Tetraphenylpyrazine-based chiral deep-blue dyes with high brightness for energy delivery

Abstract

The search for deep-blue dyes with high luminescence efficiency in the aggregate state and high brightness is particularly important in optoelectronic application. Herein, based on a typical aggregation-induced emission (AIE) unit of tetraphenylpyrazine (TPP), four dyes were prepared by connecting it with chiral binaphthyl units via an acetylenic bond. The use of the TPP unit is critical to aggregation-enhanced emission (AEE) and deep-blue emission, whereas the merging of the binaphthyl unit is beneficial for molecular conjugation to remarkably improve absorption, photoluminescence (PL) quantum efficiency and brightness. Besides, the binaphthyl unit can serve as an axially chiral source to endow the deep-blue dyes with chirality. It was revealed that attaching a longer alkoxy chain to the dyes facilitates the formation of helical self-assemblies determined by chiral transfer but leads to an aggregation-caused emission (ACQ) effect. Moreover, using these deep-blue dyes as energy donors for energy delivery, other emissions and pure white light emission can be generated effectively via an energy transfer process based on a rational mixture of donors and acceptors in PMMA films. The device fabricated by coating this film onto a blue LED also emitted distinct and stable white light. This work provides a flexible way to design high-performance blue materials for potential applications.