Multiple-resonance thermally activated delayed fluorescence materials based on phosphorus central chirality for efficient circularly polarized electroluminescence.

Circularly polarized organic light-emitting diodes (CP-OLEDs) hold great potential for naked-eye 3D displays, necessitating efficient chiral luminescent materials with an optimal CP luminescence (CPL) dissymmetry factor ( g ). Herein, we present the first chiral multiple resonance thermally activated delayed fluorescence (MR-TADF) materials containing a phosphorus chiral center by incorporating 5-phenylbenzo[ b ]phosphindole-5-oxide into the para -position of two MR-TADF cores. The compounds, NBOPO and NBNPO, exhibit photoluminescence peaks at 462 and 498 nm with narrow full-width at half-maximum values of 25 and 24 nm in toluene, respectively. Notably, ( R / S )-NBOPO and ( R / S )-NBNPO enantiomers display high quantum yields of 87% and 93% and symmetric CPL with | g _PL | factors of 1.18 × 10 ^-3 and 4.30 × 10 ^-3 , respectively, in doped films. Moreover, the corresponding CP-OLEDs show impressive external quantum efficiencies of 16.4% and 28.3%, along with symmetric CP electroluminescence spectra with | g _EL | values of 7.0 × 10 ^-4 and 1.4 × 10 ^-3 , respectively.