Synthesis And Electroluminescence Of Iridium Complexes Based On Benzimidazole Ligands

Organic Light-Emitting Diode?OLED?are attracting more and more attention as emerging technologies in flat panel display and solid-state lighting.OLED technology is used by more and more electronic products.Phosphorescent materials play an important role in OLED,because they can simultaneously use singlet and triplet excitons for luminescence resulting in the theoretical quantum efficiency of 100%.Among them,benzimidazole-based iridium complexes have been paid more and more attention by researchers due to their high luminous efficiency,stable molecular structure,excellent electron transport performance and easy color adjustment.Based on the 2-phenylbenzimidazole ligand,the novel phosphorescent iridium complexes were synthesized by the modification of functional groups?-F,-CF₃,carbazole,diphenylphosphine oxide?dPPO??.The effects of different substituents on the photophysical properties and electroluminescent?EL?properties of iridium complexes were studied.The specific work is as follows:?1?A series of fluorine functionalized benzimidazole-based iridium complexes have been designed and synthesized?1F-Ir,2F-Ir,3F-Ir?.Their maximum emission wavelength is in range of 495-498 nm,and the photoluminescence efficiency varies from 0.68 to 0.81.Compared with the parent complex of 0F-Ir?520 nm,0.65?,the luminescent colorsblue-shift to about 20 nm,which is blue-green,and their luminous efficienciesare obviously improved.All these complexes have excellent EL properties,and 2F-Ir-doped OLED exhibites the maximum EL efficiencies of 21.7%,70.1 cdA^-1,24.2 lmW^-1,respectively.?2?Two novel bipolar iridium complexes?tpbi?2Ir?acac?and?cpbi?2Ir?acac?based on 2-phenylbenzimidazoles were designed and synthesized.The results show that the maximum emission wavelength of the two complexes is 520 nm,which is consistent with that of the parent complexes.Twobipolar complexes have high luminous efficiency of 0.61-0.72 and high thermal stability of 357-383 ??5% decomposition?.Doped devices based on?tpbi?2Ir?acac?have high efficiencies up to 60.6 cdA^-1 and 18.8 lmW^-1.?3?By introducing strong electron-withdrawing groups?-CF₃ and-dPPO?into 2-phenylbenzimidazole system,new iridium complexes pCF₃-Ir,mCF₃-Ir and po-Ir were designed and synthesized.The luminescence colors of pCF₃-Ir,mCF₃-Ir and po-Ir are obviously regulated due to the introduction of these substituents.Po-Ir has a red shift of 30 nm with respect to that of the parent complex,and the electrochemical results show that po-Ir significantly enhances the electron-transporting ability.The po-Ir-doped devices demonstrate high efficiencies of 75.3 cdA^-1 and 30.2 lmW^-1.