High‐Performance Circularly Polarized Electroluminescence with Simultaneous Narrowband Emission, High Efficiency, and Large Dissymmetry Factor

Abstract Organic light‐emitting diodes (OLEDs) that can simultaneously achieve narrowband emission, high efficiency, and circularly polarized luminescence remain a formidable challenge. In this study, a simple strategy is developed to address this challenge. A chiral exciplex‐forming co‐host is first designed by employing a chiral donor and an achiral acceptor molecule. The chiral exciplex host enables an achiral green multiple‐resonance thermally activated delayed fluorescence emitter to achieve high‐performance circularly polarized electroluminescence (CP‐EL) with a high external quantum efficiency of 33.2%, large electroluminescence dissymmetry factor of 2.8 × 10⁻³, and a small full‐width at half‐maximum of 42 nm. This work provides a general approach for realizing CP‐EL using easily available achiral emitters and can significantly extend the scope of circularly polarized OLEDs.