3,3'-Substituted Binaphthol-Based Axially Chiral MR-TADF Enantiomers for Solution-Processed Circularly Polarized Organic Light-Emitting Diodes (CP-OLEDs) With External Quantum Efficiency Over 28%

The chiral multi-resonance thermally activated delayed fluorescence (MR-TADF) emitters and circularly polarized organic light-emitting diodes (CP-OLEDs) present great potential for applications in 3D display. However, achieving the simultaneous combination of narrowband emission, high efficiency, and chirality in solution-processable MR-TADF materials through simple methods has consistently proven challenging. The (R/S)-binaphthol chiral unit has been employed in the development of chiral MR-TADF emitters owing to its low cost, easy accessibility, and facile modification. However, current emitters based on the (R/S)-binaphthol unit are predominantly prepared through modification at the 2,2’-position, which suffers from significant steric hindrance, low synthetic yields, and potential adverse effects from intramolecular interactions. Herein, a simple design approach is introduced by directly linking MR-TADF units at the 3,3’-position of the (R/S)-binaphthol, obtaining chiral enantiomers, (R/S)-DBNP, in high yield without chiral resolution. Notably, the solution-processed CP-OLED based on R-DBNP achieved a maximum external quantum efficiency (EQE) of 28.1% and an electroluminescence dissymmetry factors (|g_EL|) value of 2.9 × 10⁻³. The Q-factor (|EQE × g_EL|) of CP-OLED is determined to be 8.1 × 10⁻⁴, which is considerable among solution-processed CP-OLEDs based on small molecules. This simple method reveals the potential for constructing chiral MR-TADF materials for high-performance solution-processed CP-OLEDs, avoiding complicated chiral separation.