Phosphorus Central Chiral Multiresonance Thermally Activated Delayed Fluorescence Emitter Towards Narrowband and Efficient Circularly Polarized Electroluminescence

For studies concerning circularly polarized multiple resonances thermally activated delayed fluorescence (CP-MR-TADF) emitters with central chirality, only carbon element has been applied. Herein, for the first time, we report a CP-MR-TADF material with phosphorus central chirality containing tert-butyl(phenyl)phosphine oxide, (R/S)-4-POtBuCzB, as enantiomers exhibiting the narrowest full-width at half-maximum (FWHM = 20 nm) among the reported CP-TADF molecules, with symmetric CP photoluminescence and a dissymmetry factor (|g_PL|) of 0.54 × 10⁻³. Concurrently, 2-POtBuCzB further demonstrated that phosphine participated in photophysical performance regulation. Notably, CP organic light-emitting diodes (CP-OLEDs) using (R/S)-4-POtBuCzB showed remarkable CPEL activity with a |g_EL| of 0.61 × 10⁻³, and OLED with 2-POtBuCzB, achieving a maximum external quantum efficiency (EQE_max) of 37.0%. These results demonstrate that introducing chiral phosphorus fragments into the MR-TADF skeleton is an efficacious approach for CP-MR-TADF materials and devices.