Research On Luminescent Molecules With TPE And Carbazole Groups And Their RTP,ML Properties

Recently,the organic light-emitting materials were experiencing high-speed development.As some novel materials with HLCT,TADF characters were applied in OLED,the organic electroluminescence(EL)efficiency was much improved.And TADF material has even demonstrated high EL efficiency that equal to phosphorescent OLED.However,there were still challenges for the commercialization of OLED products,for example,the green and red light devices,in three-primary colors,have achieved breakthrough of EL efficiency and lifetime fitted to the practical application,but the blue light device encountered problem in lifetime and stabilization,because of the difficulty in carrier injection and transport result from wide band-gap.In 2001,the discovery of aggregation-induced emission(AIE)put forward new design concept for light-emitting materials,and lots of small molecules with excellent luminous performance were designed and synthesized accordingly.The field of AIE polymers was also developed rapidly,however,there were few applications in OLED,with relatively very low EL efficiency.On the other hand,the research on AIE mechanism revealed a great difference of photophysical process between the aggregate and solution states.In aggregate state,the non-radiative transition rate reduced as molecule vibration was largely suppressed,meanwhile,the intermolecular interaction was enhanced because of the closer intermolecular distance.Thus,there were lots of special luminescence phenomena occurred in the aggregation state,such as room temperature phosphorescence(RTP)and triboluminescence(TL).Crystallization was the most common method to achieve the RTP of organic molecules,and it has been realized that intermolecular interaction was vital to RTP in aggregate state,but how molecular arrangement affecting RTP was still unclear.TL is an ancient luminescent phenomenon,the inherent mechanism was not folly understood.The AIE brought new inspiration to the field of TL,and needs to develop more AIE type TL molecules for promoting the development of TL.This thesis focuses on the searching of organic light-emitting polymers,especially,the design and synthesis of AIE polymers with blue light emission.Besides,the thesis has also developed the RTP and TL materials,with exploration of luminescent mechanism on the level of molecular packing.Chapter 1:The organic electroluminescence,AIE polymer,organic RTP crystals and AIE type TL molecules were briefly reviewed:15 the introduction mechanism of photoluminescence and electroluminescence;2,the discovery of AIE mechanism and the application of AIE polymer in OLED;3,the mechanism and development of RTP and AIE type TL materials;4,the design ideas and research contents of the thesis.Chapter 2:Amide derivatives,CPM,CMPM and CMOPM,were designed and synthesized,which exhibited RTP character due to the strong spin orbital coupling effect of carbonyl and carbazole groups.The chemical structure and optical properties of compounds in monomer state were similar,however,large differences in single-crystals,RTP properties were found.The RTP of CPM is the strongest,with the luminous efficiency of 3.17%and the RTP lifetime of 748 ms at 530 nm.Chapter 3:Four acetenyls substituted tetraphenylethylene(TPE)derivative(TETPE)with TL character was designed and synthesized.Most of the previously reported TL molecules contain heteroatoms,which were important to enhance the intermolecular hydrogen bonding interaction.The electron cloud of acetenyl group was abundant,and the carbon atom in sp hybridization possesses the strongest electronegative,as a result,the terminal hydrogen atom exhibited the smallest pKa and strongest acidity.Thus,the acetenyls in TETPE could enhance intermolecular interactions.The research confirmed heteroatoms were not necessary for the production of TL,deepen the understanding of TL.Chapter 4:Tetraphenyl cyclopentadiene based "A4+B2" type hyperbranched polymer of CPI,CP2 and CP3,we're designed and synthesized,which exhibited high thermal stability and luminous efficiency.CPI based PLED devices with traditional host material mCP achieved excellent EL efficiency,and the maximum external quantum efficiency,current efficiency and the power efficiency were 6.36%,10.64 cd A-1 and 6.68 lm W-1,respectively.The EL efficiency was further improved by replacing the host with TADF material of CzAcSF,and the corresponging maximum efficiency were 9.74%,16.96 cd A-1 and 10.75 lm W-1,respectively.Chapter 5:PI,P2 and P3,with simple chemical structure and high luminous efficiency,were designed and synthesized,through the McMurry coupling reaction.The maximum external quantum efficiency,current efficiency and power efficiency of P1 were 8.80%,3.40 cd A-1 and 1.52 lm W-1,respectively,with CIE chromaticity coordinate of(0.16,0.06).This high external quantum efficiency may result from triplet-triplet annihilation effect.Chapter 6:The "A4+B2" type hyperbranched polymer,HPF and HPC,based on meta-position connection type of TPE,were designed and synthesized.The luminescence was blue-shift because of the larger intramolecular rotation barrier.The CIE chromaticity coordinates of the corresponding PLED based on polymers were(0.25,0.35)and(0.32,0.37),and their maximum current efficiency were 1.44,0.39 cd A-1,respectively.Chapter 7:The diphenylsulfone based linear polymers of PDCz,PCDCz,PCDFlu,PCDTPE,and hyperbranched polymer of HPCDTPA,were designed and synthesized,all of which exhibited excellent luminous efficiencies.Because of the introduction of TPE moiety,PCDTPE was AIE active,and emitted in sky-blue,while other polymers were deep-blue.The non-doped and CzSi-doped PLED devices based on these polymers were fabricated.The EL performance revealed that the emission spectra were blue-shift with adoption of host material,but EL efficiency decreased.PCDTPE demonstrated the best EL performance with maximum brightness of 1663.0 cd m'2,and maximum external quantum efficiency,current efficiency and power efficiency of 2.58%,5.73 cd A-1 and 4.50 lm W-1,respectively.Chapter 8:The benzophenone based linear polymer of PCBPF,PCBPTPE and hyper-branched polymer of HPCBPTPA,were designed and synthesized.Because the benzophenone can promote singlet excitons turn to triplet one with the assistance of strong spin-orbital coupling effect,the polymers exhibited weak TADF property.Their PLED devices had very good EL property,and PCFBP achieved the best performance,with the maximum external quantum efficiency,current efficiency and power efficiency of 1.71%,2.65 cd A-1 and 1.19 lm W-1,respectively.