| In the past two decades,organic light-emitting diodes(OLEDs)have shown broad application prospects in the field of flat panel display and solid-state lighting.However,there are still some problems to be solved in the further commercialization.Although the electroluminescence performance for red and green light materials has reached the practical standard,the brightness and efficiency of the blue light material are still low.The wide energy gap of the blue light material is not conducive to the injection of carriers from the transport layer to the light-emitting layer.In the electroluminescent device,the luminescent material is mostly present in the form of a film,but the generation of the exciplex and the excimer in the solid state will cause the conventional luminescent molecules to aggregate and the fluorescence quenching effect.In 2001,the discovery of aggregation-induced emission molecules can fundamentally solve the problem of solid-state fluorescence quenching of traditional luminescent molecules,which are highly promising organic electroluminescent materials due to their high solid-state luminescence efficiency.At present,many high-performance molecules have been reported,but reports based on blue and deep blue molecules are still rare because of their wide energy gap.Therefore,how to design and synthesize high-efficiency blue light molecules is still one of the difficult problems in current research.Our work designed and developed a series of new pyrene-based blue aggregate induced emission(AIE)materials and fabricated their OLED devices.7-tert-butyl-1,3-diphenyl-5,9-dibromofluorene,7-tert-butyl-1,3,5,9-tetrabromoindole and 2,7-di-tert-butyl-4,5,9,10-tetrabromofluorene was used as a starting material to introduce AIE chromophore tetraphenylvinyl(TPE)and triphenylvinyl(TriPE)to construct a novel pyrene-based AIE molecule.Their thermal stability,chemical structure,AIE photophysical,electrochemical and electroluminescence properties of these materials were also investigated.The first chapter mainly introduces the AIE phenomenon and basic principles,material types and applications,and expounds the research ideas of this paper.In the second chapter,7-tert-butyl-1,3-diphenyl-5,9-dibromofluorene was used as the starting material to introduce AIE chromophore(TPE or TriPE)to get Two novel butterfly-shaped pyrene-based blue AIE material molecules(Py(5,9)BTPE and Py(5,9)BTriPE)by Suzuki coupling reaction.The two material molecules have good thermal stability(Td>300?).TPE/TriPE with AIE properties are integrated into the 5-,9-position of pyrene with a large optical band gap,and the highly distorted molecular conformations of the AIE system provide these compounds bright blue luminescence in the solid state.The undoped OLED based on Py(5,9)BTPE exhibits sky-blue emission with CIE coordinates of(0.19,0.28),maximum external quantum efficiency(EQEmax)of 3.36%,maximum current efficiency(CEmax)of 6.51 cd A-1.and a low efficiency roll-off.In the third chapter,two novel butterfly-shaped pyrene-based blue material molecules(Py(1,3,5,9)TTPE and Py(1,3,5,9)TTriPE)were successfully constructed with 7-tert-butyl-1,3,5,9-tetrabromofluorene as starting material.These materials have good thermal stability(Td>400?)and electrochemical stability.Py(1,3,5,9)TTPE exhibits typical AIE characteristics,high-efficiency solid-state fluorescence efficiency,and its nondoped electroluminescent device exhibits excellent performance with an EQE of up to 4.10%.In the fourth chapter,we try to construct AIE luminescent molecules in the 4,5,9,10-K region of pyrene core with 2,7-di-tert-butyl-4,5,9,10-tetrabromofluorene as starting material.A new pyrene-based AIE material molecule(Py(4,5,9,10)TTPE)was successfully constructed by Suzuki coupling reaction.Py(4,5,9,10)TTPE has typical AIE properties,and its nondoped OLED exhibits good performance at 476 nm.Finally,the content of this paper and the development of AIE OLEDs are summarized and prospected. |
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