Design,Synthesis And Potoelectric Properties Of Phosphorescent Materials Based On Tetradentate Platinum (?) Complexes

As the display and lighting technology becomes more and more important today,OLED,as a new generation of display lighting materials,has attracted a large number of scientists to study it tirelessly because of its great potential for practical application.The development of light-emitting materials is crucial to the development of OLED.Tetra-dentate platinum(?)complexes have strong structural rigidity,and the coordination center is planar quadrilateral configuration.On the one hand,the strong structural rigidity can suppress the distortion and vibration of molecules to the greatest extent,reduce the non-radiative transition rate of molecules,and improve the luminescence performance;On the other hand,too planarization coordination configurations can easily cause aggregation quenching between molecules and reduce luminescence efficiency.In order to make full use of the advantages of structural rigidity of tetrodentate platinum(?)complex and reduce the efficiency reduction caused by molecular aggregation,the main content of this thesis is to design and synthesize phosphorescent materials based on tetrodentate platinum(?)complex.The research contents are as follows:(1)The O^N^C^N-type tetradentate platinum(?)complex TPt A and its terminal phenyl functional group fluorinated derivative TPt B were designed and synthesized.By introducing N-phenylcarbazole as a large steric hindrance group,the intermolecular interaction can be reduced,and the aggregation quenching of intermolecules can be reduced.The photoluminescence quantum yield(PLQY)of TPt B is 0.86,which is much higher than 0.54 of TPt A.Contrary to the PLQY results,the device performance of TPt A is better,because the terminal group of TPt A has a certain steric hindrance,which keeps the device efficiency better at both low and high concentrations.On the other hand,TPt B exhibits poor device performance due to the less steric hindrance of the terminal group and possibly because the fluorine atom will strengthen the interaction between the complex and other molecules.The higher the doping concentration,the more obvious the degradation of device performance.(2)The Schiff base-type platinum(?)complexes SPt A and SPt B were designed and synthesized by introducing large sterically hindered phenyl groups at the periphery.According to the optimized structure calculated by Density Functional Theory(DFT),it can be concluded that the peripheral phenyl groups of the luminescent centers of SPt A and SPt B molecules play a role in hindering molecular aggregation,which is effectively reduced because the intermolecular distance is too large.Aggregation quenching due to proximity.The photoluminescence quantum yields of SPt A and SPt B are 0.45 and 0.47,respectively,which are higher than the reference molecules without the introduction of sterically hindered phenyl groups at the periphery.By optimizing the structure of the light-emitting layer,the optimal device was obtained by using TCTA and Tm Ty PB as mixed hosts,the thickness of the lightemitting layer was 30 nm,and the doping concentration of SPt B was 3 wt%.Its maximum current efficiency(CE),power efficiency(PE)and external quantum efficiency(EQE)are10.5 cd/A,7.2 Im/W and 9.6%,respectively.The device has a maximum emission wavelength of 630 nm and CIE coordinates of(0.64,0.35),which is a red phosphorescent OLED device with high color purity.