Synthesis And Application Of Compounds Containing Carbonyl Groups Showing Aggregation-Induced Emission And Delayed Fluorescence Properties

Organic light-emitting diodes?OLEDs?,owing to the advantages of flexible bending,low energy consumption,rapid response,and low cost,have received extensive attention from scientific researchers.Among various luminescent materials used for OLED devices,delayed fluorescence materials have small?E_ST between the singlet state and the triplet state,and the triplet excitons can be changed to the singlet excitons via reverse intersystem crossing?RISC?processes,resulting in high excition utilization up to 100%.Molecules with aggregation-induced emission?AIE?properties can emit strong fluorescence in neat film,and provide high electroluminescence?EL?efficiency approaching the theoretical limit with a small roll-off in non-doped OLEDs.Therefore,endowing AIEgens with delayed fluorescence should be a feasible strategy to generate robust luminescent materials for OLED devices.In this thesis,a series of asymmetric D-A-D'molecules with carbonyl groups as electron-withdrawing groups were designed.These molecules combined AIE and delayed fluorescence properties,and showed good performances in both EL devices and mechanochromism application.In chapter 2,a series of asymmetric D-A-D'structures,CP-BP-PXZ,CP-BP-PTZ and CP-BP-DMAC,were designed using carbonyl groups as electron-withdrawing groups,and9-phenyl-9H-carbazole,phenoxazine,phenothiazine and 9,9-dimethyl-9,10-dihydroacridine as electron-donating groups.These molecules showed aggregation-induced delayed fluorescence?AIDF?properties,that is the emission intensity and delayed component lifetime of these compounds increased gradually as aggregates formed.These molecules exhibited higher fluorescence quantum yields in neat films compared to many conventional delayed fluorescence molecules.The nondoped OLED devices of these materials exhibited excellent EL efficiencies and stability.The best OLED showed EL efficiencies of 59.1 cd A^-1,65.7 lm W^-1,and 18.4%,and a neglible current efficiency roll-off of 1.2%at 1000 cd m^-2.In Chapter 3,new AIDF molecules,CC6-DBP-PXZ and CC6-DBP-DMAC,using carbonyl as the electron-withdrawing group were designed and applied in solution-processed OLED devices.The solubility of molecules was increased by increasing the molecular twisted configuration and introducing alkyl chains.The solution-processed OLED device using compound CC6-DBP-DMAC as emitter showed good EL performences with the maximum external quantum efficiency of 9.02%.The maximum external quantum efficiency of the non-doped device of the compound CC6-DBP-PXZ was 6.19%,the maximum luminance was33911 cd m^-2,and the roll-off was extremely low at high luminance.In Chapter 4,a series of asymmetric D-A-D'structures,Py-BP-PXZ,Py-BP-PTZ and Py-BP-DMAC,with AIE property were designed,using carbonyl groups as electron-withdrawinggroups,andpyrene,phenoxazine,phenothiazine,and9,9-dimethyl-9,10-dihydroacridine as electron-donating groups.Among them,the Py-BP-PTZ compound had mechanochromism property.The fluorescence color of the Py-BP-PTZ was changed from sky blue to yellow after grinding.Two crystals?CB and CG?with different fluorescence colors?sky-blue and yellow-green?were obtained by the solvent evaporation method.The crystal packings were analyzed and used to explain the mechanochromism property.At the same time,Py-BP-PTZ compound had the recoverability for mechanochromism,which enableed Py-BP-PTZ to be used in the fields of information recording,trademark anti-counterfeiting and security ink.