The Carbazole Nuclear Dendritic Oligofluorenes Of Synthesis

Fluorene aroused great interesting since its easy modification, big energy gap and high photoluminescence efficiency. It is an important blue-emitting material. The branched oligofluorene is one kind of the most important fluorene derivatives. The oligomers have definite molecule structures. The aggregation of the molecules is limited. And they are easy to be processed. Therefore, it is important to develop new branched blue-emitting oligofluorene.In this paper, the carbazole moieties were used as a core, oligoflurenes were used as the branches, and pyridine rings served as the end-capped groups. Two series of V and Y shaped oligomers were synthesized. Carbazole can greatly increase the hole transporting. End-capped with pyridine can increase the electron transporting ability of the oligomers. The hyperbranched oligofluorenes have the excellent luminescence performance. All the oligomers were characterized by IR, MS and NMR spectra.Studying the photophysical properties, we can find that this kind of branch oligomers can effectively restrain the intermolecular aggregation. The fourth and fifith generations of the oligomers have the excellent spectrum stability. Meanwhile, we can tune up the number of fluorene to restrain the intermolecular charge transfer which causes the red shift at the same time of achieving the balance of carrier transfer and blue emitting. In addition, the phosphorescent spectrum showed that the materials have high triplet excited levels. The materials can be used as potential host material for blue-green phosphors.