Two boron atoms versus one: high-performance deep-blue multi-resonance thermally activated delayed fluorescence emitters

Two new deep-blue narrowband multi-resonant emitters, 1B-DTACrs and 2B-DTACrs, one of which showing thermally activated delayed fluorescence (TADF), based on boron, nitrogen, and oxygen doped nanographenes were designed and synthesized in good yields. Precise control of the extent of borylation was achieved by modulating the reaction temperature and stoichiometry of the Lewis acid in the reaction. A comprehensive structural, theoretical, photophysical, electrochemical, and electroluminescent study is presented. Both emitters possess high photoluminescence quantum yields of up to 83%, small full width at half maximums (FWHMs) of around 24 nm, and deep blue emissions of around 450 nm in mCBP films. Devices based on 2B-DTACrs showed high maximum external quantum effi-ciencies of 14.8% and a deep-blue emission at 447 nm together with Commission Internatio-nale de l’Éclairage coordinates of (0.150, 0.044), which are very close to the BT.2020 re-quirement for blue pixels.