Organic Fluorescent Materials With Aggregation-Induced Emission Characteristics:Synthesis, Characterization And Applications

In2001, a novel phenomenon of aggregation-induced emission (AIE) was first found by Tang’s group. These AIE molecules are almost nonfluorescent in the solution but are induced to emit strongly as the aggregate formation, which is exact opposite to the emission behaviors of most conventional chromophores. This abnormal phenomenon has attracted considerable research attention and more and more research groups embark on the studies of the AIE mechanism and applications. AIE-active materials have found diverse potential applications in optoelectronic devices, chemosensors, fluorescent bioprobes, etc. For the sake of exploring new AIE-active materials, in this thesis, we synthesized and characterized two new kinds of compounds with AIE characteristic, including tetraphenylethene (TPE)-cored luminognes and naphthalene-substitutend ethenes. Their photophysical properties and applications in organic light-emitting diodes (OLEDs) were investigated and the structure-property relationship was discussed. The main results are outlined as follows:In the first chapter, we present the synthesis and characterization of a series of luminogens consisiting of a TPE core and triphenylamine, spirobifluorene and TPE peripheries. These compounds are processable and thermally stable, with high decomposition temperatures above at400℃. They are weakly fluorescent in the solution state but become emissive in the aggregate and film states, showing high solid-state fluorescence quantum yields up to99%. The OLEDs fabricated using these luminogens as light-emitting layers exhibit outstanding performances. The maximum luminance, maximum current efficiency and maximum external quantum yield are as high as25000cd/m2,11cd/A and3.5%, respectively, demonstrating that the TPE-cored luminogens are promising solid state emitters.In the second chapter, we present the synthesis and characterization of a series of naphthalene-substituted ethenes. These luminogens possess a propeller-like shape, and exhibit good solubility and thermal stability. Strong AIE effect was observed from these luminogens, revealing that, in addition to phenyl ring, the naphthalene ring can also serve as rotors to constructe AIE luminogens. The OLEDs based on the naphthalene-substituted ethenes show better performances that those based on TPE. These results are benefical to design of new AIE-active mateirlas with improved properties.