Chiral Thermally Activated Delayed Fluorescence Emitters-Based Efficient Circularly Polarized Organic Light-Emitting Diodes Featuring Low Efficiency Roll-Off

Direct emission of circularly polarized light from organic light-emitting diodes (OLEDs) is a research hotspot as it could increase the efficiency and significantly simplify device architecture of OLED-based 3D displays. In this study, R/S-OBS-Cz and R/S-OBS-TCz with axial chirality were efficiently prepared by using a stable chiral octahydro-binaphthol unit, carbazole/3,6-ditert-butylcarbazole donors, and a 5,5,10,10-tetraoxide acceptor. The chiral unit-acceptor–donor structure provides them not only thermally activated delayed fluorescence (TADF) characteristics with minor singlet–triplet energy gaps of 0.04 and 0.05 eV but also obvious circularly polarized photoluminescence (CPPL) phenomenon with dissymmetry factors of 8.7 × 10^–4 and 6.4 × 10^–4 in codoped films. Meanwhile, the CP-OLEDs prepared by enantiomers exhibit good device performances with the maximum external quantum efficiency reaching 20.3% and ideal efficiency roll-off as well as obvious CPEL properties with a |g_EL| factor up to 1.0 × 10^–3.