Theoretical Study Of The Phosphorescence Properties For Transition Metal Ir(?) Complexes And Molecular Design Of Efficient Blue Materials

Due to the potential applications of phosphorescent organic light–emitting diode?PhOLED?in solid state lighting sources and color array display panels,PhOLED has attracted widespread attention.The key of studying PhOLED is to find the appropriate and efficient phosphorescent luminescent materials.As good phosphorescent materials,clear-cut color and high phosphorescent quantum efficiency(?_PL)are the necessary conditions.The strong spin–orbit coupling?SOC?of transition metal complexes can largely enhance phosphorescent quantum efficiency of materials.So,many researchers have concentrated on studying the third-row transition metal complexes.The cyclometalated Ir???complexes have been widely studied due to the high?_PL and short excited state life.The density functional theory?DFT?and time-dependent density functional theory?TDDFT?methods have been used to investigate the electronic structure,absorption and emission spectra,charge injection/transport ability and phosphorescence quantum efficiency.The main contents are as follow:1.Theoretical investigation on the effect of the modification of 2-phenylpyridine ligand on the photophysical properties for a series of iridium???complexes with carbazate ancillary ligands.We are hoping to explain the effect on the properties of luminescent materials by introducing-SO₂F group on ppy main ligands and different groups to increase the rigidity of the main ligands,and then provide valuable information for the design of high efficiency phosphorescent materials.Introducing electron-withdrawing group sulfuryl fluoride?–SO₂F?on benzene ring of ppy?2-phenylpyridine?ligands to increase the steric effect,the introduction of O,S atoms and C=C double bond increases the degree of conjugation and rigidity.Compared with experimental complex,the absorption/emission spectra of complexes which introduce O,S atoms are blueshifted.Complexes introduced O atom,C=C have better charge transporting ability.Complexes which introduce S atom,CH?CH₃?₂ may possess higher quantum efficiency and better hole and electron injection ability,and complex which introduces S atom could be the potentially efficient blue light materials.2.Theoretical investigation of the electronic structure and photophysical properties of a series of Ir???complexes bearing pentafluorosulfanyl groups.Introducing different ancillary ligands has a great influence on the FMOs,absorption spectra,?_PL and charge transport performance.Due to the larger effect of the strong electron-withdrawing property on the SF₅-ppy ligand in T₁ states,introducing different ancillary ligands has little influence on adjusting the emission spectra.Introducing different ancillary ligands has a major effect on the LUMO energy levels and energy gaps of the investigated complexes.The ptd ancillary ligand which is introduced thiazole on the thd ancillary ligand,the ntd ancillary ligand which is introduced nitrobenzene on the thd ancillary ligand could increase the intensity of absorption,?_S1,??_S1-T1,and then enhance the electron injection ability.The ntd ancillary ligand can decrease the LUMO energy level,energy gap,the electron and hole transport ability,and balance ability.The ptd ancillary ligand can disperse the electron density of the HOMO to the terminal groups on the ancillary ligand which enhances the contribution of the ancillary ligand,and could increase the electron and hole balance ability.The?_S1,??_S1-T1 are key factors in determining the quantum efficiency in the investigated systems.thd and tpip ancillary ligands could decrease??_S1-T1,increase?_S1 and thus enhance the phosphorescence quantum efficiency.All complexes in the investigated systems could be potential green-blue or green materials.