Tetraphenylnaphthosiline (TPNS): a potential building block for deep-blue emitter featured aggregation-induced blue-shifted emission

Abstract

As a representative building block of AIEgens, 1,1,2,3,4,5-hexaphenylsilole (HPS) performs better in constructing high efficiency OLEDs owing to its high-electron affinity, however, its synthesis processes are too harsh, and it is difficult to achieve good fluorescence in wide-bandgap emitters. Following our reported “benzo-strategy” for constructing tetraphenylbenosilole (TPBS) derivatives, the naphthalene group was introduced to fuse six-membered rings containing silicon in this work, and a novel building block named naphthosiline (NS) was developed. Unlike the free radical process in the ring-closing reaction of TPBSs, the preparation of tetraphenylnaphthosiline (TPNS) is more universal to substrate selection via metal-catalyzed C–H active cyclization reaction, which is beneficial for subsequent structural optimization. Fortunately, the three TPNS-derived compounds not only inherited the AIE characteristics but also displayed deep-blue emission in the solid with obvious blueshifting from the solution state to the aggregated state. Employing electrochemical characterization, the high electron affinity of silicon-based heterocycles was also maintained, and their non-doped spin-coating OLEDs exhibited very impressive performance with better external quantum efficiencies (EQEs) of 2.0–3.5% and lower Commission Internationale de l’Eclairage (CIE) coordinate y value of 0.062–0.084, which might be due to their special σ*–π* intramolecular conjugation of the NS core. These results implied that TPNS should be a brilliant deep-blue emission building block in high-performance the blueemitter construction.