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

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, and 51.4 lm W with a record-high luminescence of 9.0 × 10 cd m, 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.