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.