Main-Group Synergy in Carbazole Emitters: Enhancing Cyanostilbene Solid-State Emission to Near Unity Quantum Yield via Duryl-Bridged Dimesitylborane

Unlocking the full potential of solid-state organic luminophores remains a central challenge in materials chemistry, particularly in overcoming the limitations of traditional donor-acceptor (D-A) architectures. In this study, we introduce a pioneering frontier in main-group-organic hybrid design by presenting the foremost triarylborane-integrated carbazole-cyanostilbene (<b>CZ-CS</b>) conjugate (<b>TAB-CZ-CS)</b> featuring a duryl-linked dimesitylborane (TAB) unit strategically fused into the D-A framework to construct an Acceptor-Donor-π-Acceptor (A-D-π-A) system. This molecular blueprint capitalizes on the rigidifying character of -BMes₂ to minimize the nonradiative decay channels and unlock record level solid-state performance. Strikingly, <b>TAB-CZ-CS</b> displays a pronounced red-shifted emission at 518 nm with a near-unity photoluminescence quantum yield of 99.2% representing a > 4-fold enhancement over the TAB-only analogue <b>CZ-TAB</b> and a 50-fold fluorescence enhancement over the AIE-active <b>CZ-CS</b>. Moving beyond basic structure-property tuning, this system showcases a finely balanced interplay between AIE and ACQ, with maximum fluorescence observed at a 40% water fraction in mixed solvents before quenching effects prevail. Unlike conventional mechanochromic luminophores, the hybrid shows only minimal spectral shifts upon grinding, highlighting that its stimuli response behavior is governed by main-group induced steric effect and morphological changes. This work not only delivers a highly emissive solid-state material but also establishes a powerful and underexplored design strategy: harnessing TAB-based main-group synergy to elevate the emissive output of π-conjugated organic scaffolds. Our findings offer a transformative leap in the design of hybrid optoelectronic materials and pave the way for a next-generation of functional luminophores rooted in main-group chemistry.