A molecular-design strategy for organic light-emitting diodes (OLEDs) is presented, which enables efficient, narrow-band, and stable electroluminescence through the use of a novel emitter, hBNCO-1. This emitter, designed by hybridizing organoboron-nitrogen and carbonyl fragments, achieves a fast reverse intersystem crossing rate of 1.79 × 10⁵ s⁻¹, leading to ultrapure emission, a maximum external quantum efficiency of over 40%, and a mild efficiency roll-off of 14% at 1000 cd·m⁻². The emitter also exhibits promising operational stability, with a device lifetime of 137 hours at 1000 cd·m⁻². The strategy involves optimizing the electronic structure to reduce the energy gap between singlet and triplet excited states and enhance spin-orbit coupling, which accelerates the reverse intersystem crossing process. The results demonstrate that the hBNCO-1-based OLEDs achieve high color purity, high efficiency, low efficiency roll-off, and long operational stability, representing state-of-the-art performance in OLEDs. The study highlights the importance of molecular design in achieving comprehensive performance in OLEDs.A molecular-design strategy for organic light-emitting diodes (OLEDs) is presented, which enables efficient, narrow-band, and stable electroluminescence through the use of a novel emitter, hBNCO-1. This emitter, designed by hybridizing organoboron-nitrogen and carbonyl fragments, achieves a fast reverse intersystem crossing rate of 1.79 × 10⁵ s⁻¹, leading to ultrapure emission, a maximum external quantum efficiency of over 40%, and a mild efficiency roll-off of 14% at 1000 cd·m⁻². The emitter also exhibits promising operational stability, with a device lifetime of 137 hours at 1000 cd·m⁻². The strategy involves optimizing the electronic structure to reduce the energy gap between singlet and triplet excited states and enhance spin-orbit coupling, which accelerates the reverse intersystem crossing process. The results demonstrate that the hBNCO-1-based OLEDs achieve high color purity, high efficiency, low efficiency roll-off, and long operational stability, representing state-of-the-art performance in OLEDs. The study highlights the importance of molecular design in achieving comprehensive performance in OLEDs.