Synthesis And Properties Of Organic Near-infrared Luminescent Materials Based On Quinoxaline Derivatives

Organic near-infrared luminescent materials have attracted the attention of global researchers due to their potential applications in biological imaging,optical communications,information security,display and other fields.Thermally activated delayed fluorescence（TADF）materials can pass through thermally activated reverse intersystem transitions,use singlet and triplet excitons to emit light,and the internal quantum efficiency can reach 100%.It is a hot spot in the research of organic light-emitting materials in recent years.This thesis systematically reviews the development status of near-infrared TADF materials and other new small-molecule near-infrared luminescent materials.In view of the current key scientific problems of TADF near-infrared luminescent materials,such as low luminous efficiency,luminous efficiency decreasing with the red shift of luminous wavelength,and unclear structure-activity relationship,three types of small molecule luminescent materials have been designed and synthesized.The molecular structure of the materials was characterized by proton nuclear magnetic resonance,carbon spectroscopy,and mass spectrometry;the thermal stability of these small molecule luminescent materials was studied by thermal weight loss analysis,ultraviolet absorption spectroscopy,steady-state transient photoluminescence spectroscopy,and cyclic voltammetry.Photophysical and electrochemical properties,analyzed the relationship between the molecular structure of small molecule luminescent materials and thermal properties,photophysical properties,and electrochemical properties,revealed the relationship between molecular structure and TADF near-infrared luminescence,obtained TADF near-infrared small Molecular luminescent materials and their near-infrared electroluminescent devices.The main research contents and results of this thesis are as follows:（1）Using phenylcarbazole as the donor unit,and using mono-and dicyanoquinoxaline acceptors,respectively,PCz-QCN and PCz-（QCN）₂ were constructed.We studied the effect of the number of acceptors on the thermal stability,photophysics,electrochemistry and electroluminescence properties of the compound.TheΔE_ST of the compounds PCz-QCN and PCz-（QCN）₂ are 0.33 and 0.35 e V,respectively;the emission in the solid film is 604 and 670 nm,respectively,and the PLQY is 95% and 88%,respectively;in the organic red photoluminescence device The maximum emission peaks of the compounds PCz-QCN and PCz-（QCN）₂ are 572 and 644 nm,respectively,and the maximum luminance is 913 and 1197cd m^-2,respectively.（2）Using dicyanoquinoxaline as the acceptor unit and phenylcarbazole,diphenylthiopheneamine,and triphenylamine as the donor unit respectively,the near-infrared TADF materials PCz-ph-QCN and DPA-Th Ph-QCN were constructed.We studied the influence of donor strength on the thermal stability,photophysics,electrochemistry and electroluminescence properties of the compound.TheΔE_ST of the three molecules were 0.16,0.17,and 0.09 eV,respectively.The emission of the compounds PCz-ph-QCN,DPA-Th Ph-QCN and TPA-ph-QCN in the solid film are 590,714 and 784 nm,respectively,and the PLQY is 29%,23% and 47%,respectively;In organic near-infrared electroluminescence devices,the maximum emission peaks of the compounds PCz-ph-QCN,DPA-ph-QCN and TPA-ph-QCN are 638,688 and 798 nm,respectively,and the maximum irradiance is 18643,26159 and 26695 mW Sr^-1 m^-2.（3）Using dicyanophenanthro[4,5-fgh]quinoxaline receptors,two near-infrared small molecules TPA-PyQCN and（^tBu）₂TPA-PyQCN were synthesized using triphenylamine and tert-butyltriphenylamine as donors,respectively.We studied the effects of the rigid structure of the acceptor and the strength of the donor on the thermal stability,photophysics,electrochemistry and electroluminescence properties of the compound.TheΔEST of the compounds TPA-PyQCN and （^tBu）₂TPA-PyQCN are 0.20 and 0.16 eV,respectively;the emission in the solid film is 669 and 726 nm,respectively,and the PLQY is 82% and 63%,respectively;in organic near-infrared electroluminescent devices Among them,the maximum emission peaks of the compounds TPA-PyQCN and （^tBu）₂TPA-PyQCN were 730 and 748 nm,respectively,and the maximum irradiance was 30718 and 24899 mW Sr^-1 m^-2,respectively.