Synthesis And Properties Of Dendritic Derivatives Of (8-hydroxyquinoline) Aluminium

Organic light-emitting materials and diodes have been and are attracting much research attentions due to their potential applications in next generation large-area flat-panel displays and semiconducting lighting sources.As one of the most successful electroluminescent materials,(8-hydroxyquinoline) aluminum(Alq₃) is characterized by many advantages such as high fluorescent quantum yield,excellent thermal stability,high glass transition temperature and excellent morphological stability,electron transporting nature,good film formation ability via vacuum deposition,and so on.On the other hand,Alq₃ is not well solueable in common organic solvents,consequently it has to be purified by repeated train sublimation technique.Furthermore,the electron transporting mobility of is still lower by one to three orders of magnitude than the hole drift mobility of most p-type organic semiconductors.Therefore,there have been a lot of research attempts to improve solubility and electron mobility of Alq₃ derivatives in recent years.In order to explore the possibility in this dissertation to make films and devices of Alq₃ derivatives by solution processable techniques such as spin coating,two dendritic Alq₃ derivatives were designed in such a way that polybenzene dendrons of the first and second generation were introduced to the 8-hydroxyquinoline ligands with the expectation to improve the solubility and molecular weights of the resulted dendritic complexes.The dendritic ligands were first synthesized through Diels-Alder cycloaddition reaction between the corresponding intermediates.The target aluminum complexes were obtained via complexation of the ligands and AlEt₃.The yielded dendritic Alq₃ derivatives of the first and second generation,i.e.G1 and G2 are well soluable in common organic solvents such as chloroform,dichloromethane,toluene and so on in comparison to small molecular analogue Alq₃.These dendritic complexes could be facially purified via recrystallization to reach the high purify demanded by device applications.The spectroscopy data revealed that the dendritic G1 and G2 are green fluorescent,with similar maximum emission wavelength and spectra to Alq₃.The fluorescent quantum yield of G1 and G2 were measured to be ca.13%in dilute solution,slightly lower than that of Alq₃.The thermalgravimetric analysis(TGA) measurements showed that G1 and G2 have extremely high thermal decomposition temperature,confirming that these dendritic Alq₃ derivatives are remarkably thermal stable.Other properties and device behavior of the present derivatives are in the process of investigation.The combination of the excellent solubility,dendritic molecular structures and properly high molecular weights of the obtained Alq₃ derivatives G1 and G2 in this study confirms the possibility to realize "solution processable Alq₃-based electron transporting materials"...