Novel Organic Fluorescent Materials Based On Aromatic Amines And Their Oled Devices

Organic fluorescent materials have great potential in applications such as flat panel display,lighting and biological and chemical sensing,therefore the preparation of efficient organic fluorescent materials is one of the current research focuses.AIE active organic fluorescent materials have considerable emission efficiencies when aggregated,their highly distorted conformations provide a molecular design strategy for efficient solid-state light-emitting materials.In addition,the introduction of the donor-acceptor(D-A)structure can be used to construct intramolecular charge transfer state,which can effectively tune luminescent color of the material,while an appropriate degree of charge transfer and HOMO/LUMO orbital separation is beneficial to obtain HLCT(hybridized local and charge transfer)excited state or TADF(thermally activated delayed fluorescence)property.Electron-rich aromatic amines have a certain hole transport capability and high thermal stability,and are easy to be chemically modified to construct D-A structure,they are thus widely used in organic fluorescent materials.Based on the above considerations,this thesis is dedicated to preparing novel organic fluorescent materials based on aromatic amines and/or high-efficiency OLED devices,in which we made use of delocalized molecular conjugation,twisted conformation of AIE molecule and HLCT/TADF feature.At the same time of getting excellent performance,we strive to further investigate and clarify the structure-property relationship,providing feasible design strategies for similar materials.Details are as follows:(1)From the structural characteristics of AIE type and ACQ-type compounds,it can be inferred that solid-solution dual-efficient luminophores should have the following characteristics: twisted conformation in solid state and considerable rigidity in solution.Only if these two conditions are satisfied at the same time can dual-efficient emitters be obtained.We have observed a substantial quantum efficiency(13%)of triphenylamine in THF solution and came up with the concept of conjugation induced rigidity(CIR)effect.Combining CIR effect in solution state and twisted molecular conformation in solid state,we modified triphenylamine with AIE module-triphenyl ethylene(HTPE)and successfully acquired dual-efficient emission,which provides a feasible design strategy for the preparation of dual-state efficient fluorescent materials.(2)A green fluorescent material BDPACS was prepared,which contains a cyano diphenylethylene(CS)and two diphenylamines(DPA).BDPACS presents HLCT excited state in low-polarity solvents and its neat thin film.However,the performances of undoped OLED devices of BDPACS are poor.The doping technique enhanced the efficiency values of the OLED devices by more than tenfold.We proposed solid-state solvation effect can be utilized to adjust the excited state property of light-emitting material in an OLED,which provides new possibilities of achieving HLCT state and can expand the application scope of HLCT excited state in OLED devices.(3)By adjusting the electron-donating ability of the aromatic amines introduced to dicyanopyrazine,we achieved a full-color luminescence.We successively tuned the 2,3-dicyano-5,6-diphenylpyrazine's blue fluorescence to yellow green,orange and red luminescene.It's worth noting that the prepared red emitter has a high quantum efficiency of 43%.Due to the high thermal stability,high glass transition temperature of the compounds,and possible TADF feature,these materials may exhibit excellent performances in OLED devices.