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 reported the smallest three boron 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 (PL = 472 nm with FWHM = 28 nm) and efficient TADF with efficiency reverse intersystem crossing (RISC), supported by the relatively fast kRISC of 7.8 × 104 s-1. The OLED with TBDON showed a high maximum external quantum efficiency (EQEmax) 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 hyperfluorescent device employing DMAC-DPS as an assistant dopant showed improved performance with a higher EQEmax of 28.1% and milder efficiency roll-off with EQE100/1000 of 24.4/17.5%. The high device performance demonstrates the promise of the proposed molecular design.