Study On The Influence Of Different Main Ligands On The Phosphorescence Properties Of Ir(Ⅲ) Metal Complexes

Because the cyclometalated iridium（Ⅲ）complex can easily adjust its emission color from pure blue to near-infrared,and the excited state life is relatively short,the efficiency is high,and it has good thermal stability.It is considered to be a material for the light-emitting layer of OLEDs with good performance.In this paper,the geometric,electronic and photophysical properties of iridium（Ⅲ）complexes are studied by using density functional theory and time-dependent density functional theory.（1）The property changes of the two series of iridium complexes caused by changing theπ-conjugation length are comparatively studied.The calculated geometric parameters of the complexes are in good agreement with the available experimental values,which shows the reliability of the calculation method used.In addition,comparing the properties of the two series of complexes,it is found that the cyclometallic iridium complex with a meta-naphthalene structure has the smallestΔE_L-Hlevel.And the lowest emission wavelength shows a significant red shift.The calculation results show that extending theπ-conjugation of the main ligand can adjust the emission of the iridium complex and has an important influence on the photophysical properties.（2）The geometric structure,electronic structure and photophysical properties of a series of mixed carbene cyclometallated iridium（Ⅲ）complexes with different auxiliary ligands have been studied.In the CH₂Cl₂medium,M062X is used for simulation calculation,and it is found that the lowest energy emission wavelength is between 399-498nm.A composite designed may have the largest radiation attenuation rate（k_r）value and may be a potential candidate for blue emitters in organic light-emitting diodes.（3）A second cyclometalated ligand was introduced,and the electronic structure and photophysical properties of five iridium（Ⅲ）complexes were compared.These complexes have a twisted octahedral configuration around the Ir center.The introduction of different second cyclometalated ligands has different degrees of influence on the HOMO orbital of the complex,and its emission wavelength varies between 558-658 nm.This indicates that the introduction of the second cyclometalated ligand is also an effective method to adjust the color of the iridium complex.At the same time,the introduction of-B（Mes）₂at the pyridine end showed a higher radiation decay rate than the complex introduced at the phenyl end.