Wide-range color-tunable polycyclo-heteraborin multi-resonance emitters containing B–N covalent bonds

Abstract

Boron- and nitrogen (BN)-fused polycyclic aromatic frameworks with amine-directed formation of B–N covalent bonds have the potential to form a new family of facile-synthesis multi-resonance luminophores, which, however, still face imperative challenges in diversifying the molecular design to narrow the emission bandwidth and tune the emission colors. Here, we demonstrate a strategic implementation of B–N bond containing polycyclo-heteraborin multi-resonance emitters with wide-range colors from deep-blue to yellow-green (442–552 nm), small full-width at half-maxima of only 19–28 nm and high photoluminescence efficiencies, by stepwise modifying the basic para B–π–B structures with heteroatoms. The corresponding electroluminescent devices show superior maximum external quantum efficiencies with an exceptional low-efficiency roll-off, retaining 21.0%, 23.6% and 22.1% for the sky-blue, green and yellow-green devices at a high luminance of 5000 cd m⁻², respectively.