Theoretical Study Of Probing The Effect Of Substituent Groups In Ir(Ⅲ)bis-tridentate Complexes During Highly Efficient Deep-blue Phosphorescent

With the organic light-emitting diode(OLED)becoming more and more mature,its application range is more and more extensive from equipment manufacturing to panel manufacturing to VR,wearable equipment and other fields,which is gradually realizing commercialization and has a rapid growth trend.In recent years,as the second generation of organic light-emitting materials,phosphorescent organic light-emitting diodes(PHOLED)have attracted much attention,because it can achieve nearly 100% of the quantum efficiency of light-emitting.Most of the phosphorescent organic light-emitting diodes(PHOLED)materials are transition metal complexes,especially those iridium complexes.These complexes have chemical stability and color emission compatibility.In the process of phosphorescence illuminating,the iridium complexes can produce the pure blue spectrum of visible region due to center Ir(III)atom induced the transition process between single excited state with triple excited states.Iridium transition metal complexes can form a stable octahedral structure,Which can affect thephotophysical properties of the complexes by the coordination of auxiliary ligands or substituents on the basis of stable chemical structure.The emitting wavelength and efficiency of a series of blue phosphorescent bis-tridentate iridium complexes have been evaluated quantitatively using comprehensive theoretical approaches.In this research,we use density functional theory(DFT)and time-dependent density functional theory(TDDFT)to investigate the geometries,electronic structures,radiative decay processes,non-radiative decay processes and intersystem crossing processes of a series of bis-tridentate iridium transition metal complexes.We further calculate the radiative decay rate by using the spin-orbit coupling theory,and analyze the main influence factors of radiative decay rate in detail.We calculate the non-radiative decay rate constants of different ligands and substituents according to the energy gap law method..We not only analyze the factors that affect the quantum efficiency of phosphorescence,but make a reasonable prediction.Among these complexes,Skyblue and 1-4 have been synthesized in the laboratory.We designed the complex 5 which can emit blue phosphorescence efficiently.According to the theoretical calculation results,the slightly blue shift in the emission of complex 1-4 is attributed to the ether link between two aromatic groups.On the one hand,introducing ether link leads to the decrease of transition dipole moments,which consequently decreases kr.On the other hand,comparing with the strong electron attracting group CF3,kr can be enlarged by the electron donating group But.Further analysis of vibrational modes indicates that a higher reorganization energy at low frequency region occurs easily a faster non-radiative decay process.These results show that the quantum efficiency can be effectively improved by using a reasonable non-conjugated tridentate ligand and electron donor group.We sincerely hope that the whole theoretical analysis method in this study can be helpful for the analysis of experimental synthesized molecules.