Synthesis And Properties Of Pyrimidine-based Iridium Complexes And Triazine-based Fluorescent Materials

Organic light-emitting diodes(OLEDs)are widely used in flat display,solid-state lighting,wearable devices and other fields due to their outstanding advantages.Although OLEDs have been put into commercial applications,how to reduce costs and improve device stability and efficiency is still the direction that needs to be continued.In OLEDs,the light-emitting layer plays an important role in the performance of the device,so the development of new light-emitting layer materials plays an important role in improving the performance of OLEDs and reducing the cost of OLEDs.The light-emitting layer of hybrid OLEDs is doped with guest light-emitting material in the host material.The host material plays the role of transporting carriers and reduces the lighting voltage,while the light-emitting material plays the role of converting electrical energy into light energy.Its own properties play a key role in the energy transfer between host and guest materials,the luminous color and color purity of the device.Therefore,the development of new light-emitting materials will play a very important role in promoting the further development of OLEDs.The main work of this paper was to design and synthesize new luminescent materials.We have synthesized a series of phenylpyrimidine-based small molecule cyclometal phosphorescent iridium(?)complexe sand D-A structure with carbazole derivatives based on triazine as acceptor organic thermally activated delayed fluorescence materials(TADF),then we have studied their photophysical properties and electrochemical properties.In the first chapter,we mainly reviewed some of the photophysical properties of organic small molecule light-emitting materials and the influence of molecular structure on their physical properties,and introduced the working principles,performance parameters and calculations of OLED devices.In Chapter 2,we used phenylpyrimidine as the main ligand,and modified the structure of the main ligand by fluorine substitution at different positions.Then we coordi Natureed the synthesized main ligand with the trivalent iridium ion to form dimerization.Four small-molecule phosphorescent iridium(?)complexes(triF-pyr)₂IrPic,(diF-pyr)₂IrPic,(triF-pyr)₂IrAcac,(diF-pyr)₂IrAcac was synthesized.Through the study of its photophysical and electrochemical properties:1.The fluorine substitution reduced the energy of the molecular LUMO orbital due to its electron withdrawing effect which made the emission red shift,2.Compared with the auxiliary ligand acetylacetone,the ligand emission peak of the iridium(?)complex with picolinic acid as the auxiliary ligand was weaker,which indicated that the complex with picolinic acid as the auxiliary ligand was more beneficial to the inter-ligand energy transfer.The HOMO and LUMO energy level energies and corresponding band gaps calculated by studying the electrochemical properties of the complexes.It was found that the Stokes shift of the complexes based on picolinic acid as an auxiliary ligand was smaller.This indicated that the complex based on picolinic acid as an auxiliary ligand reduced the energy loss during the radiation transition of excited state molecules.In Chapter 3,we used triazine as the electron acceptor unit and 10,15-dihydro-5H-diindolo[3,2-A:3',2'-C]carbazole as the electron donor units,Ph-TRZ-TAT with D-A structure were synthesized with phenyl on the triazine 4 and 6-respectively.The introduction of phenyl substitution in the acceptor triazine,due to the conjugation effect between the phenyl group and the triazine,delocalized the LUMO orbital on the triazine to the phenyl group,which stabilized the LUMO orbital and reduced the LUMO energy level and led to emission redshift.In addition,due to the good thermodynamic stability and electron do Natureing ability of the electron donor unit itself,the interaction between the donor and acceptor was enhanced,and the thermodynamic stability of Ph-TRZ-TAT was improved.The decomposition temperature of Ph-TRZ-TAT was as high as 444.3?.