Methoxy-Directed, Lithium-Free One-Shot Borylation for Tetraboron-, Pyridinic and Amino Nitrogen-Integrated PAHs With Ultra-Narrowband Thermally Activated Delayed Fluorescence.

Doping multiple boron and other heteroatoms into polycyclic aromatic hydrocarbons (PAHs) could induce the multiresonance effect and thus highly promising narrowband emitters, but their development is hindered by tricky synthesis. Here, we report the design and facile synthesis of a novel tetraboron-oxygen covalent bonds, nitrogen-integrated PAH (QBO-1) and its derivative with an additional pyridinic nitrogen doping (QBO-Py) using the same methoxy-directed, lithium-free one-shot borylation route on a gram scale. Both QBO-1 and QBO-Py emitters exhibit ultra-narrowband violet emission with full width at half-maximum (FWHM) values of 7.4 and 8.6 nm in toluene and 9.5 and 11.2 nm in organic light-emitting diodes (OLEDs), respectively. The electroluminescent results of QBO-1 represents the narrowest reported for organic systems in terms of in nanometers. Moreover, the strategically replacing the benzene-core in QBO-1 with a pyridine in QBO-Py substantially reduced singlet-triplet energy gap, thereby enabling QBO-Py with evident thermally activated delayed fluorescence properties and leading to high external quantum efficiency of 14.5% in OLEDs. This work pioneers the integration of pyridinic nitrogen in multi-boron PAHs, demonstrating its key role in simultaneously tuning the energy gap and suppressing spectral broadening, thus providing a new design route for high-purity, high-efficiency OLED emitters.