Synthesis And Applications In OLEDs Of Rigid Stereoscopic Platinum(?) And Palladium(?) Complexes

Organic light emitting diodes(OLEDs)are widely regarded as the next generation of efficient display and lighting technologies.Researchers have done a lot of research work to improve the brightness and luminous efficiency of the device.In order to reduce efficiency roll-off,optimization of device process and modification of molecular structure have been extensively investigated.A typical method is to weaken molecular aggregation caused quenching by introducing a steric hindrance group to decrease intermolecular packing.Another method is to construct multinuclear cyclometalated complexes,especially dinuclear platinum complexes.Dinuclear platinum complexes have attracted highly attention due to their advantages,such as a non-planar rigid structure,reduced?-?stacking,weakening concentration quenching.In this paper,a series of platinum(?)and palladium(?)complexes based on rigid steric hindrance have been synthesized.By introducing the rigid stereostructured pterene structure into the tetradentate ligand,the concentration quenching is suppressed and the photoelectric performance of the material is effectively improved.1.Synthesis and application of triptycene pyridazine symmetric tetradentate platinum(?)complex based on rigid steric hindrance.In this work,three symmetric tetradentate platinum(?)complexes with stereoterpene structure based on pyridazine are synthesized.The rigid stereostructure of triptycene structure was introduced into the tetradentate platinum(?)complexes based on pyridazine,which would not affect the coordination reaction,and the light color of the product would not change.Otherwise,it could enhance the steric hindrance and reduce the non radiative transition,thus preventing?-?stacking,which can ultimately improve efficiency.The photophysical properties of these three complexes were tested by the ultraviolet-visible absorption(UV-Vis),fluorescence spectra(PL)and cyclic voltammetry(CV).It was found that the introduction of isopropyl groups improved the luminescent properties.These three platinum complexes were substituted into the host material as small molecular guests to prepare high-efficiency orange phosphorus OLED devices.A maximum luminance of Pt-DPM,Pt-PIP and Pt-DPT were 26670 cd/m~2,29232 cd/m~2 and 57630 cd/m~2,and the maximum current efficiency is 23.67 cd/A,19.45 cd/A and 44.66 cd/A.The highest external quantum efficiency were 9.67%,9.93%,and 16.94%respectively.2.Synthesis and application of triptycene pyridazine symmetric octadental dinuclear platinum(?)complex based on rigid steric hindrance.In this work,two pyridazine-based ligands with stereoterpene structure have been synthesized,and symmetrical octadentate bisplatin(?)complexes are prepared by changing the coordination conditions.The photophysical properties of these three complexes were tested by the ultraviolet-visible absorption(UV-Vis),fluorescence spectra(PL)and cyclic voltammetry(CV).It is found that after the introduction of the second platinum(?)metal center,the maximum emission peak of the double platinum(?)complex 2Pt-TFP is red-shifted 44 nm compared to the single platinum(?)complex Pt-TFP.When applied to OLED devices,the maximum brightness of 2Pt-TFP and Pt-TFP are 11688 cd/m~2 and 23571 cd/m~2 respectively,the current efficiency is 12.63 cd/A and 18.16 cd/A,and the external quantum efficiency are 10.85%and 6.39%.3.Synthesis and properties of triptycene pyridazine symmetric tetradentate palladium(?)complex based on rigid steric hindrance.In this work,the tetradentate ligand designed in the previous chapter is used as the main ligand,and the cheaper palladium is selected as the metal center to coordinate with it.Two MADF materials—pyridazine-based symmetric tetradentate palladium(?)complex are obtained.The Pd-DDP and Pd-DPM compounds are studied by ultraviolet-visible absorption(UV-Vis)and fluorescence spectroscopy(PL)and cyclic voltammetry(CV)to study the luminescence properties of the complex.The palladium(?)complex Pd-DDP has been used to prepare an efficient green emitter.The maximum brightness of the OLED based on the pyridazine symmetric tetradentate palladium(?)complex Pd-DDP is 22658 cd/m~2,and the maximum external quantum efficiency and current efficiency are 15.34%and 50.43 cd/A.