Synthesis And Application Of Phenylethene-carbazole Fluorescent Materials With AIE Characteristic

The novel phenomenon of aggregation-induced emission(AIE)was first found by Tang’s group.They discovered that a series of propeller-like luminogens being practically non-fluorescent in solutions became highly emissive upon aggregate formation and called this abnormal phenomenon aggregation-induced emission(AIE).Considerable attention has been attracted to the AIE phenomenon,and many organic luminescent materials with AIE property have been reported and showed their good applications in organic light-emitting diodes(OLED),fluorescent probes,chemosensors,and bioimaging,etc.So far,AIE-active compounds that have been synthesized include silole derivatives,multiaryl-substituted ethane compounds,cyano-substituted diphenylethene compounds,pyran and other small molecule compounds,and polymers.Among them,phenylethene and its derivatives have received much attention because of their advantages such as simple molecular structures,facile synthesis,easy functionalization,and striking AIE effect.For the sake of developing new efficient solid-state emissive materials,in this thesis,we successfully synthesized two phenylethene-carbazole fluorescent materials with AIE characteristic by introducing conventional carbazole chromphores and bulked dimesitylboron groups to phenylethene structure,and fully characterized their molecule structures.Their photophysical properties,AIE properties,thermal properties,electrochemical properties and their applications in OLED devices were studied.The main contents are summarized as follows:(1)The design methods,recent progress application in OLEDs and development status of AIE materials were reviewed.On the basis of these,the design idea of this dissertation was put forward.(2)Two compounds,DETPCZ and DECZDPE,consisting of phenylethene-carbazole core and dimesitylboron peripheries were synthesized via Friedel-Crafts reaction,Mc Murry coupling reaction,and nucleophilic substitution reaction,and characterized by multiple methods.(3)The thermal properties of the two compounds were studied by thermal analysis,which indicated that DETPCZ and DECZDPE have good thermal and morphological stability.The fluorescence spectra of DETPCZ and DECZDPE in various THF-water mixtures were recorded,which confirmed their AIE characteristics.The geometrical and electronic properties of the two compounds were investigated by density functional theory.The results showed that both of them possess twisted conformations,which efficiently hampers the close π-π stacking interactions between the chromophores,and promotes efficient solid-state emissions.On the other hand,the electron distribution revealed that the two compounds have intramolecular-charge transfer(ICT),which was verified by the UV spectra.The electrochemical properties of DETPCZ and DECZDPE were measured by cyclic voltammetry.Thus the cyclic voltammetry curves and the highest occupied molecular orbital(HOMO)and the lowest unoccupied molecular orbital(LUMO)energies were obtained.Eventually,two non-doped OLEDs,Device I and II,were fabricated by utilizing DETPCZ and DECZDPE as emitting layer,respectively.Device I exhibits a bright sky blue emission with maximum luminance and maximum current efficiency of 13930 cd/m2 and 4.74 cd/A,respectively.Device II gives blue-green light with maximum luminance and maximum current efficiency of 15780 cd/m2 and 6.90 cd/A,respectively.