Tetraphenylbenzosilole: An AIE Building Block for Deep-Blue Emitters with High Performance in Nondoped Spin-Coating OLEDs

1,1,2,3,4,5-Hexaphenylsilole (HPS) is a star building block of aggregation-induced emission luminogens (AIEgens) in constructing OLED emitters. However, their development is obstructed by their complicated preparation and difficulty of achieving blue/deep-blue emission via structure modification and tuning. In this study, a benzo-group modification strategy was adopted to increase the skeleton rigidity and reduce the vibrational-rotational motion of peripheral substituted phenyl groups. The resulting building block, named tetraphenylbenzosilole (TPBS), was synthesized easily via a silyl radical cascade process with intermolecular radical cyclization. After the structure of the reaction substrate was tuned, four TPBS-based derivatives were obtained which not only inherited AIE characteristics from HPS but also exhibited high-efficiency deep-blue emission in the aggregated state thanks to their tuned HOMOs/LUMOs. Similar to HPS, propeller-like conformations in their single crystals were observed. In nondoped spin-coating OLEDs, these AIEgens all exhibited satisfactory performance with high EQEs (3.1-3.6%) at CIE coordinates of (0.15, 0.10), the best result reported so far for spin-coating-type AIEgens in blue nondoped OLEDs. All of the data showed the feasibility of our strategy for solving the shortage of AIEgens serving as building blocks for deep-blue emitters. We foresee the development of systems based on TPBS or its derivative materials inspired by this work.