A three boron doped B/O/N multi-resonant TADF emitter for improved reverse intersystem crossing rate and efficient pure blue organic light-emitting diodes

Multiresonant thermally activated delayed fluorescence (MR-TADF) compounds exhibit significant potential as emitters in organic light-emitting diodes (OLEDs) due to their bright, narrowband emission, which provides a solution to the color saturation required by industry for ultra-high definition (UHD) displays. Here, we report the smallest three boron doped MR-TADF emitter (TBDON), a design that fuses two boron-contacting MR-TADF emitters, DOBNA and ADBNA-Me-Mes, together. The resulting emitter, TBDON, shows desirable narrowband pure blue emission (λ_PL = 472 nm with FWHM = 28 nm) and efficient TADF with efficient reverse intersystem crossing (RISC), supported by a relatively fast k_RISC of 7.8 × 10⁴ s⁻¹. The OLED with TBDON showed a high maximum external quantum efficiency (EQE_max) of 24.4%, an EQE of 17.2% at 100 cd m⁻², and Commission Internationale de l’Éclairage (CIE) coordinates of (0.14, 0.16). The ternary device employing DMAC-DPS as an assistant dopant showed improved performance with a higher EQE_max of 28.1% and milder efficiency roll-off with an EQE_100/1000 of 24.4/17.5%. The high device performance demonstrates the promise of the proposed molecular design.