Synthesis And Luminescent Properties Of Organic Small Molecular Light-Emitting Materials Based On Condensed Aza-Heterocycles

So far,organic light emitting diodes(OLEDs)have been proposed for more than 30 years.The research and application of photoelectric devices and their prospects have been significantly improved,both in the industrial field and in scientific research studios.They have been widely used in high-performance materials such as flat panel displays,photovoltaic devices(OPVs),organic field effect transistors(OFET),energy storage,sensors,and other fields.The rigid conjugated structure formed by nitrogen-containing fused ring groups is conducive to the effective injection and transmission of electric charges.It has strong chemical modification,high fluorescence quantum efficiency,unique photophysical and electrochemical properties,and high thermal stability,and can be used as organic luminescent materials.This article mainly focuses on the oxidation of pyrene in the K region(4,5 positions)to a certain extent,and further modification of pyrene to form a series of D-A type molecules.At the same time,selecting 9,10-phenanthraquinone as the core skeleton,six small molecular luminescent materials based on pyrene and phenanthroline derivatives were prepared by grafting different structural units to balance the electron push and pull effect,regulate the luminescence color and intensity,and study the basic photophysical and electrochemical properties of the luminescent materials,as well as the electroluminescent properties of some materials.The specific work is as follows:In the first part,pyrenediazine plays the role of electron pulling core skeleton,to graft with different electron giving abilities phenothiazine and phenoxazine onto the pyrene zine core.Design and synthesize two donor receptor(D-A)type structural molecules Py-PTZ and Py-PXZ.By high-resolution mass spectrometry,nuclear magnetic resonance spectroscopy charactering chemical structures of the compounds Py-PTZ and Py-PXZ.Ultraviolet absorption,fluorescence spectroscopy and their electrochemical properties further studies thermal stability and optical properties,and discuss their basic electroluminescent device performances.The maximum PL emission spectra of compounds Py-PTZ and Py-PXZ in chloroform solution are located at 510 nm and 474 nm,respectively.The fluorescence emission spectra in the solution show weak green and orange light.Considering that the compound hardly emits light in the solution and the solid emits strong light,we measured the fluorescence quantum of the material in the solid powder state yields were 9.71%and 7.35%,respectively.Charactering the performances of doped devices based on materials Py-PTZ and Py-PXZ,and show better performance when the doping concentration is 5 wt%.The brightness of Py-PTZ can reach2570 cd/m~2,and the maximum external quantum efficiency(EQE)is 1.64%;The maximum current efficiency is 2.67 cd/A;The external quantum efficiency of Py-PXZ reaches 3.81%,the brightness can reach 4554 cd/m~2,and the maximum current efficiency is 6.39 cd/A.In the second part,in order to further improve the solubility of materials,using carbazole with tertiary butyl as an electron donor group,respectively to graft onto the electron pulling core skeletons phenanthroline and pyrene-diamine with different conjugation degrees,selected the core skeletons with different conjugation degrees,design and synthesize two kinds of D-A configuration small molecule luminescent materials Py-Cz and PI-Cz,and study the characteristics of carrier transport equilibrium and luminescence intensity.Test and characterize the photophysical properties,electrochemical properties and electroluminescence properties of compounds Py-Cz and PI-Cz.The maximum PL emission of compounds Py-Cz and PI-Cz in dichloromethane solution are located at 558 nm and 548 nm,respectively.The fluorescence emission spectrum in solution exhibits orange-yellow emitters.The maximum PL emission measured in solid powder are located at 527 nm and 529 nm,respectively.The fluorescence quantum yield of compound Py-Cz in dichloromethane solution is 45.87%.We characterize the doped device performance based on the material Py-Cz,and we find that the compound of Py-Cz exhibit excellent device performance at a doping concentration of 5 wt%.The brightness of Py-Cz can reach 4803 cd/m~2,the maximum current efficiency is 5.9 cd/A,and the external quantum efficiency reaches 1.86%.In the third part,using pyrene-diamine as the core skeleton of luminescent materials,the strong electron withdrawing triazine group and electron donating trianiline unit are grafted onto the pyrene-diamine core skeleton to modify the molecular structure of two fluorescent materials Py-TRZ and Py-TPA.In this section,the chemical structures of compounds Py-TRZ and PI-TRZ are also characterized by high-resolution mass spectrometry,nuclear magnetic resonance spectroscopy,ultraviolet absorption,and fluorescence spectroscopy,and their electrochemical properties,thermal stability,and optical properties were studied.The maximum emission peaks of the PL spectra of compounds Py-TRZ and Py-TPA in dichloromethane solution were located at 485 nm and 592 nm,respectively.Solid state films had strong emissions at 466 nm and 532nm,fluorescence quantum yield(Фf)of compound Py-TRZ in dichloromethane solution and fluorescence lifetime(τ)are 44.53%and 3.19 ns,respectively.