Synthesis And Properties Of Luminescent Materials Based On Tetraphenyethylene Unit

Recently,luminescent liquid crystal(LC)materials have attracted much more attention as a research hotspot of organic light-emitting diodes(OLEDs)because of its ordered property and fluidity.However,luminescent liquid crystal materials still have big challenges,such as difficult molecular design,emission quenching in the solid state and low emission efficiency.To address these issues,this dissertation proposed that integrating the aggregation-induced emission(AIE)into the luminescent liquid crystal molecules to enhance the emission efficiency in the neat films.Therefore,a series of AIE-LC materials based on tetraphenylethene units were designed and prepared.The molecular structures of these AIE-LC materials were confirmed via 1H NMR,13 C NMR and MALDI-TOF mass.Additionally,their photophysical properties,electrochemical and liquid crystal properties were systematically investigated by UV-vis absorption spectra,photoluminescent(PL)spectra,cyclic voltammetry(CV),thermal analysis and SAXS.The OLEDs devices using the blue-light AIE-LCs,named TPE-PBN and TPE-2PBN as the dopant and employing 1,3-Bis(N-carbazolyl)benzene(mCP)as the host matrix were fabricated.The relationship between molecular structure and electroluminescence properties were explored.In conclusion,the main research contents of this dissertation are listed below:1、Three AIE-LC materials with blue emission,named TPE-PBN,TPE-2PBN and TPE-4PBN,were designed and prepared,in which the tetraphenylethenephenylpyridine derivative is used as the emission core and 4-cynobiphenyl is employed as the mesogenic unit.The liquid crystalline property of the molecules was studied by thermal analysis,polarized optical microscope and SAXS.The photophysical property in the mixture of THF/H2 O was investigated by UV-vis and PL spectra.The research results demonstrated that all these molecules showed the strong AIE features.In addition,TPE-PBN and TPE-2PBN have high emission efficiencies of 71% and 81%,respectively,in the solid state.TPE-PBN,TPE-2PBN and TPE-4PBN possesses the liquid crystalline property which is dependent on the number of mesogenic unit in the molecules.Using TPE-PBN and TPE-2PBN as the dopant,a series of doped and non-doped OLEDs were fabricated.The doped OLEDswith the bluenish-green emission showed a best performance with a maximum luminance of 1612 cd/m2,current efficiency of 6.2 cd/A and EQE of 4.1 %.2、Encouraged by the previous works,a family of cyclometalated platinum complexes(Pt1 ~ Pt6)which contains the cyclometalating ligand of TPEphenylpyridine derivatives and the ancillary ligand of acetylacetone(acac)/acetylacetone derivatives were synthesized and characterized.The liquid crystalline and photophysical properties were explored in detail.We found that all platinum complexes showed intense emission both in solution and neat film.Additionally,the length of alkyl chains in the cyclometalating ligand has a minor effect on the absorption and emission properties of platinum complexes.On the other hand,all complexes have the thermotropic liquid crystalline properties,though only Pt1 presented the AIE feature.The dissertation has developed a series of liquid crystal luminescent materials based on tetraphenylethene unit,and explored the structure-property relationship of these luminescent liquid crystal materials.This research revealed the molecular rule of AIE-based luminescent liquid crystal materials,which paves a novel way for achieving high emission efficiency liquid crystal materials.