Synthesis And Photoelectric Properties Of Phenylquinoline Iridium Complexes

The OLED industry is in a period of rapid development.In 2016,the national 13 th Five-Year Key R&D plan made OLED one of the key projects.The full name of OLED is organic light-emitting diode,also known as organic electro-laser display,organic light-emitting semiconductor.Flexible OLED is the basis for realizing curved display and even future flexible display.At present,the development of the OLED industry has attracted attention at the national level and is strongly supported by the country.The industry is in a period of rapid development.Because the iridium complex has a relatively short triplet lifetime and high luminous efficiency,it has become the most studied OLED phosphorescent light-emitting material.In view of this,this paper designed and synthesized two red iridium complexes Ir-1 and Ir-2.A red light iridium complex Ir-1 was synthesized,with2-(3,5-dimethylphenyl)-7-methylquinoline as the main ligand and 3,7-dimethyl-5-methyl-4,6dione as the auxiliary.A red light iridium complex Ir-2 was synthesized,with 2-(3,5-dimethylphenyl)-7-methylquinoline as the main ligand and3,7-diethyl-3,7-dimethyl-4,6-dione as the auxiliary.The structures of the two compounds were identified by 1H NMR and LC-MS,and their photophysical,electrochemical and thermal stability properties were studied in detail.After high-temperature vacuum sublimation and HPLC inspection of purity,devices with Ir-1 or Ir-2 as the light-emitting layer were successfully prepared,and both devices showed good device performance.The starting voltage of the device with Ir-1 as the light-emitting layer is 3V,the maximum current efficiency CEmax is 21.7cd/A,the maximum power efficiency is 22.71lm/w,the maximum external quantum efficiency is 17.82%,and the lifetime of the device is attenuated to 95%.For 70 h.the starting voltage of the device with Ir-2 as the light-emitting layer is 2.75 V,the maximum current efficiency CEmax is 25cd/A,the maximum power efficiency is 26.17 lm/w,the maximum external quantum efficiency is 18.37%,and the device lifetime is 85 h when the device life is attenuated to 95%.Using density functional method(DFT)and time-dependent density functional method(TD-DFT)to systematically study the geometric structure,energy,and frontier molecular orbitals of ground state,first excited state and lowest triplet geometric structure for complexes Ir-1 and Ir-2.For the complex Ir-2,the introduction of the electron-donating group methyl on the co-ligand increases the HOMO-LUMO energy gap of the ground state and the excited state.The difference in energy gap between the first excited state and the lowest triplet state of complex Ir-2 is smaller than that of complex Ir-1,which is more conducive to the occurrence of intersystem crossing and is conducive to improving the luminous efficiency of phosphorescence.It is proposed that reducing the energy gap difference between the first excited state and the lowest triplet state can better improve the phosphorescence efficiency of the complex.The theoretical calculation results studied in this paper are helpful to the adjustment of the photophysical properties of Ir(III)complexes and the design of high-performance molecules.