Through-Space Coupling Hosts Enhanced Circularly Polarized Electroluminescence Efficiency and Dissymmetry Factor via...

Fabrication of high-performance circularly polarized organic light-emitting diodes (CP-OLEDs) remains greatly challenging, as simultaneous optimization of facile synthesis, easy chiral resolution, high efficiency, and large dissymmetry factor is difficult to realize. Here, we report an innovative chiral host engineering strategy featuring through-space coupling (TSC) skeletons for sensitizing achiral multi-resonance thermally activated delayed fluorescence (MR-TADF) luminogens, which facilitates efficient chiral transfer and superior electroluminescence (EL) performance to resolve the above tradeoff. Two couples of TSC chiral hosts, (R/S)-BNM-2T and (R/S)-BNM-AT, were constructed by connecting (R/S)-binaphthylamine moieties acting as donors and chiral core to diphenyltriazine acceptors of different quantities, avoiding the demand for enantiomeric resolution. These TSC chromophores display intense circularly polarized luminescence, high photoluminescence quantum yields, and efficient exciton harvesting enabled by rapid high-level reverse intersystem crossing. Non-doped CP-OLEDs based on (R/S)-BNM-2T showed EL dissymmetry factors (g_EL) of +7.60 × 10^-3 and -6.73 × 10^-3 at 450 nm. However, using (R/S)-BNM-2T as the host to sensitize achiral MR-TADF emitter (BN2), the resulting devices yielded comparatively high g_EL values up to +1.17 × 10^-2 and -1.06 × 10^-2, accompanied by maximum external quantum efficiency over 21%, suppressed efficiency roll-off, and narrowband emission.