The paper presents a novel molecular-design strategy for organic light-emitting diodes (OLEDs) that combines organoboron-nitrogen and carbonyl (h-BNCO) fragments. This strategy results in a fast reverse intersystem crossing rate (kRISC) of 1.79 × 10^5 s^-1 in the designed emitter h-BNCO-1, leading to ultrapure emission, a maximum external quantum efficiency (EQE) of over 40%, and a mild efficiency roll-off of 14% at 1000 cd·m^-2. The OLED exploiting a binary emissive layer (EML) with h-BNCO-1 exhibits a narrow emission band with a full-width at half-maximum (FWHM) of 39 nm and CIE coordinates of (0.24, 0.71). Additionally, h-BNCO-1 shows promising operational stability, with a device lifetime of 137 hours at an initial brightness of 1000 cd·m^-2. The work provides a promising molecular-design strategy for OLEDs with high efficiency, color purity, low efficiency roll-off, and operational stability.The paper presents a novel molecular-design strategy for organic light-emitting diodes (OLEDs) that combines organoboron-nitrogen and carbonyl (h-BNCO) fragments. This strategy results in a fast reverse intersystem crossing rate (kRISC) of 1.79 × 10^5 s^-1 in the designed emitter h-BNCO-1, leading to ultrapure emission, a maximum external quantum efficiency (EQE) of over 40%, and a mild efficiency roll-off of 14% at 1000 cd·m^-2. The OLED exploiting a binary emissive layer (EML) with h-BNCO-1 exhibits a narrow emission band with a full-width at half-maximum (FWHM) of 39 nm and CIE coordinates of (0.24, 0.71). Additionally, h-BNCO-1 shows promising operational stability, with a device lifetime of 137 hours at an initial brightness of 1000 cd·m^-2. The work provides a promising molecular-design strategy for OLEDs with high efficiency, color purity, low efficiency roll-off, and operational stability.