Design,Synthesis And Optoelectronic Properties Of Thermally Activated Delayed Fluorescent Materials Based On Fluorene Derivatives

Organic light-emitting diodes(OLEDs)can emit light autonomously,and have a series of advantages such as thin,wide-angle display,fast response,low operating voltage and flexible display.Thermally activated delayed fluorescence(TADF)materials can convert triplet excitons into singlet excitons through reverse intersystem crossing(RISC)without the participation of heavy metal atoms,which enhances their theoretical quantum efficiency to 100%,and compared with phosphorescent materials,they are cheaper,hypotoxic,more environmentally friendly,and have great application prospects in the field of organic optoelectronics,especially in OLEDs flat display and lighting areas.However,TADF materials often encounter severe aggregate-caused quenching(ACQ)and are mostly single emission,which limits their further development and application.In view of the above problems,this thesis designed and synthesized a series of TADF materials based on fluorene derivatives,and characterized their photoelectric properties to explore the relationship between molecular structure,packing mode and luminescence behavior.The results achieved are as follows:(1)Pure organic RTP material Cz-W-SOF and ultraviolet AIE-TADF material DPA-W-SOF were synthesized by using fluorene as the bridging group and diphenylsulfone as the acceptor,respectively,and carbazole and diphenylamine as donors,respectively.The relationship between intermolecular interactions,stacking mode and RTP emission was discussed by analyzing their photophysical properties and crystal structures.(2)Seven fluorescent molecules with AIE properties were designed and synthesized.Among them,SODAMC-W-SOF,W-DSODMAC,SOPXZ-W-SOF and SPXZ-SPTZ exhibited TADF emission,W-DSOCz and W-DSODMAC can be used for evaporated devices because of their excellent thermodynamic stability,provided a novel AIE-TADF molecular design strategy.(3)Ten dual-emission TADF molecules were designed and synthesized using molecular inheritance strategy.Among them,PXZ-W-SOF exhibited pressure-induced bidirectional shifting characteristics in isotropic hydrostatic pressure measurement,CCz-CPTZ and CPTZ-SCz exhibited near white-light emission in a specific proportion of THF/water mixed solvent,provided a new molecular design strategy for dualemission TADF molecules.