Synthesis Of New Type Silicon Heterocyclic Materials With Aggregation-Induced Emission In The Applications Of Electroluminescence

Aggregation-induced emission（AIE）refers to the phenomenon that a class of luminogens exhibits a nearly non-emissive nature in the unimolecular state but their bright emission returns in aggregate or film states,which is the opposite of the traditional aggregation-caused quenching（ACQ）phenomenon.1,1,2,3,4,5-Hexaphenylsilole（HPS）is a representative building block of AIEgens.Due to the uniqueσ*-π*conjugation effect of silole,HPS and its derivatives possess high electron affinity and a low-lying LUMO energy level,coupled with high efficiency solid-state luminous efficiency,so that they can be used in field of organic light-emitting diodes（OLED）with huge application potential.At the same time,after nearly 30 years of development in the OLED field,high-efficiency green and red luminogens have gradually moved towards commercialization,but blue luminogens with excellent performance are still quite scarce.On the other hand,OLED film forming processes mainly include spin-coating method and vacuum evaporation method.Although the performance and stability of the device prepared by the spin-coating method are still not ideal,it can greatly reduce the preparation cost of the OLED device,which is more conducive to commercialization and mass production.However,the currently reported HPS derivatives are difficult to synthesize and their emission are in the range of green to red with low color purity.Therefore,if HPS can be modified in a simple and efficient way to design a class of high-efficiency blue silicon heterocycles used in the emitting layer of OLED devices by spin-coating method with uniqueσ*-π*conjugated electronic structure and obvious AIE performance,this material system can not only develop a new type of blue building block for the AIE family making up for the vacancy of AIE material in blue silicon heterocycles,but also greatly promote the development of the OLED field.Based on this,the specific research content is as follows:In Chapter 2,in order to retain the AIE properties of HPS and theσ*-π*conjugated electronic structure of the silole,while realizing valuable blue light emission,we adopted a“benzo-strategy”of replacing the two phenyl groups of HPS at the 2,3-position with one phenyl group merged with the silole core,and a series of benzosilole derivatives TPBS-H,TPBS-F,TPBS-B and TPBS-M have been synthesized.The EL emission peaks of the non-doped spin-coated OLED devices based on these AIEgens are all around 438 nm with good color purity,and the CIE coordinates are all around the deep blue emission region of（0.15,0.10）.When TPBS-F was employed as the emitting layer,its device exhibited excellent comprehensive performance with L_max of 2139 cd m^-2 and maximum EQE of 3.6%@CIE（0.154,0.104）,a very good value for non-doped deep-blue OLEDs and the best result for spin-coating-type AIEgens so far.In Chapter 3,the blue-light AIE molecular design strategy in Chapter 2 was extended to the six-membered silicic ring.A new type of AIE building block containing the naphthosilicic six-membered ring（NS）structure was designed,and a series of deep blue AIEgens TPNS-H,TPNS-F and TPNS-M were synthesized.Structurally,NS core forms a large conjugate plane,but the position of the silicon atom is offset to a certain extent from the plane.These luminogens show obvious aggregation induced blue-shifted emission（AIBSE）phenomenon.The non-doped spin-coated OLED devices of TPNS derivatives exhibit deep blue emission and high color purity with narrow full-width at half-maximum of only about 30 nm.Among them,the device based on TPNS-H exhibited excellent comprehensive performance withη_c,max of 2.1 cd A^-1,η_p,max of 2.0 lm W^-1 and maximum EQE of 3.5%@CIE（0.162,0.062）.In Chapter 4,in order to obtain a series of bluer AIEgens,we envisaged to reduce the induction effect of the phenyl group on the NS core.Therefore,we replaced the two phenyl groups at position 1 of the TPNS derivatives with a methyl group,and designed three deep blue AIEgens MPNS-H,MPNS-F and MPNS-M.These luminogens have remarkable AIE properties and show more obvious AIBSE phenomenon.The non-doped spin-coated OLED devices prepared by this series of materials with ideal efficiency,not only achieved high standards of deep blue emission,but also further improved the blue color purity.However,after the introduction of the methyl group at position 1,the compound is easy to form a simple and regular accumulation and to crystallize during the preparation and working process of the device,resulting in a decrease in the stability of the device,which is a problem that needs improvement in the future.