Synthesis And Photoelectric Properties Of Tetraphenylethene Derivatives With Aggregation-Induced Emission

Many conjugated organic emitters are highly emissive in their dilute solutions but become weakly luminescent when fabricated into thin film, which is called aggregation caused quenching (ACQ). The luminescent materials are practically utilized in the solid state or thin films commonly, prohibiting the application in organic light-emitting diodes (OLED). However, aggregation-induced emission (AIE) materials are promising candidates for OLED, tetraphenylethylene is the typical compound with AIE active.In this dissertation, three novel compounds based on teraphenylethylene with AIE active are synthesized, and characterized by IR、1H NMR、13C NMR and MS. It reflected that TPE-TPA and TPE-2TPA are not only AIE active materials but also hole transport materials.The optical properties of three compounds were studied that Uv-vis absorption spectra and fluorescence spectra were affected by solvent, which of TPE-TPA occurs redshift, while that of TPE-2TPA and TPE-TA occurs blueshift in polar solvent.TPE-TPA, TPE-2TPA and TPE-TA in dilute THF solution are weakly emissive. However, when water is added into the THF solution, the PL intensity is greatly increased, which indicates that they are AIE active materials. To explore the AIE mechanism, the flurescence intensity that affected by viscosity was researched; it discovered that the fluorescence intensity of TPE-TPA increases when the fraction of glycerin becomes biger in glycerin and methanol solution. In the view of experiment, it proposed that phenyl rotations were prohibited by addition of glycerin, decreasing the nonradiative routes, then, the energy in excited state emits in the form of fluorescence. In addition, there are highter fluorescence quantum yield of TPE-TPA (0.7636) and TPE-2TPA (0.7006) compared to TPE-TA (0.1381) in THF solution,Electrochmical property indrected that the ionization potential for TPE-TPA and TPE-2TPA is close to the work function of anode, reflecting that they are good electron-transporting materials. Then, an organic light-emitting diode that ITO/m-TDATA (30nm)/TPE-TPA(30nm)/Alq3(50nm)/ LiF(1nm)/ Al(100nm)was fabricated while TPE-TPA was photogenic layer. The color cooridnate was (0.27,0.44) and the onset potenial was 7V. Hence, TPE-TPA is a good green light-emitting material.Theory study on TPE-TPA and TPE-TA in ground state and excited state indirected that the configurations of them are propeller-shaped structures and phenyl ring can rotations, which are responsible for aggregation-induced emission. The reason is that propeller-shaped configurations increase the intermolecular distance, decreasing the π-π stacking interaction, some of caculated results have been compared with the experimental data. The results indicate that the theoretical calculating results could be well confirmed by the experimental data, indicating that the quantum chemistry calculation method canbe used to study the structures-properties relationship of these compounds to overcome the difficulties caused by the experiment limitations.