1L)and two kinds of diphosphine ligands triphenylphosphonate(PPh3)and bis(2-diphenylphosphorylphenyl)ether(DPEphos).The thermal decomposition temperatures of the two cuprous complexes were 262 and 405?,respectively,which indicated that the structures with ether oxygen bond had higher thermal stability.The main emission peaks of the two cuprous complexes are located at 472 and 498 nm,respectively.The main emission peaks of the complexes [Cu(1L)(DPEphos)]BF4 have a red shift of about 26 nm compared with[Cu(1L)(PPh3)2]BF4?This is because the conjugation degree of the [Cu(1L)(DPEphos)]BF4 is increased,and the non-localized ? electrons are more easily excited,thus the emission peak moves towards the direction of long wave.