Synthesis And Properties Of Functional Organic Small Molecule Luminescent Materials

Organic light emitting diodes(OLEDs)have attracted wide attention due to their advantages such as self-emission,wide viewing angle,low energy consumption,low cost,flexibility,high contrast,fast response speed,wide temperature range,and so on.As the core of OLED light-emitting technology,organic electroluminescent materials have become the focus of attention.In recent years,red and green luminescent materials in commercial OLEDs have developed rapidly,while blue luminescent materials are relatively backward.Therefore,the preparation of commercially high-efficiency OLED blue luminescent materials has become a research hotspot.In this paper,we synthesized organic small molecule materials with blue light emission,high performance,simple structure and aggregation-induced emission characteristics.The specific research content is as follows:In the first part,two organic light-emitting materials,SFX-CS and SFX-CD were synthesized by using diethylaminocoumarin as the luminescent group and the spironoxanthracene(SFX)as the molecular skeleton.Coumarin as a chromophore increases the fluorescence quantum yield of the molecule,and the nearly vertical spiral ring molecular structure in SFX hinders molecular accumulation and reduces the aggregation-induced quenching phenomenon.The thermal stability,electrochemical properties,photoluminescence properties and electroluminescence properties of the compounds SFX-CS and SFX-CD were studied.ITO/NPB(20 nm)/TBADN:Dopant(x wt%,30 nm)/TPBi(20 nm)/Liq(2 nm)/Al(100 nm)multilayer doped OLED devices were prepared by vacuum deposition.The compound SFX-CS showed better device efficiency with the maximum brightness of 6995cd/m~2,the maximum luminous efficiency of 8.24 cd/A,and the maximum external quantum efficiency of 3.86%at a 10%doping concentration.The compound SFX-CD shows the maximum brightness of 1285 cd/m~2 at a doping concentration of 7%,the maximum luminous efficiency of 2.26 cd/A,and the maximum external quantum efficiency of 2.26%.In the second part,three luminescent materials,NC-BP-NC,NC-BP-Ph-Cz and NC-BP-Cz-Me were designed with benzophenone as the electron-drawing group,diethylamine and carbazole as the electron-donating group,and coumarin as the luminescent group.The three compounds have high fluorescence quantum yields and good solubilities in common organic solvents.The fluorescence emission peaks of NC-BP-NC,NC-BP-Ph-Cz and NC-BP-Cz-Me are 477 nm,477 nm and 485 nm,respectively,all of which are blue light emission.The cyclic voltammetry was used to characterize the electrochemical properties of the three compounds.The HOMO energy levels of NC-BP-NC,NC-BP-Ph-Cz and NC-BP-Cz-Me were-5.37 eV,-5.10 eV and-5.28 eV.The LUMO energy levels were-2.73eV,-2.39 eV,and-2.58 eV,respectively.The density functional theory(DFT)was used to simulate the electron cloud distribution and molecular conformation.These compounds show good thermal stabilities and are expected to make progress in OLED applications.In the third part,two bipolar luminescent materials NC-Ph-FO and NC-TPE with tetrastyrene and fluorenone as electron-drawing groups,diethylamine group as electron-donating group,and coumarin as chromophore were designed and synthesized.The optical and electrochemical properties of the compounds NC-Ph-FO and NC-TPE were studied.The ultraviolet absorption peaks of NC-Ph-FO and NC-TPE are at 407 nm and 407nm,the fluorescence emission peaks are at 481 nm and 548 nm.The cyclic voltammetry was used to characterize the electrochemical properties of the two compounds.The HOMO energy levels of NC-Ph-FO and NC-TPE were-5.36 eV and-5.35 eV.The LUMO energy levels were-2.71 eV and-2.62 eV,respectively.The electron cloud distribution and molecular conformation of the two compounds were calculated using DFT.