Tailoring Ultra‐Narrowband Tetraborylated Multiple Resonance Emitter for High‐Performance Blue OLED

Abstract Ultra‐narrowband multiple resonance (MR) emitters are a key component in the fabrication of highly efficient and stable blue organic light‐emitting diodes (OLEDs). To explore the theoretical boundaries of wavelength and full width at half maximum (FWHM) in blue emitters, the currently narrowest boron‐based MR emitter is carefully designed by integrating the superior v ‐DABNA and BBCz‐DB structures under the auspices of the ingenious short‐range charge‐transfer region regulation strategy. The target tetraboron compound TB‐PB demonstrates a blue emission with an emission maximum of 473 nm, a small FWHM of 12 nm and a CIEy coordinate of 0.14. Benefiting from the emitter's high photoluminescence quantum yield (99%), low excited‐state energy (2.74 eV) and short delayed fluorescence lifetime (0.53 µs), the corresponding OLED achieves exceptional efficiencies of 36.4%, 49.1 cd A −1 , and 51.4 lm W −1 with a record‐high luminescence of 9.0 × 10 5 cd m −2 , an ultra‐narrow FWHM of 15 nm and a CIEy coordinate of 0.20. These breakthroughs will accelerate the development of next‐generation blue emitters and lead to the advancement of OLED technology.