Hyperfluorescence circularly polarized OLEDs consisting of chiral TADF sensitizers and achiral multi-resonance emitters

Developing circularly polarized organic light-emitting diodes (CP-OLEDs) that simultaneously achieve narrow-spectrum emission and high electroluminescence (EL) efficiency remains a formidable challenge. This work prepares two pairs of efficient circularly polarized thermally activated delayed fluorescence (CP-TADF) materials, featuring high photoluminescence quantum yields, short delayed fluorescence lifetimes, good luminescence dissymmetry factors and large horizontal dipole ratios. They can function as emitters for efficient sky-blue CP-OLEDs, providing high maximum external quantum efficiencies (ηext,maxs) (33.8%) and good EL dissymmetry factors (gELs) (−2.64 × 10−3). More importantly, they can work as sensitizers for achiral multi-resonance (MR) TADF emitters, furnishing high-performance blue and green hyperfluorescence (HF) CP-OLEDs with intense narrow-spectrum CP-EL and good ηext,maxs (31.4%). Moreover, tandem HF CP-OLEDs are fabricated for the first time by employing CP-TADF sensitizers and achiral MR-TADF emitters, which radiate narrow-spectrum CP-EL with an extraordinary ηext,maxs (51.3%) and good gELs (4.87 × 10−3). The circularly polarized energy transfer as well as chirality-induced spin selectivity effect of CP-TADF sensitizers are considered to contribute greatly to the generation of efficient CP-EL from achiral MR-TADF emitters. This work not only explores efficient CP-TADF materials but also provides a facile approach to construct HF CP-OLEDs with achiral MR-TADF emitters. The realization of circularly polarized organic light-emitting diodes with narrow-spectrum emission and high efficiency is challenging. Here, authors report an approach for these devices by developing chiral thermally activated delayed fluorescence sensitizers for achiral multi-resonance emitters.