Tetraborated Intrinsically Axial Chiral Multi-resonance Thermally Activated Delayed Fluorescence Materials.

Chiral multi-resonance thermally activated delayed fluorescence (CP-MR-TADF) materials hold promise for circularly polarized organic light-emitting diode (CP-OLED) and 3D display. Herein, we present two pairs of tetraborated intrinsically axial CP-MR-TADF materials, R/S-BDBF-BOH and R/S-BDBT-BOH, with conjugation-extended bidibenzo[b,d]furan and bidibenzo[b,d]thiophene as chiral sources, which effectively participate in the distribution of frontier molecular orbitals. Due to the heavy-atom effect, sulfur atoms are introduced to accelerate the reverse intersystem crossing process and increase efficiency of molecules. R/S-BDBF-BOH and R/S-BDBT-BOH manifest ultra-pure blue emission peaking at 458/459 nm with full width at half maximum of 27 nm (0.16 eV), photoluminescence quantum yields of 90%/91% and dissymmetry factors (|gPL|) of 6.8 × 10-4/8.5 × 10-4, respectively. Correspondingly, the CP-OLEDs exhibit good performances with external quantum efficiency of 30.1% and |gEL| factors of 1.2 × 10-3.