Design And Synthesis Of Phenanthroimidazole Small Molecule Luminescent Material And Their Application In OLEDs

Organic light-emitting diodes(OLED)have many advantages,such as ultra-thin,flexible,bright color,light weight and low energy consumption,which have a wide range of applications in flat panel display and solid state lighting.Luminescent materials are the core part of OLED,while blue light materials,as one of the three primary color materials,are extremely challenging in molecular design and synthesis due to their high energy gap and low carrier injection and transmission performance,which seriously restricts the industrial development of OLED.In recent years,phenanthroimidazole units have attracted great attention as they play an important role in the construction of effective deep blue luminescent materials.Phenanthroimidazole unit has high luminescence efficiency,excellent thermal stability and relatively balanced carrier injection and transport capability,simple synthesis and easy to modify.In this paper,by the introduction of hole-transporting aromatic amines and large steric structural groups in the N-1 of phenanthroimidazole,a series of new bipolar phenanthroimidazole blue light compounds were designed and synthesized,and their photophysical properties,electrochemical properties and thermodynamic properties were investigated.The non-doped devices based those compouds were prepared and their electroluminescence performances were sdutied.The specific work is as follows:(1)Three novel bisphenylbenzimidazole compounds,NN-BPI,NN-PPI and DN-PPI,were designed and synthesized by introducing the hole-transporting aromatic amines into the N-1 of phenanthroimidazole.The effects of N-1 phenanthroimidazole binding arylamine on the photophysical properties of the compounds were investigated.The three compounds all exhibited different degrees of blue emission in solution,and all had high thermal decomposition temperature.The introduction of carbazole group in NN-BPI played a regulating role in the oxidation potential of the compounds.All the non-doped devices exhibit dual emission.The NN-PPI based device has the best performance:the maximum brightness of 5199 cd m^-2,the maximum efficiency of 2.24 cd A^-1,and the color coordinates of(0.41,0.45).(2)Two novel phenanthroimidazole derivatives,BAPI and BCPI,were designed and synthesized by introducing a large steric hindrance structure group tetrapenyl methane into the N-1 of phenanthroimidazole,and a carbazole/triphenylamine group with hole transport property in C-2 position.The effects of steric hindrance and carbazole/triphenylamine groups on the photophysical and electrochemical properties of the compounds were investigated.Two kinds of light-emitting materials were used to fabricate non-doped devices and their electroluminescence properties were investigated.All the non-doped devices showed wide emission with white-like color.The non-doped device based on BAPI has the maximum brightness of 1190 cd m^-2,maximum efficiency of 1.0 cd A^-1,and color coordinates of(0.29,0.28).