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

Abstract

Circularly polarized organic light-emitting diode (CP-OLED) holds great potential for naked-eye 3D displays, necessitating efficient chiral luminescent materials with optimal CP luminescence (CPL) dissymmetry factor (g). Herein, we present the first chiral multiple resonance thermally activated delayed fluorescence (MR-TADF) material containing 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 peaking 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 |gPL| 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 |gEL| values of 7.0×10-4 and 1.4×10-3, respectively.