Synthesis And Properties Of Carbazole-Acridine Compound With Both AIE And TADF Properties

Since C.W.Tang produced high-efficiency electroluminescent devices in 1987 and pioneered the new era of organic electroluminescence,people have begun to realize the potential of OLEDs and are committed to exploring high-performance electroluminescent materials and developing technologies for manufacturing devices.Until entering the current information age,high-performance OLED-based display panels have achieved great success in mobile phones,digital cameras and television applications.As the core part of the OLED device,the choice of the luminescent layer material directly determines the luminescent properties of the OLED device.The aggregation-induced emission(AIE)phenomenon,first reported by the Tang Benzhong team in 2001,provides access to a variety of luminescent organic materials.When dissolved in a good solvent,the AIE molecules do not illuminate or faintly illuminate,while they illuminate significantly in poor solvents or solids.Since AIE molecules perfectly solve the problem of aggregation induced quenching(ACQ),this material has broad prospects in applications such as chemistry,biosensing,cell imaging and OLED.And the thermally activated delayed fluorescent material(TADF)has a small single-triplet energy gap(?EST),Under the action of ambient heat,the triplet excitons are more efficiently upconverted to singlet exciton luminescence by the inverse intersystem,thereby harvesting singlet and triplet excitons,and nearly 100% internal quantum efficiency(IQE)can be achieved,theoretically.Based on the different properties of these two materials,new organic luminescent materials with both AIE and TADF properties was designed by combining AIE compounds and TADF compounds.This materials not only solves the ACQ effect of traditional luminescent materials,but also breaks the limitation of 25% exciton utilization of the traditional luminescent material,providing a feasible way to achieve efficient electroluminescent devices.Carbazole has a good hole transporting ability,and benzophenone is a common receptor unit.In this thesis,a novel AIE-TADF material containing carbazole structure and 9,9-dimethyl-9,10-dihydroacridine structure was designed by modifying benzophenone.Its structure was characterized by elemental analysis,NMR spectroscopy and mass spectrometry.In addition,its thermal stability,photophysical properties,electrochemical properties and electroluminescence(EL)properties were systematically studied.The concrete content includes the following:In chapter 1: The development history of OLED,luminescence mechanism and device structure are introduced in detail.The luminescence mechanism and research progress of aggregation-induced luminescent materials and thermally activated delayed fluorescent materials are comprehensively summarized.In addition,the molecular design and research status of AIE-TADF materials are summarized.Based on this research,the design idea of this thesis is finally put forward.In chapter 2: A D-A-D' type AIE-TADF molecule DCPDAPM with carbazole as the backbone,benzophenone as the acceptor group and 9,9-dimethyl-9,10-dihydroacridine as the donor was designed and synthesized by modified Ullmann coupling reaction,nucleophilic addition,oxidation reaction,etc.And the structure was characterized by elemental analysis,NMR spectroscopy and mass spectrometry.In addition,The electronic configuration,thermal stability,photophysical properties and electrochemical properties of DCPDAPM were also systematically studied.The results show that the twisted conformation of DCPDAPM can reduce the ?-? interaction and ACQ effect,and the small ?EST ensures that the realization of the RISC process proves the potential of TADF properties.What's more,the photoluminescence behavior of the compound in different THF/water ratio solutions also confirmed its AIE effect.By measuring the fluorescence and phosphorescence spectra of DCPDAPM,the small ?EST of DCPDAPM in the solid state was estimated.Secondly,its TADF characteristics were further confirmed by testing the oxygen sensitivity and temperature dependence of the compound.In summary,DCPDAPM is a new type of AIE-TADF material that is well suited for use in light emitting devices.In chapter 3: Using DCPDAPM and DCPDAPM doped into CBP as light-emitting layers,a non-doped OLED(device A)and doped OLEDs(device B,device C and device D)were fabricated.They have been thoroughly tested and studied for their electroluminescent(EL)properties.The test results show that both the undoped and doped devices exhibit excellent EL performance.Among them,the undoped device A exhibits a maximum luminance of 123371 cd m-2,a maximum current efficiency of 26.88 cd A-1,a maximum power efficiency of 15.63 lm W-1,and an external quantum efficiency of 8.15%.The maximum brightness of the 6% doped device B is 67875 cd m-2,the maximum current efficiency is 40.68 cd A-1,the maximum power efficiency is 25.55 lm W-1,and the external quantum efficiency is 13.31%.The maximum brightness of device C doped with 10% is 89010 cd m-2,the maximum current efficiency is 50.14 cd A-1,the maximum power efficiency is 31.49 lm W-1,and the external quantum efficiency is 16.18%.And the device D with 20% doping exhibited the best maximum brightness,maximum current efficiency,maximum power efficiency and external quantum efficiency of 116100 cd m-2,61.83 cd A-1,40.45 lm W-1 and 19.67%,respectively.