Novel violet emitting material synthesized by stepwise chemical reactions

Abstract

In this paper, we report the design and synthesis of a novel bipolar violet emitting molecule CzPySiSF. The carbazole and pyridine moieties are employed to facilitate charge injection and balance carrier transport, whereas the spirofluorene is used as the violet emitter. The three functional groups, i.e., carbazole, pyridine and spirofluorene, are connected to tetraphenylsilane in a stepwise fashion using classical coupling reactions such as Suzuki and Ullmann. The resultant bipolar molecule CzPySiSF exhibits very stable thermal properties and a uniform amorphous morphology. The introduction of spirofluorene greatly enhances the fluorescence quantum efficiency of the molecule; moreover the PL spectrum of CzPySiSF in THF is mainly located in the violet region. The EL spectrum of CzPySiSF matches well with the PL spectrum with a maximum at 408 nm. The violet OLED of CzPySiSF exhibits the maximum external quantum efficiency of 0.59%.